Pest management

1. Introduction

Pests can attack soybean crops at any stage from seedlings to harvest, but crops are most attractive to insect pests from flowering onwards. Soybean crops are more tolerant of insect damage than most other grain legumes and noticeable damage (particularly leaf damage) does not necessarily result in yield loss. The basic Integrated Pest Management (IPM) strategy for soybean crops is to avoid non-selective pesticides for as long as possible to foster a build-up of predators and parasites, i.e. to ‘GO SOFT EARLY’. This buffers the crop against pest attack during later crop stages, and greatly reduces the risk of subsequent helicoverpa, silverleaf whitefly and mite attack. However, many pests have a major impact on yield and quality, and intervention with pesticides is frequently unavoidable. This manual covers through all aspects of soybean pest management.

Major pests in soybean crops are helicoverpa (heliothis), podsucking bugs, and potentially silverleaf whitefly. Other lesser and/or infrequent, but damaging pests, include loopers, grass blue butterfly, cluster caterpillar, soybean moth, soybean aphid, mirids, monolepta beetle and crickets. Note that bean podborer and beanfly, both major pests in other summer pulses, are not a threat to soybean crops. However, soybean stemfly, can cause significant damage leading to plant death in stressed crops, but (luckily) is only a pest of spasmodic occurrence.

Soybean plants are more attractive to a range of foliage-feeding pests (e.g. numerous loopers, grass blue butterfly, and leaf miners) than other summer pulses. During the vegetative stage, 33% leaf defoliation can be tolerated without yield loss, although this falls to 16% during pod set.

Helicoverpa can attack at any stage from seedlings onwards. Helicoverpa can severely damage drought-stressed vegetative crops because they are then more likely to attack the plant’s axillary buds, the precursors to the floral buds. The reason for this is that the leaves in droughted plants are drier and less palatable. Soybean plants can compensate for considerable damage during early podding because they set a large number of ‘reserve pods’ that can replace pods eaten by helicoverpa.

Fall armyworm (FAW) is a new pest that occasionally attacks soybean crops. The most common scenario is where a soybean crop is planted into land with FAW-infested weeds, or if FAW-infested maize/sweet corn self-sets are sprayed out with herbicides. In both scenarios, FAW larvae move from their dying hosts to the adjacent soybean plants. To date, there have been no reports of FAW laying eggs on soybean plants.

Podsucking bugs (PSB) are major soybean pests. The most damaging species are the green vegetable bug (Nezara viridula), large and small brown bean bugs (Riptortus and Melanacanthus sp. respectively) and the redbanded shield bug (Piezodorus oceanicus). Podsucking bugs damage seeds from pod fill to pod ripening and the thresholds are based on reduced seed quality. Only 3% seed damage is tolerated in edible soybeans, and the PSB threshold in edibles is set at 2% damage to allow a 1% safety barrier to avoid immediate downgrades of ≥$100/t once damage exceeds 3%.

Silverleaf whitefly (SLW) are a potential threat to soybean crops. However, the introduced SLW parasite, Eretmocerus hayati, native parasites and predators, have largely stabilised whitefly populations in most regions in most years. Note that beneficials targeting SLW are only effective if they are not disrupted by non-selective pesticides, particularly in vegetative and flowering crops.

Soybean aphids are present in most crops but are mostly kept in check by ladybirds and hoverfly larvae. Above-threshold soybean aphid populations (>250 aphids per plant) can have a devastating impact on yield and harvest maturity.

Mirids have far less impact in soybean crops than in mungbean crops. Up to 5 mirids/m² have no impact on yield.

Other pests that spasmodically occur in very damaging numbers include monolepta beetle in coastal sugar-growing regions, and soybean moth larvae (which mine inside the leaves) in all regions.

Scout crops regularly with a beat sheet, at least weekly pre-flowering, and twice weekly post-flowering. In a typical soybean crop, budget for one deltamethrin spray for podsucking bugs, and one helicoverpa spray after flowering, preferably with a moderately selective pesticide such as indoxacarb. Check all registrations regularly on the APVMA/PUBCRIS website and only use products registered or under permit in soybean crops. 

2. Integrated pest management (IPM) in soybean crops

IPM is the term used for a wide range of tactics to (a) prevent pests from reaching damaging levels in crops and (b) if they do so, to manage the target pest in a way that is less likely to flare other pests such as silverleaf whitefly. By using a wide range of tactics to deal with pests, IPM removes the reliance on a single method of control, such as insecticides. IPM tactics include:

• Conservation of natural enemies and introduced biological control agents.

• Using soft selective pesticides and biopesticides.

• Regular crop monitoring of pest and beneficial insects.

• Using Economic Thresholds to rationalise pesticide use and avoid uneconomic sprays.

• Host plant resistance (e.g. not spraying at crop stages when the crop is able to tolerate or compensate for significant pest damage), and planting resistant cultivars.

• Cultural practices e.g. agronomic practices that promote vigorous crops better able to tolerate pest attack, and crop hygiene.

• Area Wide Management to maximise the benefits of IPM practices.

The benefits of IPM are many and varied, and include:

• Regular scouting allows early detection of potential problems so timely action can be taken.

• IPM results in the strategic use of chemicals, which reduces the health risks to growers and consumers.

• Strategic use of chemicals minimises the chance of pests developing resistance to pesticides.

• Reduced negative impact on the environment.

• The use of soft pesticides conserves natural enemies to manage pests for free.

• IPM leads to a more robust sustainable system that does not rely on one control method.

• IPM allows growers to control insect pests in a more cost-effective way.

2.1   IPM and pesticides

IPM does not necessarily mean the abandonment of pesticides for controlling pests. However, IPM aims to reduce the frequency of pesticide applications. The use of thresholds ensures sprays are applied only when required. Overuse of pesticides hastens the development of insecticide resistance, can lead to a resurgence of target pests, can create new pests, may increase residues in harvested seed, and increases off-target contamination.

Soft and hard pesticides

The adjectives ‘soft’ or ‘selective’ are frequently applied to pesticides in the context of IPM. Soft or selective pesticides kill pests but have a minimal impact on beneficial insects attacking these pests. In contrast pesticides that impact on natural enemies are termed ‘hard’, ‘non-selective’ or ‘broad spectrum’.

In practice there are varying degrees of softness and many products may be hard on one group of natural enemies, but relatively soft on another. The term ‘soft’ does not imply a product to be of low toxicity to mammals, although many of the softest products, particularly bio-pesticides, have little or no impact on humans and other mammals.

The ‘hardness’ of a product can sometimes be mitigated by reducing the rate (where there is data showing no reduction in efficacy), or by delaying spraying for as long as possible. In general, the later in the life of a crop a hard spray is applied, the less the likelihood of it flaring other pests because there is less time between application and harvest.

IPM and organics

IPM is not necessarily the same as organic pest management. Many, but not all, organic options are compatible with IPM. For example, many botanically derived products such as pyrethrum adversely affect beneficial insects. Another organic product, NEEM, contains an active ingredient that affects female reproduction in mammals.

IPM and biological control

IPM is sometimes confused with classical biological control. Classical biological control involves the importation and release of exotic control agents (predators and parasites) to control (usually) exotic pests. This practice is used because there are no native control agents, or because the native ones are (or thought to be) ineffective.

IPM plays an important role in maximising the success of classical biological control. The reduction in the use of non-selective chemical sprays increase the survival of introduced control agents and hence their effectiveness and improves their chance of establishment in a new environment.

One example of classical biological control in Australia is the introduction of the Cactoblastis moth to control prickly pear. A recent example in soybean and other crops is the release of a small parasitic wasp, Eretmocerus hayati to control silverleaf whitefly.

2.2 The soybean IPM strategy

The basic IPM strategy for soybean crops is to avoid non-selective pesticides for as long as possible in order to foster a build-up of predators and parasites, i.e. ‘GO SOFT EARLY’. This helps keep early pests in check and buffer the crop against pest attack during later crop stages. This is particularly important for soybean crops because of the whitefly risk.

However, intervention may be required during podding, especially against podsucking bugs populations of which peak during late pod fill. Podsucking bugs cannot be ignored as they drastically reduce seed quality, as well as yield. Over 90% of seeds can be damaged if above-threshold bug populations are left unchecked.

Regular monitoring of pest numbers is critical in soybean crops, especially with the onset of flowering and throughout podding, when crops become attractive to podsucking bugs, helicoverpa and other pests. The other critical IPM strategy is to only spray above-threshold populations.

What is needed for IPM to work?

Successful implementation of IPM requires growers to have knowledge of key components in the field that will guide sound decisions and forecasts.

These include:

• Accurate pest and beneficial insect identification.

• Understanding pest life cycles, biology and ecology,

• Understanding the impact of pest damage on crop quality and yield at different pest densities and being aware of the thresholds for specific pests.

• Knowing the effects of control methods on target pests, non-target pests and beneficial insects.

• Knowing what products are registered or under permit in soybean crops.

Much of the essential knowledge can be gained from regular crop inspections, good record keeping and reading published information such as this manual. 

3. Major soybean pests: identification, biology, damage and natural enemies

3.1 Helicoverpa, Helicoverpa armigera, H. punctigera

Pest status: Helicoverpa can severely damage all soybean crop stages and all plant parts. Vegetative soybean plants are more attractive to helicoverpa than other summer pulses and soybean plants can even be damaged during the seedling stage. However, the crop is normally at greatest risk of attack from flowering to late pod fill. From southern Queensland northwards, soybean crops are at greatest risk from H. armigera from December onwards.

Identification: Helicoverpa larvae can be confused with loopers, armyworms (including fall armyworm) or cluster caterpillars. Their colour is very variable ranging from green to orange to brown to black. Look for a broad pale band along each flank, a lack of large dark spots, four pairs of abdominal prolegs, sparse body hairs and a parallel body. Young H. armigera larvae have a dark saddle behind the head while H. punctigera larvae don’t. Large H. armigera larvae have white hairs behind the head. Larvae can reach 35 mm in length.

Helicoverpa moths have a 35 mm wingspan. The forewings of males are straw-colour and those of females are brown. Forewings of both sexes have dark markings. Hindwings are pale cream with a wide, dark outer band. H. armigera has a distinctive pale spot in the hindwing’s dark outer band. This spot is missing in H. punctigera.

Refer also to Helicoverpa identification: https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/biosecurity/plants/insects/field-crop/helicoverpa

Damage: Helicoverpa defoliation is characterised by rounded chew marks and holes, (loopers make more angular holes). Helicoverpa also attack axillary buds and terminals in vegetative crops. This type of damage can have a severe impact on subsequent pod set, particularly if there are high populations in seedling or drought-stressed crops. Early terminal and bud damage can also result in pods being set closer to the ground. Such pods are more difficult to harvest. In drought-stressed crops, the last soft green tissue is usually the vegetative terminals, which are thus more likely to be totally consumed than in normally growing crops.

Once crops reach flowering, larvae focus on buds, flowers and pods. Young larvae are more likely to feed on vegetative terminals, young leaves and flowers before attacking pods. Small pods may be totally consumed by helicoverpa, but larvae target seeds in large pods. Crops are better able to compensate for early than late pod damage. However, in drought-stressed crops, early damage may delay or stagger podding with subsequent yield and quality losses. Damage to well-developed pods also results in the weather staining of uneaten seeds due to water entering the pods.

Monitoring: Beat sheet sampling is the preferred sampling method for medium to large helicoverpa larvae. Small larvae should also be scouted for by inspecting (opening) vegetative terminals and flowers. Damage to vegetative terminals is often the first visual clue that helicoverpa larvae are present. Soybean crops should also be scouted for eggs and moths, to pinpoint the start of infestations and increase the chance of successful control.

Inspect crops at least weekly in the vegetative stage and twice-weekly from early budding until late podding. Sampling twice-weekly increases the chance of detecting caterpillar pests while they are still small enough to be easily controlled.

Sample six widely spaced locations per crop management unit. Take 5 x 1 m long samples at each site with a ‘standard’ beat sheet. Convert larval counts/m to larvae/m² by dividing counts by the row spacing in metres.

Beat sheet sampling may only detect 50% of small larvae in vegetative and podding soybean plants, and 70% during flowering, as they feed in sheltered sites such as leaf terminals. However, many of these small larvae will be lost to natural mortality factors before they reach a damaging size, and in most crops, this mortality will cancel out any sampling inefficiencies.

For more information on the beat sheet technique: https://thebeatsheet.com.au/bigger-is-not-better-when-it-comes-to-beat-sheet-sampling/

Thresholds: In vegetative crops, thresholds for many leaf feeding pests are expressed as % tolerable defoliation or % tolerable terminal loss. Before flowering, soybean plants can tolerate up to 33% leaf loss without loss of yield. However, DAF trials (Rogers and Brier 2010) show that helicoverpa populations inflicting less than 33% damage can still cause serious yield loss because the larvae not only feed on leaves, but also attack terminals and axillary buds. The data indicates an economic threshold of 7.5/m² helicoverpa larvae in mid to late vegetative soybean crops. This threshold should be lowered in early vegetative or stressed crops. Helicoverpa thresholds for podding soybean crops currently range from 1–3 larvae/m² (depending on crop value and the cost of pesticide plus application).

Chemical control: Unless there are very high populations prior to flowering, biopesticides, particularly helicoverpa nuclear polyhedrosis virus (NPV), are recommended in preference to chemical insecticides. This helps conserve beneficial insects to buffer crops against helicoverpa attack during the susceptible reproductive stages and avoids flaring of other pests such as silverleaf whitefly and mites. During the flowering to pod fill stages, registered chemical insecticides are chlorantraniliprole (Vantacor – Group 28) ), indoxacarb (Steward – Group 22) and emamectin (Affirm – Group 6). If multiple sprays are required, rotate pesticide groups, and apply each group only once per crop.

For more information, please refer to: Resistance management strategy for Helicoverpa armigera in Australian grains https://ipmguidelinesforgrains.com.au/important/uploads/GRDC_RMS_Helicoverpa-Armigera.pdf  

Always check the APVMA website for the latest registrations and permits: https://apvma.gov.au/node/10831

Cultural control: Where possible, avoid successive plantings of summer legumes. Good agronomy and soil moisture are crucial as large, vigorously growing plants suffer less defoliation for a given helicoverpa population and have less risk of terminal damage.

In water-stressed crops, terminals are more attractive to larvae than wilted leaves. Vigorously growing plants with adequate available moisture are better able to replace damaged leaves and to compensate for flower and pod damage.

Natural enemies: The number of beneficial varies with crop age, from crop to crop, region to region, and from season to season. The combined action of several beneficial species is often required to have a significant impact on potentially damaging helicoverpa populations. It is therefore desirable to conserve as many beneficials as possible.

Natural enemies of helicoverpa include predators of eggs, larvae and pupae, parasites of eggs, larvae and pupae, and caterpillar diseases. Predatory bugs and beetles attacking helicoverpa eggs and larvae include: spined predatory bug, glossy shield bug, damsel bug, bigeyed bug, apple dimpling bug, assassin bugs, red and blue beetle, and predatory ladybirds. Other important predators include ants, spiders and lacewings. Egg parasites include the tiny Trichogramma spp. wasps. Caterpillar parasites include Microplitis, Heteropelma and Netelia sp. wasps and several species of tachinid flies, including Carcelia sp. The banded caterpillar parasite Ichneumon promissorius is actually a pupal parasite.

For more detail, see: 

• ‘Insects: Microplitis demolitor and ascovirus: important natural enemies of helicoverpa’ https://www.daf.qld.gov.au/__data/assets/pdf_file/0011/50699/Insects-Microplitis-ascovirus.pdf

• Good bug? Bad bug? https://thebeatsheet.com.au/wp-content/uploads/2012/06/GoodBadBug-Mar2013-lowres.pdf

With the exception of the egg parasites and Microplitis, most parasites don’t kill helicoverpa until they reach the pupal stage. Predatory earwigs and wireworm larvae are significant predators of helicoverpa pupae.

Naturally occurring caterpillar diseases frequently have a marked impact on helicoverpa in summer legumes. Outbreaks of NPV are frequently observed in crops with high helicoverpa populations. Fungal outbreaks are also often observed in wetter seasons.

3.2 Podsucking bugs

Podsucking bugs can move in at budding but significant damage is confined to pods from early pod fill to harvest maturity. While bugs start breeding as soon as they move into flowering crops, nymphs must feed on pods to complete their development. Early bug damage results in shrivelled and distorted seeds, which can severely reduce yield and seed quality. However, many early damaged seeds are lost at harvest (because they are small), and thus don’t contribute to reduced seed quality. Also, soybean plants can compensate for the potential yield loss linked to these lost seeds, by re-directing assimilate into the remaining undamaged seeds, which consequently increase in size. Unless populations are very high, the potential yield loss from early damage is totally compensated.

However, later damaged seeds are only slightly distorted and are retained at harvest. Note that bugs can even damage seeds in pods nearing harvest maturity. These seeds lack any distortion but have noticeable sting marks. In all, late bug damage reduces seed quality but not yield. As only 3% seed damage is tolerable in culinary soybeans, bug thresholds are based on seed quality, not seed yield. Note that once the 3% damage is passed, penalties of ≥$100/t apply.

Several podsucking bug species attack soybean crops and include:

• green vegetable bug

• redbanded shield bug

• large brown bean bug

• small brown bean bug

• brown shield bug

The green vegetable bug (GVB) and the brown bean bugs are equally damaging to crops, while the damage potential of the redbanded and brown shield bugs are 0.75 and 0.7 of a GVB, respectively. Nymphs of all species are less damaging than adults. While 1st instar nymphs cause no damage, subsequent instars are progressively more damaging with the 5th and final instar being nearly as damaging as adults. To determine the damage potential of mixed bug species populations, convert all species (adults and nymphs) to GVB adult equivalents (GVBAEQ). https://thebeatsheet.com.au/economic-threshold-calculators/economic-thresholds-for-podsucking-bugs/

Green vegetable bug (GVB), Nezara viridula 

Distribution: GVB was first recorded in Australia in 1916 (an accidental introduction) and is now found in all Australia states and territories.

Pest status: Major, widespread and regular. GVB is the most damaging podsucking bug in pulses, due to its abundance, widespread distribution, rate of damage and rate of reproduction. It is one of the most recognised agricultural pests in Australia.

Identification: Adult GVB are bright green and shield-shaped. They are 13–15 mm long. Adult GVB have three small white spots at the front of the scutellum (between their shoulders). Yellow and orange GVB colour variants are occasionally encountered. Over wintering adults are purple-brown in colour. GVB emit a foul smell when disturbed to deter predators.

GVB eggs are laid in rafts (50–100 eggs per raft) and are circular in cross-section. Newly laid eggs are cream but turn bright orange prior to hatching. Parasitised GVB eggs are black.

GVB nymphs vary in colour. Newly hatched nymphs (1.5 mm long) are orange and brown (sometimes black). Later instars are green or black, with white, cream, orange and red markings. Final (5th) instar nymphs have fewer spots (more base colour, green to black), and have prominent wing bugs. Younger nymphs are round or oval rather than shield shaped and usually aggregate in large clusters. Older nymphs are more widely dispersed.

Life cycle: Eggs take 6 days to hatch at 25°C. Nymphs don’t usually reach a damaging size until mid to late pod fill. Usually only one generation develops on a summer legume crop. Nymphs require pods containing seeds to complete their development and the podding phase of most summer legumes is only slightly longer in duration than GVB life cycle. There are five nymphal instars with a total development time of about 30 days. Development is faster at temperatures higher than 25°C but there is considerable nymphal and adult mortality at temperatures over 35°C.

Risk period: Adult bugs typically invade summer legumes at flowering, but GVB is primarily a pod feeder with a preference for pods with well-developed seeds. Nymphs are unable to complete their development prior to pod fill. Soybean crops remain at risk until pods are too hard to damage (i.e. very close to harvest). Damaging populations are typically highest in late summer crops during late pod fill (when nymphs have reached or are near adulthood).

Damage: Pods most at risk are those containing well-developed seeds. While GVB also damages buds and flowers, soybean plants can compensate for this early damage. Damage to young pods cause deformed and shrivelled seeds and potentially reduces yield, although this is often compensated for by an increase in weight of undamaged seeds. Seeds damaged in older pods are blemished and difficult to grade out, reducing harvested seed quality, particularly that destined for human consumption (edibles). GVB can even damage seeds in ‘close-to-harvest’ pods (i.e. pods that have hardened prior to harvest). Bug-damaged seeds have increased protein content but reduced oil content and a shorter storage life (due to increased rancidity). Bug-damaged seeds are frequently discoloured, either because of tissue breakdown, or diseases such as Cercospora (purple seed stain), which may gain entry where bugs have pierced pods.

Small GVB nymphs are far less damaging than older nymphs, which become progressively more damaging as they progress to adulthood. Final instar nymphs are nearly as damaging as adults.

Sampling and monitoring: Inspected crops twice-weekly for GVB from flowering until close to harvest. Sample crops for GVB in the early to mid morning. Beat sheet sampling is the only effective monitoring method. The standard sample unit is five 1 m non-consecutive lengths of row within a 20 m radius. Convert all bug counts per row metre to bugs/m² by dividing counts per row metre by the row spacing in metres.

Sample at least six sites throughout a crop management unit to accurately determine adult GVB populations. GVB nymphs are more difficult to sample accurately as their distribution is extremely clumped, particularly during the early nymphal stages (1st to 3rd instars). Ideally, sample at least 10 sites (with five non-consecutive row metres sampled per site) to adequately assess nymphal populations.

Thresholds: Podsucking bug thresholds in edible or culinary soybeans (destined for human consumption) are determined by seed quality, the maximum bug damage permitted being only 3%. GVB thresholds range is typically 0.3–0.8/m² depending on the crop size (seeds per m²) and when bugs are detected. Because thresholds are determined by % damage, the larger a crop (the more seeds per unit area), the more bugs required to inflict critical (threshold) damage, and the higher the threshold. For crushing and stockfeed soybeans with lesser quality requirements, the threshold is doubled. Thresholds are expressed in adult equivalents.

To determine the damage potential of mixed bug species populations, convert all species (adults and nymphs) to GVB adult equivalents (GVBAEQ). https://thebeatsheet.com.au/economic-threshold-calculators/economic-thresholds-for-podsucking-bugs/

Chemical control: Bugs should be controlled during (but not prior to) early pod fill before nymphs reach a damaging size. Pesticides are best applied in the early to mid morning to contact bugs basking at the top of the crop canopy. GVB are easily controlled with deltamethrin.

Cultural control: Avoid sequential plantings of summer legumes as bug populations will move progressively from earlier to later plantings, eventually building to very high levels. Avoid cultivar and planting time combinations that are more likely to lengthen the duration of flowering and podding.

Natural enemies: GVB eggs are frequently parasitised by a tiny, introduced wasp Trissolcus basalis. Parasitised eggs are easily recognised as they turn black. GVB nymphs are attacked by ants, spiders and predatory bugs. Final (5th) instar and adult GVB are parasitised by the recently introduced tachinid fly (Trichopoda giacomellii).

Redbanded shield bug (RBSB), Piezodorus oceanicus

Redbanded shield bugs in Australia were previously classified as Piezodorus hybneri and more recently as P. grossi.

Pest status: Major, widespread, regular. RBSB is 75% as damaging as GVB in summer pulses and is more difficult to control with current pesticides. In more southern regions (SEQ, SQ and NSW), RBSB are usually not as abundant as GVB. However, in the tropics, very high RBSB populations have been reported in soybean crops and other pulses.

Identification: Adults are similar in shape to GVB but are smaller (8–10 mm long) and paler, with a noticeable band across their shoulders. Females have a pink (not red) band across their shoulders. In contrast, males have an off-white band across the shoulders and pale yellow lines along their side. However, in the tropics, many females also have white transverse bands.

Eggs are laid in distinctive twin row rafts with 15–40 dark elliptical eggs (in cross-section), ringed with small spines. Newly hatched nymphs are orange with black markings and similar to newly hatched nymphs of many other shield bugs. Larger nymphs are pale green with dark red and brown markings in the centre of their back. Late autumn nymphs may turn a pale pink-brown colour.

Damage: Damage is similar to that caused by GVB, with early damage reducing yields, and later damage reducing the quality of harvested seeds.

Thresholds: Convert to GVB equivalents to determine their damage potential i.e. multiply Piezo counts by 0.75.

To determine the damage potential of mixed bug species populations, convert all species (adults and nymphs) to GVB adult equivalents (GVBAEQ). https://thebeatsheet.com.au/economic-threshold-calculators/economic-thresholds-for-podsucking-bugs/

Monitoring: As for GVB. Look for the distinctive dark twin-row egg rafts that indicate RBSB presence.

Chemical control: No insecticides are specifically registered against RBSB in Australia but clothianidin (Shield) can be used against this pest under PER86221*. For best results (>80% control), always add a non-ionic surfactant (e.g. MAXX) and a 0.5% w:v salt adjuvant. Note that deltamethrin alone gives zero control of RBSB and only 50–60% control with the addition of the 0.5% w:v salt adjuvant. However, better control can be achieved with a deltamethrin/methomyl mix (0.5 and 1.5 L/ha respectively), giving 80% control of RBSB, again with the addition of a 0.5% salt adjuvant.

* Note when searching for permit details, type in the Permit number, not ‘Shield’.

Natural enemies: Spiders, ants, and predatory bugs are major predators of RBSB, particularly of eggs and young nymphs with mortality of these stages sometimes exceeding 90%. Eggs may be parasitised by the tiny wasp, Trissolcus basalis. Adults are infrequently parasitised by the recently introduced tachinid fly Trichopoda giacomellii.

Large brown bean bug, Riptortus serripes

Hemiptera: Alydidae 

Distribution: Native to Australia.

Similar Riptortus species occur in Asia, India and Africa.

Pest status: Major. As damaging as GVB. More frequent on the coast, with a liking for the Vigna legumes, e.g. adzuki, cowpea and mungbean, as well as soybean.

Identification: An elongated dark brown bug, 16–18 mm long (not including legs and antennae) with long antennae and a bright yellow stripe along each side. This stripe is more pronounced in males and less distinct in females, which have a ‘rounder’ body than males. Riptortus serripes’s body narrows in the middle and it has a spine on each ‘shoulder’. It also has large robust and spiny hindlegs. When it is flying, the bright orange top of the abdomen is revealed.

Nymphs are dark brown and similar in outline to ants. Close inspection shows they lack the very narrow ‘waist’ and biting mouthparts (jaws) typical of ants.

Eggs are a dark purple-brown in colour and are laid singly or in small clusters. They are slightly elliptical with a flattened top and rounded base and are 1.5 mm long.

May be confused with:

• Small brown bean bug, Melanacanthus scutellaris, which is considerably smaller (10–12 mm) and not as robust.

• Rice or paddy bug Leptocorisa acuta (Thunberg). Rice bugs are pale green or brown, reach 15 mm in length, and are very slender with thin hindlegs.

Life cycle: Riptortus invade summer legumes at flowering and proceed to feed and lay eggs. This pest lays scattered single eggs. There are five nymphal stages with nymphs reaching a damaging size during mid to late pod fill. Development times for Riptortus eggs and nymphs are about 8 and 17 days respectively (25 days total) at 26°C. Overwintering R. serripes shelter in curled up dead leaves.

Host range, risk period and damage: As for GVB. R. serripes is as damaging as GVB

Monitoring: The beat sheet method is not totally satisfactory for R. serripes because it is very flighty, particularly during the hotter parts of the day. Crops should be sampled during the early morning. Crop scouts should also familiarise themselves with the appearance of flying (and escaping) Riptortus adults and include these in sampling counts.

To determine the damage potential of mixed bug species populations, convert all species (adults and nymphs) to GVB adult equivalents (GVBAEQ). https://thebeatsheet.com.au/economic-threshold-calculators/economic-thresholds-for-podsucking-bugs/

Chemical control: Riptortus serripes is likely to be controlled by synthetic pyrethroids that are registered against GVB.

Small brown bean bug, Melanacanthus scutellaris

Hemiptera: Alydidae

Distribution: Native to Australia.

Pest status: Major. This pest can be as damaging as GVB.

Identification: The small brown bean bug is an elongated brown bug, 10–12 mm long (body only) with long antennae and a cream stripe along each side. This stripe is often less distinct in females, which are ‘rounder’ than males. Males also have a prominent pale patch in the scutellum. The small brown bean bug has a short spine on each ‘shoulder’ (less pronounced than on Riptortus sp.), and moderately robust and spiny hind legs (thinner than those of Riptortus sp.).

Nymphs are dark brown to black and similar in outline to ants. Close inspection shows they lack the very narrow ‘waist’ typical of ants. The shiny olive green eggs are laid in small clusters. The eggs are slightly elliptical with a flat top and a rounded base and are 1.0 mm long.

Life cycle: Small brown bean bugs invade summer legumes at flowering where they commence feeding and lay eggs. This bug lays scattered single eggs (up to several hundred per female). There are five nymphal stages and nymphs usually reach a damaging size to coincide with mid to late pod fill. Development times for eggs and nymphs are about 6 and 20 days respectively at 26°C.

Damage: The small brown bean bug is as damaging as GVB and the large brown bean bug.

Monitoring and control: As for the large brown bean bug Riptortus serripes.

To determine the damage potential of mixed bug species populations, convert all species (adults and nymphs) to GVB adult equivalents (GVBAEQ). https://thebeatsheet.com.au/economic-threshold-calculators/economic-thresholds-for-podsucking-bugs/

Brown shield bug, Dictyotus caenosus (Westwood)

Hemiptera: Pentatomidae 

Distribution: Native to Australia.

Pest status: Minor but difficult to control pest.

Identification: Brown shield (or brown stink) bug (BSB) adults are shield shaped and are matt mid brown (i.e. not glossy). At 8 mm long, they are noticeably smaller than the green vegetable bug.

Newly hatched nymphs are orange with black markings and similar to newly hatched nymphs of many other shield bugs. Larger nymphs have a dark brown (sometimes almost black) head and thorax, and a pale brown abdomen with transverse dark brown and pale (almost white) markings at its centre. There is also a transverse pale band at the front of the abdomen. BSB lays eggs in either small twin rows or small irregular rafts containing 10–16 eggs. Eggs are pale cream and similar in shape to GVB eggs.

May be confused with: Glossy shield bugs (Cermatulus nasalis), which are slightly larger and a predatory species. Brown shield bug eggs and nymphs are distinct from those of Cermatulus.

Life cycle: BSB invade summer legumes at flowering and proceed to feed and lay eggs. Nymphs usually reach a damaging size during mid to late pod fill. There are five nymphal stages.

Damage and control: The brown shield bug damages 75% as many seeds as GVB. Preliminary trials show this species is (like Piezodorus) also difficult to control with current pesticides but that control with deltamethrin can be improved (to 50–60%) with the addition of a 0.5% salt (NaCl) adjuvant.

To determine the damage potential of mixed bug species populations, convert all species (adults and nymphs) to GVB adult equivalents (GVBAEQ). https://thebeatsheet.com.au/economic-threshold-calculators/economic-thresholds-for-podsucking-bugs/

3.3 Silverleaf whitefly (SLW), Bemisia tabaci biotype B.

Silverleaf whitefly (SLW) poses a threat to soybean crops in most regions in NE Australia. However, the exotic SLW parasite Eretmocerus hayati, together with native parasites and predators, can stabilise SLW populations, provided they are not disrupted by the overuse of non-selective pesticides.

Distribution: SLW is widespread in tropical and subtropical Australia. In southern Queensland and northern NSW, SLW is most abundant in coastal regions with milder winters and a continuum of hosts. However, SLW is also abundant in more-inland regions such as the Emerald irrigation area of Central Qld, the St George irrigation area of SW Qld, and the north-west slopes of NSW.

Pest status: Always a potential major risk in a susceptible crop such as soybean, particularly in regions where broad-spectrum insecticides are widely used.

Identification: Adults are 1.5 mm long with powdery white wings and a pale orange body. Their folded wings don’t quite touch, revealing the body when viewed from above. SLW eggs are small and spherical and sit on a short stalk. Eggs are initially pale yellow but turn brown with age. High egg densities give the impression the underside of the leaf is covered with brown velvet. The nymphs (or scales) are pale cream/yellow and are flat and oval shaped. Nymphs cease feeding and metamorphose to winged adults during the late 4th instar, which is called the pupa or ‘red eye’ (because of prominent red eye spots). The life cycle takes 18 to 30 days from egg lay to adult depending on temperature.

May be confused with: SLW can only be differentiated from other strains of Bemisia tabaci by biochemical testing. The larger greenhouse whitefly (1.5 mm) has wings that obscure the body when viewed from above and a nymphal stage with long waxy filaments.

Host range: Of the summer pulses, soybean and navy bean are preferred SLW hosts. Other favoured hosts include capsicum, cotton, cucurbit, dolichos, milk thistle, poinsettia, rattlepod, sunflower, sweet potato and tomato.

Risk period: Soybean crops maturing during late summer and autumn are at greater risk of attack because invading SLW have had more time to increase from low overwintering populations. As a rule, the earlier crops are infested the greater the risk. Crops remain attractive to SLW until mid pod fill. As photosynthetic assimilates are redirected from leaves to fill the pods, leaves become unattractive to SLW and adults leave the crop to find more attractive hosts.

Damage: SLW can reduce plant vigour and yield by the sheer weight of numbers removing large amounts of plant photosynthate from the leaves. Severe infestations in young plants can stunt plant growth and reduce yield potential. Later infestations can reduce the number of pods set, seed size, and seed size uniformity, thus reducing yield and quality. As a rule, the impact of SLW is worst in drought-stressed crops. In heavily infested soybean crops, both pods and seeds are often unusually pale. While seed colour is unlikely to be of concern in grain soybean (harvested seeds being naturally pale), pod and seed discolouration are a major marketing problem where pods are picked green, e.g. vegetable soybeans and green beans.

SLW often secrete large amounts of sticky honeydew. Adult females produce more honeydew than other stages and nymphs produce more honeydew when feeding on stressed plants. Honeydew itself is not a major problem, but sooty mould developing on honeydew shields leaves from sunlight and reduces photosynthesis. The impact of sooty mould is greatest from early to mid pod fill when SLW activity is mainly at the top of the canopy, i.e. on leaves with the greatest photosynthetic activity. Rain and overhead irrigation wash honeydew off leaves, lessening the risk of sooty mould.

Monitoring: SLW eggs, nymphs and resting adults are mainly found on the underside of leaves. Flying SLW adults are readily observed when crops with high populations are disturbed. The presence of honeydew and sooty mould may also indicate SLW attack, but can be due to aphid feeding. SLW eggs are laid on younger leaves, so by the time eggs develop to large nymphs in crops with high growth rates, leaves with the greatest visible SLW nymphal activity are further down the plant. This may be as many as 5–7 nodes below the plant top. As vegetative growth slows, plant nodes with greatest nymphal activity move progressively upwards to the canopy top.

Thresholds and chemical control: There are no validated thresholds for SLW and no pesticides are specifically registered for SLW control in summer pulses in Australia. Use the softest options possible for other pests, especially early in the life of the crop, to encourage SLW parasites and predators.

Cultural control: Where possible, avoid successive plantings of summer pulses to prevent movement from early to late crops. Avoid planting summer pulses near earlier maturing SLW hosts such as cotton and cucurbits. Where damaging SLW populations are evident in other crops early in the season (early summer), or in regions with a history of consistently damaging and widespread SLW activity, consider planting a pulse type less attractive to SLW, e.g. mungbean or adzuki (Vigna sp.), rather than soybean. However, in most regions, this should not be necessary.

Control SLW weed hosts such as rattlepod and milk thistle. Irrigate crops to reduce moisture stress to make crops less susceptible to SLW damage. Overhead irrigation also washes off sooty mould and drowns adult SLW. Narrow leafed and smooth leafed (less hairy) cultivars may be less attractive to SLW. However, the latter attribute may leave crops more vulnerable to aphid attack.

Natural enemies: SLW nymphs are parasitised by native species of Encarsia and Eretmocerus (both very small wasps). In the early to mid 2000s, CSIRO made widespread releases of the exotic parasite Eretmocerus hayati. The parasite is now well established and, in conjunction with native SLW parasites and predators, has stabilised SLW populations in many soybean crops. Nymphs parasitised by Eretmocerus are an opaque honey colour while those parasitised by Encarsia are dark. Look for discoloured nymphs to monitor SLW parasitism in your crop.

4. Moderate, less frequent and minor pests

There are several pests considered moderate, less frequent or minor in soybean crops. These include:

Cluster caterpillar, Spodoptera litura 

(often referred to as ‘spods’)

Distribution: Cluster caterpillar is more common in tropical and coastal regions.

Pest status: Moderate. Not as damaging as helicoverpa and less frequent. It has been reported as causing significant defoliation to soybean crops in coastal Qld.

Identification: Moths are larger than helicoverpa with a 40 mm wingspan and have brown forewings with criss-cross cream streaks.

The eggs are laid in a furry cream mass on the underside of leaves. Young larvae ‘cluster’ together and are translucent green with a darker thorax. Middle-sized larvae are smooth skinned with a pattern of red, yellow, and green lines, a dark patch on the hump behind the head, and dark spots along each side. Large larvae are initially brown with three thin pale yellow lines down the back: one in the middle and one on each side. They have a row of black dots along each side, and a row of conspicuous dark half-moons along the back. On some large larvae the half moons and stripes are less distinct.

Final instar larvae are darker and can exceed 50 mm in length. All larvae have four pairs of ventral prolegs, and are more solid than helicoverpa with fewer body hairs.

May be confused with: Small to medium larvae (10 mm) may be confused with helicoverpa and fall armyworm larvae. Differences are the ‘hump’ behind the head and the row of dark spots along each side.

Host range: Adzuki, mungbean, navy bean, peanut, pigeon pea and soybean.

Life cycle: Egg masses are laid on leaves. Young larvae feed on leaves but older larvae may feed on flowers and pods. Larvae pass through six larval stages and take 2–3 weeks to develop, depending on temperature. Larvae pupate in the soil.

Risk period and damage: Crops are most at risk at flowering and podding. Small larvae window leaves, but older larvae chew holes in leaves. Older larvae also attack flowers and pods, but pods are usually only attacked after leaves start to hay off as pods ripen and mature.

Monitoring and control: As for helicoverpa. Look also for egg masses and clusters of young larvae. In pre-flowering crops, control is warranted if defoliation exceeds, or likely to exceed, 33% (see helicoverpa section). Tolerable defoliation drops to 15–20% once flowering and podding commences. NPV does not control cluster caterpillars and they can’t be controlled with Bt unless they are very small. Most pesticides targeting helicoverpa will give good control of cluster caterpillar.

Natural enemies: As for helicoverpa and loopers.

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Fall armyworm, Spodoptera frugiperda  

Lepidoptera: Noctuidae.

Common/other names: Fall armyworm or FAW.

Distribution: The Americas, Africa, Europe, Asia and recently Australia. Larvae present in all states except South Australia and Tasmania. More active in the tropics and coastal regions where warmer temperatures allow it to breed all year long.

Pest status: Soybean is not a preferred host but larvae will move into and feed on soybean if self-sets of their primary hosts (maize/sorghum on which FAW eggs were laid) are sprayed out with herbicides. Soybean crops are also at risk when FAW-hosting weeds (e.g. nutgrass) are sprayed out just prior to planting the crop. Seedling crops are at particular risk because once the canopy is denuded, FAW larvae burrow underground for shelter and destroy the plant’s taproots, killing the plants.

Identification: The moths are similar to but slightly smaller than cluster caterpillar (Spodoptera litura) moths. Male FAW moths have grey/brown forewings with a similar pattern to S. litura but lack the distinctive criss-cross cream streaks of S. litura. Female moths lack any distinctive patterns.

FAW eggs are laid in a furry cream mass on the underside of leaves. Young larvae ‘cluster’ together and are translucent green with a darker head. Mid to large larvae have an inverted white Y making on their heads. Large larvae often have a greasy appearance. All larval stages have four pairs of ventral prolegs.

For more detailed information and identification guides: https://thebeatsheet.com.au/key-pests/fall-armyworm/faw-identification/ and https://thebeatsheet.com.au/wp-content/uploads/2020/06/Armyworm-larvae-May20.pdf 

May be confused with: Medium-large larvae may be confused with helicoverpa larvae, but can be distinguished by the parallel dorsal while lines on the first body segment, as opposed to white scribbles on helicoverpa.

Life cycle: Egg masses are laid on leaves. Young larvae feed on leaves but older larvae may feed on flowers and pods. Larvae take 2–3 weeks to develop, depending on temperature. Larvae pupate in the soil.

Host range: Pulse hosts include mungbean, adzuki, navy bean, peanut, pigeon pea and soybean, but none of these are preferred hosts.

Risk period: Seedlings, vegetative, flowering and podding.

Damage: Small larvae leave transparent windows in leaves, but older larvae chew right through. Older larvae will attack flowers and pods. Their damage potential in soybean crops is not yet measured but may be similar to helicoverpa, except in seedling crops where FAW’s damage potential may be greater.

Sampling and monitoring: As for helicoverpa. Look also for egg masses and clusters of young larvae.

Thresholds: In pre-flowering crops, control is warranted if defoliation exceeds, or is likely to exceed, 33%. However, tolerable defoliation drops to 15–20% once flowering and podding commences. In summer pulses, the provisional threshold post flowering is 3 larvae/m².

Chemical control: Altacor, Affirm and Success Neo (all under permit) should give good control of FAW, and Fawligen (a FAW virus) has potential, albeit only against 1st and 2nd instar larvae. The proviso is that that ‘best practice’ spray protocols are used with spray volumes at least 100 L/ha (preferably higher). Methomyl and SP insecticides are ineffective because of FAW’s resistance to these products.

Cultural control: Spray out FAW-infested weeds well before planting and spray out self-set maize before it is infested with FAW.

Natural enemies: Coetesia sp. wasp parasites and predatory carab beetle larvae have been observed in some FAW infested crops.

Bean podborer, Maruca vitrata (previously M. testulalis)

Distribution: A cosmopolitan tropical pest that is most abundant in tropical and subtropical Australia, particularly in coastal regions. Most abundant in wetter summers.

Pest status and damage: Usually not a pest in soybean crops, but one instance of tunnelling in stems has been reported in soybean crops in coastal Queensland near Bundaberg.

Identification: Bean podborer moths have a 20–25 mm wingspan and a slender body. They have brown forewings with a white band extending two-thirds down the wing from the leading edge. Inside this band near the leading edge is a white spot. The hindwings are predominantly a translucent white with an irregular brown border. When at rest, they adopt a characteristic pose with outspread wings and the front of the body raised up. Larvae are pale cream with two rows of distinctive paired black markings on their back.

Do not confuse moths with those of the beet webworm, which have mostly brown hindwings and fold their wings when back when at rest. Larvae of this species mainly feed on black pigweed.

Host range: Favoured hosts include adzuki, mungbean, cowpea, pigeon peas but not soybean.

Life cycle and damage: In favoured hosts, larvae feed initially in buds and flowers before moving to the pods. Soybean plants are not a favoured host because of their small flowers and (in most regions) their determinacy – the non-overlapping of the flowering and podding stages. The only reported podborer damage to date has been tunnelling in the stems of coastal soybean crops in the Bundaberg region. After completing their development (10–15 days from egg hatch), larvae exit pods and pupate in the soil. Bean podborers are more abundant in wetter summers.

Monitoring and control: Look for tunnelling and associated larval frass in soybean stems. Double check the identity of the caterpillars tunnelling in the stem, as etiella sometimes (infrequently) also tunnel in stems. No thresholds are set as this pest is not regarded as a problem in soybean crops. Report any unusually heavy podborer infestations in soybean crops to DAF entomology on 13 25 23.

Etiella (lucerne seed web moth), Etiella behrii

Distribution: Throughout Australia and much of SE Asia and Pacific Islands.

Pest status: Etiella is an important pest of peanuts and lentils but is a spasmodic pest in soybean crops. However, in the summer of 2014/15, populations of 20 larva/m² or more were widely reported in pod ripening soybean crops, from CQ to northern NSW. However, in more recent summers, etiella activity has mostly reverted to normal non-economic levels.

Host range: Etiella infest many pulses including peanut, mungbean, adzuki, lima bean, lentil and soybean crops. Rattle pods are favoured weed hosts and lucerne can also be attacked.

Identification: Moths are small (12 mm long at rest, 20–22 mm wingspan) and uniquely coloured. They are grey-brown in colour with a distinctive white stripe along the leading edge of each forewing, and an orange band across each forewing. Moths fold their wings back along the body when resting and have a prominent ‘snout’.

The eggs are small (0.6 mm diameter), cream and flattened. Small larvae are cream or pale green, lack stripes, and have a dark head. Mid-sized larvae are pale green or cream, with pale brown or reddish stripes. Larger larvae are characteristically green with pink or reddish stripes and a brown head. Larvae in the pre-pupal stage can be aqua blue or dark pink with no stripes.

May be confused with: Moths can be confused with non-pest Etiella spp. that feed on rattle pods.

Life cycle: Eggs are laid on pods and flowers and terminals and are very hard to detect. In younger plants, newly-hatched larvae tunnel into the terminals and move down the petioles to the stems. This type of damage can kill terminal leaves. In more advanced plants, larvae bore into pods leaving a near-invisible (0.2 mm) entry hole. When larvae reach the pre-pupal stage, they make a much larger exit hole (2–3 mm) and leave the pods to pupate in the soil. The life cycle can be completed in four weeks at 30°C.

Damage: Larval tunnelling in terminals and upper stems can kill leaves and will discolour the pith. Pod samples from commercial crops at pod fill show an etiella larvae consumes only one soybean seed, equating to a yield loss of 2 kg/ha per larva/m² in a soybean cultivar with a MSW = 20 g per 100 seeds. In contrast, the yield loss for a much larger caterpillar pest, helicoverpa, is 40 kg/ha per larva/m². Therefore 20 etiella larvae would be required to inflict as much damage as one helicoverpa larva. The damage described so far results in yield loss. However, if larvae inside pods have not completed their development before the crop is harvested, then a sizable proportion of damaged seeds will only be partially damaged, and thus less likely to be lost at harvest (less likely that a nearly totally eaten seed). The net result is that partially damaged seeds in the harvested product will reduce seed quality. Given that most Australian soybean crops are now grown for human consumption, reduced seed quality due to etiella is an issue that requires further research.

Risk period: Crops are at greatest risk during late pod fill and the pest is more abundant in wetter summers.

Monitoring: Use a sweep net to sample for the distinctive moths with a white streak on the front of the forewings, wings folded back along the body, and snout shaped head. Cut open stems and terminals to look for larval tunnels, and to find any of the distinctive pink-striped green larvae. Similarly, open pods to check for larvae. Note that exit holes in pods indicate the larvae have left to pupate in the soil. However, there should also be tell-tale signs of their recent presence, notably pale frass (poo) and the remnants of damaged seeds.

Control: No pesticides are currently registered or under permit for etiella in soybean crops. Experience in previous outbreaks indicates chlorantranliprole based products may have activity against larvae in terminals. However, subsequent DAF trials showed chlorantranliprole (e.g. Vantacor) has no impact on larvae inside pods.

Risk period and damage: Crops may be infested from flowering onwards, but are at greatest risk during late podding.

Thresholds: Currently there are no validated thresholds for etiella in soybean crops. During the vegetative stage, damage to 25% terminals is the nominal threshold. During pod fill, decision making is complicated by two factors: 1. in some instances, infested crops close to harvest may have a sizeable number of partially damaged seeds likely to be retained at harvest, and thus impact on seed quality; 2. DAF trials show that even Group 28 insecticides such as chlorantranliprole do not reach larvae inside pods.

So, assuming a scenario where 75% of damaged seeds are retained at harvest, the quality threshold for a 2.5 t/ha crop with a 100 MSW of 20 g would be 33 larvae/m², i.e. that is how many larvae would be required to damage 2% of seeds, the critical damage level set for soybean crops, above which penalties can exceed $100/t.

However, if etiella thresholds were based only on yield loss at a rate of 2 kg/ha per larva/m², (only one-twentieth of that for helicoverpa), then for a crop value of $700/t, and a cost of control plus application of $55/ha, the etiella threshold would be 39 larva/m².

As mentioned previously, DAF trials show that insecticides don’t contact larvae feeding inside pods, so in reality, the thresholds are academic. Even if a low 50% control was achieved, the net impact would be to double the threshold. Pragmatically, thresholds in the 30–40 etiella larva/m² range exceed etiella populations reported (sporadically) in most infested crops. Therefore, the impact of high etiella populations in soybean crops is not as great as one might first think. Because of this pest’s sporadic occurrence, it should rank as a minor pest.

While only a minor pest on average, large infestations are of considerable interest to entomologists so please report them to DAF entomology on 13 25 23.

Loopers (green and brown)

The following applies most of the time equally to green and brown loopers.

Pest status: Mostly minor pests feeding mainly on leaves. However high looper populations can inflict economically-damaging levels of defoliation.

Risk period and damage: Loopers can attack crops at any stage but are greatest risk during flowering and podding. Soybean plants are least tolerant of defoliation at these stages. Looper leaf damage is different to helicoverpa damage, the feeding holes being more angular rather than rounded. Loopers rarely attack soybean flowers and pods.

Monitoring and thresholds: Use a beat sheet to check crops twice-weekly during the vegetative, flowering and podding stage until crops are no longer susceptible to attack. In pre-flowering crops, looper control is warranted if defoliation exceeds, or is likely to exceed, 33%. Tolerable defoliation drops to 15–20% once flowering and podding commences.

Control: All insecticides targeting helicoverpa, except helicoverpa NPV, will be effective against loopers. Bt (e.g. Dipel) will control up to medium size green loopers (15–20 mm long), but brown loopers are harder to kill. For chemical control options refer to the APVMA website. https://apvma.gov.au/node/10831

Natural enemies: Loopers are frequently parasitised by braconids (Apantales sp.) with scores of parasite larva developing per looper host. Predatory bugs, tachinid flies and ichneumonid wasps also attack loopers. The use of Bt (Dipel) will help preserve beneficial insects. Outbreaks of looper NPV are frequently observed in crops with high looper populations. However, larvae are usually not killed by the virus until they are medium-large (instars 4 or 5). Looper NPV is not the same as helicoverpa NPV and the latter has no impact on loopers. 

Green loopers

• Soybean looper, Thysanoplusia orichalcea

• Tobacco looper, Chrysodeixis argentifera

• Vegetable looper, Chrysodeixis eriosoma

Distribution: Green loopers occur in all soybean growing regions

Identification: The soybean looper moth has distinctive brown forewings with a large bright golden patch. The tobacco and vegetable looper moths have dark brown forewings with small silver ‘figure eight’ markings. All species have a 40 mm wingspan. Looper eggs are a pale yellow-green and are flatter than helicoverpa eggs. Larva move with a distinctive looping action and have only two pairs of ventral prolegs. Green loopers taper noticeably towards the head. Larvae are mostly green with white stripes, though colours can vary. Soybean loopers are more prominently striped, particularly when medium sized, when they often have dark stripes and can be confused with helicoverpa larvae. Larvae can reach 45 mm in length. Unlike helicoverpa, which pupate in the soil, loopers usually pupate on the plant under leaves in a thin silken cocoon. Pupae are dark on top and pale underneath.

Brown loopers

• Bean looper or Mocis, Mocis alterna

• Sugar cane looper, Mocis frugalaris

• Three barred moth, Mocis trifasciata

• Pantydia sp., (no common name)

Distribution: Mocis sp. loopers occur in Africa, Asia and Australia. The bean looper is native to Australia. Brown loopers are most common in tropical and subtropical coastal soybean growing regions.

Identification: Moths have 30–50 mm wingspan, Mocis trifasciata being the largest species. Sugar cane looper moths are brown and have a diagonal dark line with a pale inner edge across each forewing. The other loopers are grey or brown with dark bands and markings on all wings. Eggs are globular and pale green and are larger than helicoverpa eggs.

Larvae vary in colour and can be cream, charcoal, bright orange or brown. The bean looper varies most in colour and larvae may have dark stripes along their back and often have a cream or yellow band along each side. Larvae can reach 40–50 mm in length with Mocis trifasciata the largest species. Larvae have two or three pairs of ventral prolegs, move with a looping action, and are more slender than helicoverpa, particularly in the younger stages. A distinctive feature of Mocis larvae is their forward sloping and striped heads. Larvae pupate inside curled leaves.

Common grass blue (butterfly), Zizina labradus

Lepidoptera: Lycaenidae 

Also known as grass blue and lucerne blue.

Distribution: Native to and spread throughout Australia including Tasmania.

Pest status: Mostly minor but frequently causes significant damage to soybean crops in NSW and Qld. Quite common in the Bundaberg region.

Identification: The adult’s wings are pale dull blue on top with dark grey edgings (wider in the females). They lack tails and eye spots. The undersides of the wings are brown with soft markings. The eggs are relatively large (1 mm diameter), bluish and flattened with a central depression, and are laid singly. The small green slug-like larvae reach only 10 mm in length. Larvae are pale green with a central pale stripe and often with pale patterning on their back. Their head is difficult to see as it is usually tucked out of sight.

May be confused with: Larvae are sometimes confused with hoverfly (Diptera: Syrphidae) larvae, which are also ‘slug-like’, are of similar size, and may be similarly coloured and patterned. Both may also be found on leaf terminals. However, hoverfly larvae are more tapered towards the head, often wave the front of their body from side-to-side, and are aphid predators. Other lycaenid larvae are also similar in outline and colour, particularly those of the bean flower caterpillar, Jamides phaseli. The adults can be distinguished from other lycaenids such as the pea blue, Lampides boeticus, by their lack of eyespots and tails.

Host range: Feed on most pulse legumes but most common in soybean crops. They also feed on lucerne.

Life cycle: Eggs are laid singly on leaves. Larvae mostly feed on leaves. Larvae pupate in loose webbing under leaves.

Risk period: Can attack at any stage. Less vigorous drought-stressed plants are at greatest risk as terminals are more likely to be attacked. Young crops are often attacked.

Damage: Larvae feed mostly on leaves and terminals, but occasionally feed on flowers. Damaged leaves may be windowed. Excessive terminal loss results in pods being set too close to the ground, which makes harvesting difficult.

Monitoring: Check crops with a beat sheet, look for larvae inside terminals, and for large numbers of the distinctive (and pretty) blue butterflies.

Action level: Control if terminal loss exceeds 25%.

Control: Most products targeting helicoverpa (except Helicoverpa virus) will also control this pest. Bt (Dipel) also gives good control and is an IPM-friendly soft option. In 2019, a minor use permit (PER87644 – now expired) was secured for chlorantraniliprole (Altacor) to control an extremely high outbreak (12 larvae per square metre) in the Maryborough district, causing major damage, with many plants incurring damage to terminals, buds and flowers.

Leaf miners and webbers

• Soybean moth Aproaerema simplexella 

• Legume webspinner or bean leafroller Omiodes diemenalis 

Soybean moth, Aproaerema simplexella 

(previously Stomopteryx simplexella) 

Pest status: Mostly minor. Soybean moth is common in soybean crops but is usually only present in low numbers with only the occasional leaf slightly webbed and folded to provide a shelter for larvae. However, they spasmodically occur in very high numbers, inflicting significant leaf damage, and on rare occasions can destroy crops by denuding all the plants.

Identification: Moths are small (6 mm long) with narrow dark wings with a transverse white band. Caterpillars are small (up to 7 mm long) and are grey green with a dark head. Larvae are usually found feeding inside the leaves, i.e. in leaf mines, which are straw coloured. The small eggs are often laid on leaf veins.

Damage and control: Soybean moth larvae initially feed inside (mine) leaves and sometimes emerge to feed externally, folding and webbing leaves together. Larvae normally only cause cosmetic damage but heavy infestations can make multiple leaf mines per leaf, resulting in leaf death.

Infestations are favoured by hot, dry weather, with crops under severe moisture stress most at risk. Crops near trees are often more severely infested.

Monitoring: Scout crops regularly for the early warning signs of severe infestations. Look for numerous small pale patches (leaf mining) on the leaves and swarms of soybean moths around lights at night. Indicative threshold is based on defoliation, i.e. 33% pre-flowering and 15–20% during early pod fill.

Control: Control is rarely required and no specific registrations exist for soybean moth. However, abamectin (registered for use in soybean crops against mites) can be used under PER86185 and gives good control of soybean moth at the mite rate (300 mL/ha). Check that larvae have not reached the pre-pupal stage during which they cease feeding, and are not impacted (killed) by the insecticide. Note also that PER86185 permit expires on the 30 April 2023.

Legume webspinner or bean leafroller, Omiodes diemenalis

(previously Lamprosema abstitalis) 

Pest status: Minor. Widespread in coastal regions but rarely at damaging levels.

Identification: The distinctive moths are brown with bright yellow patches and an 18 mm wingspan. Larvae roll and web leaves together. They are considerably larger than larvae of the soybean moth. Young larvae are pale green with dark heads. Older larvae are shiny green with pale brown/orange heads and reach 15 mm in length.

May be confused with the soybean moth and bean podborer larvae.

Host range: Soybean, mungbean, adzuki and navy bean.

Risk period and damage: Legume webspinners are widespread in coastal regions but rarely at damaging levels. Crops are usually at greatest risk during early podding. The larvae are leaf feeders, webbing leaves together. Silken webs and frass are indicative of webspinner attack, but other leaf webbers cause similar symptoms.

Monitoring and control: Larvae are sometimes detected when beat sheet sampling. Also inspect webbed leaves and look for the characteristic frass. The threshold is based on tolerable defoliation, i.e. 33% pre-flowering and 15–20% during early pod fill. Control is rarely required.

Beetle pests

• Monolepta or redshouldered leaf beetle or Monolepta australis

• Lucerne crown borer (LCB) or Zygrita diva  

Monolepta or redshouldered leaf beetle, Monolepta australis

Distribution: Throughout northern Australia. Particularly abundant in coastal cane-growing regions where larvae feed on sugarcane roots.

Pest status: Monolepta can arrive suddenly in large numbers, inflicting rapid defoliation and flower loss.

Identification: Beetles are 6 mm long and are yellow with a distinctive dark red (purple) band across the shoulders and two red/purple spots on the ends of the wing covers. The flaccid, yellowish eggs are small (< 1 mm across) and oval. Larvae are white, 5 mm in length, slightly flattened with hard brown plates at both end.

Host range: Adults feed on a broad range of plants including soybean, navy bean, mungbean and peanut. Other hosts include avocado, cotton, lychee, macadamia, mango, strawberry, and numerous ornamentals. Larvae feed on roots of sugarcane and pasture grasses.

Life cycle: Eggs are laid in the soil surface, mainly in pastures and sugar cane fields. Larvae feed on the grass roots and pupate in the soil. The life cycle takes about two months in summer and there are three or four generations annually. Adults usually emerge from the soil after heavy rains following a dry spell. If larval populations in the soil are high, the multitude of emerging beetles will form an aggregation and swarms may migrate into nearby soybean crops.

Risk period and damage: Monolepta are common in sugar cane areas. They can arrive suddenly in large numbers, infecting rapid defoliation and flower loss. Soybean crops are at greatest risk during flowering. Infestations are most likely after heavy rainfall events. Monolepta attack leaves and flowers with very high populations (e.g. > 50/m²) shredding leaves and denuding crops of flowers.

Monitoring and thresholds: Monolepta are readily assessed visually or with a beat sheet but can be difficult to count as they are extremely flighty. Estimate the number of groups of 5 or 10 beetles on the sheet to get a ‘ball park’ population estimate. Check crops after heavy rainfall that may trigger the mass emergence of adults. Thresholds are not yet established but populations greater than 20/m² can cause significant damage in flowering crops. Defoliation thresholds are the same as for leaf feeding caterpillars.

Control: Monolepta beetles are readily controlled with Steward® (indoxacarb) at 200 mL/ha. Spot treatment of border rows close to sugar cane may be sufficient. If possible, plant soybeans away from key Monolepta hosts such as sugar cane.

Lucerne crown borer (LCB) or zygrita, Zygrita diva

Lucerne crown borer is often a problem where soybean crops are grown in or near paddocks planted to soybean last summer, in close proximity to lucerne, and in edamame beans.

Identification: Adults are 15 mm long and bright orange with black legs and long black antennae. They usually have two prominent black spots on their wing covers, but these may be absent or more spots can be present. The similar shaped, mottled brown Corrhenes stigmatica (also a stem borer) is less common. Larvae of this species are cream with a wide head and are up to 25 mm in length.

Host range and life cycle: This pest can be found in soybean crops and lucerne as well as in phasey bean and sesbania. Infestations occur when eggs are inserted in the stems of young soybean plants, usually in the early to mid vegetative stages. Larvae tunnel up and down through the pith in the stem and petioles, but usually pupate in the taproot. In cooler seasons, larvae don’t pupate until pods are mature, but in hot summers, larvae may pupate before pods are filled.

Risk factors and damage: Soybean crops in the tropics, or growing in very ‘hot’ summers, or near lucerne are at greatest risk from severe crown borer damage. Proximity to lucerne increases the risk of early infestation. Larval feeding in stems has little impact on yield but prior to pupating in the taproot, plants are internally ringbarked or girdled to seal the pupal chamber causing plant death above the girdle.

In cooler summers in more southern regions, e.g. SEQ, girdling usually occurs after seeds are fully developed (physiological maturity) with little yield loss. In hotter summers and in tropical regions, LCB larval development is more rapid and there can be considerable crop losses if plants are girdled before pods are filled. Plants in thin stands may also lodge before harvest and if not picked up are totally lost.

Crown borers are very damaging to edamame soybean crops where green immature pods are harvested using mechanical pod pluckers, the weakened stems of infested plants being plucked into the harvester as well.

Monitoring: Look for adults when beat sheeting and for the distinctive oviposition scars on the stems and petioles. Break open stems to look for larvae and eaten out and brown discoloured pith. In older plants, look for dead plants, killed when larvae girdle the stems prior to pupation.

Thresholds: Thresholds for LCB in soybean crops are problematic. This is because the most effective insecticide strategies, seed treatments or in-furrow sprays, are applied at planting before the crop is infested, and aim is to reduce subsequent damage inflicted by LCB at pod fill to harvest. In effect, such treatments are prophylactic but to date, are the most effective way to reduce LCB damage. So in effect, the thresholds are retrospective, and are based on the ‘most likely’ level of anticipated damage, i.e. on the LCB history of the paddock. The threshold will also (obviously) be determined by the cost of the control option selected.

Chemical control: Currently there are two APVMA permits for the control of LCB with fipronil, PER88231 and PER88226 for seed treatments and in-furrow sprays at planting respectively (see APVMA website https://apvma.gov.au/node/10831 ). These at-planting applications aim to reduce and delay the early infestation of LCB, thereby delaying the onset of and the severity of girdling later in the season. In DAF trials, seed treatments at the permit rate of 200 mL (50% a.i.) product, the fipronil seed treatment more than halved the percentage of plants infested and the percentage of plants girdled, and doubled the yield. Note that fipronil is being reviewed by the APVMA and its continued availability cannot be guaranteed.

Foliar sprays targeting adult beetles have been shown to be ineffective against LCB and similar species in the USA, but increase the risk of killing beneficials and flaring mites and whitefly.

Prophylactic management decisions are best based on previous LCB history in the paddock and surrounding area and the predicted temperatures for the coming summer (e.g. severe LCB damage is more likely in a hot El Niño summer than in a cooler cloudy La Niña summer).

Because of the nature of LCB infestations, a typical economic threshold is not appropriate, however, a general guide can be calculated. (see graph below). These thresholds are based on a soybean price of $600/t, a plant density of 30 plants per square metre, a fipronil seed treatment formulation costing $790/L and ranging from $71–$142/ha, depending on planting seed size, and an in-furrow formulation costing $50/ha.

The easiest method is to consider past experience with this pest and to keep records of the percentage of plants infested, the relative size of the pods/seeds in girdled plants (what % of pod fill has been achieved), and typical yield loss. This is because the impact of an LCB infestation depends on (i) the percentage of plants infested and (ii) the yield loss per infested plant/larva. Larvae are cannibalistic and normally only one larva per plant survives to overwinter. Yield loss also depends on how early plant girdling commences.

If most of the infested plants have typically been girdled by early pod fill, the yield loss (per larva/m²) could potentially approach 80 kg/ha. But if most infested plants have not been girdled until pods are ≥80% filled, the yield loss is much lower, perhaps 20 kg/ha per larva/m². If the rate of LCB damage in the crop and local area fluctuates widely, it may be best to base a decision on the ‘average’ potential yield losses, say 40 kg per larva/m². 

Note the significant impact seed size has on the seed treatment thresholds, and the much lower thresholds for the in-furrow treatment. Note also how low the thresholds are for high yield loss scenarios (with a yield loss of 80 kg/ha).

Following severe LCB damage, seed treatments will most likely be justified in future crops. But on average, if the typical damage experienced is very low, then seed treatments are probably not justified, particularly for large-seeded cultivars. The lower price of in-furrow sprays may be attractive, even if they are not quite as effective as seed treatments.

Cultural control (non-insecticidal): 

• Avoid planting soybean crops close to lucerne or close to paddocks where soybean crops were planted last season.

• Never plant successive soybean crops in the same paddock without a break between.

• If in an at-risk region (regularly experiencing high LCB damage), consider later plantings to shorten crop development. In the tropics, consider winter plantings.

• Avoid thin plant stands to reduce the lodging of damaged plants.

• Irrigate crops to reduce plant stress where possible, particularly from early pod fill onwards. Moisture stress can trigger premature girdling by LCB.

• Strip till infested soybean stubble to break open and bury infested stubble, thereby killing overwintering LCB inside the stubble.

Remember that non-insecticide management options are not only IPM-friendly, they provide a plan B should fipronil ever be withdrawn by the APVMA due to environmental concerns.

Soybean aphid, Aphis glycines

This exotic pest was detected in Australian soybean crops during the 1999/2000 season. It is more prevalent in crops on the coast than inland and more abundant in cooler summers.

Identification: Soybean aphid is small (to 2 mm long) and has a very bright, translucent green body. This aphid also has black siphunculi and a pale cauda.* No other aphid found on soybean plants has the same size and colour combination.

*Siphunculi (or cornicles or honey tubes) are a pair of upward and backwardly pointing tubes on the top of an aphid’s back/abdomen. The cauda is a ‘tail-like’ structure, usually present below and between the siphunculi on the last abdominal segment.

Damage: Aphids are normally not a major threat to soybean crops, but populations should be monitored. In the unusually cool summer of 2007/08 severe aphid outbreaks occurred in the Bundaberg region. Aphids are more prevalent on the coast than inland. Cast off (white) aphid skins are evidence of past infestations. Heavily infested plants may be covered in sooty mould growing on honeydew secreted by the aphids. Such infestations can reduce yield significantly and delay harvest maturity. Heavily infested plants often have distorted leaves. Crops become less attractive to aphids after early podding. The adult, winged-form of the aphid, is able to travel long distances on prevailing wind currents.

Monitoring: Look for aphids on the upper stems, leaflets and terminal leaves. In heavily infested crops, cast off aphid skins, sooty mould and large ladybird populations are indicative of soybean aphids. However, the latter two can also indicate significant whitefly activity.

Thresholds: In the USA, the soybean aphid threshold is set at 250 aphids per plant from budding to podding. As a rule of thumb, once soybean aphids are present on the main stem, populations are in excess of 400 aphids per plant.

Chemical control: Options for above-threshold aphid populations include pirimicarb (PER85152), and sulfoxaflor (Transform) and dimethoate (both registered). Of these, dimethoate at the registerd rate of 800 mL/ha is the hardest (so consider using a lower rate), and pirimicard is the softest with least impact on beneficials. Transform is moderately selective.

Biological control: In most seasons, natural enemies, especially ladybirds and hoverfly larvae kepp aphids in check. During the vegetative stage, avoid ‘hard’ non-selective pesticides against other pests, as these pesticides may kill beneficials and ‘flare’ the aphids.

Mirids

Hemiptera: Miridae

• Green mirid, Creontiades dilutus

• Brown mirid, Creontiades pacificus

Distribution: The green mirid is widespread and endemic to Australia but the brown mirid also extends into Asia.

Pest status: Mirids are only a minor to moderate pest of soybean crops. This contrasts with their major pest status in mungbeans.

Identification: Mirid adults are 6–7 mm long with elongated bodies, long legs (especially the hind legs) and long antennae. Green mirid adults are pale green and sometimes have reddish flecking on their legs. Adult brown mirids have two distinct colour forms. The brown form is predominantly light brown with darker pigmentation on their hind legs, and the green form is mostly bright green with dark red (purple-brown) pigmentation of the head, hindlegs and parts of the thorax.

Mirid nymphs are smaller, elliptical-shaped and lack wings. Young nymphs have antennae much longer than their body. First instar nymphs are pale brown/orange but later instars are pale green. Green mirid nymphs have pale antennae while brown mirid nymphs have distinctive reddish (brown) antennae with white banding.

Hosts: Mirids attack a wide range of summer legumes including adzuki, mungbean, navy bean, peanut, pigeon pea and soybean. Other hosts include cotton, horticultural crops and lucerne.

Life cycle: Mirids may be present at any stage from seedlings to podding. Populations are often low during the vegetative phase but increase rapidly after budding. Over 80% of mirids in flowering legumes may be nymphs and populations in excess of 5/m² are not uncommon. Populations frequently decline once flowering ceases. Pale, elongated eggs are laid singly into plant tissue with a small area of the egg exposed. There are usually five nymphal stages. Mirid development from egg to adult is very rapid at high temperatures and takes only 16 days at 30°C. Egg development is relatively slow and makes up 37% of total development time.

Risk period: Soybean crops are potentially at greatest risk during budding, flowering and early podding. However, soybean are at far less risk of economic damage than susceptible hosts such as mungbean. Low mirid populations are often present in vegetative soybean crops but there is no evidence they cause ‘tipping’ of vegetative terminals as occurs in cotton. Influxes of mirid adults often follow northwest winds in spring.

Damage: Mirids attack buds, flowers and small pods. However, soybean crops are less susceptible to mirids than mungbeans. Mirid populations of up to 5/m² had no impact on soybean yield in DAF trials. For this reason, mirid thresholds in soybean crops are far higher than in mungbeans.

Monitoring: Mirids are very mobile pests and in-crop populations can increase rapidly. Inspect crops twice-weekly from budding onwards until post flowering. The preferred monitoring method is the beat sheet. Sample five one-metre lengths of row (not consecutive) within a 20 m radius, from at least six sites throughout a crop. Avoid sampling during very windy weather as mirids are easily blown off the beat sheet.

Thresholds: The mirid thresholds for soybean is 5 or 6 mirids/m².

Chemical control: Dimethoate is registered at 500 mL/ha (all summer pulses). Dimethoate is often applied at lower than label rates (e.g. 250 mL/ha), with the addition of a 0.5% salt adjuvant. This half rate gives excellent mirid control but has far less impact on most beneficials. The rate of salt used (0.5% w:v) has no phytotoxic effect on soybean.

Indoxacarb (Steward) is also registered at 400 mL/ha but gives very poor mirid control.

‘Hard’ water can markedly lower the effectiveness of dimethoate and should be countered by adding a buffering agent such as Li700.

Leafhoppers vectoring phytoplasma

Common brown leafhopper, Orosius orientalis

Hemiptera: Cicadellidae 

The period 2013 to 2017 saw an increased incidence of a leafhopper-vectored phytoplasma disease in soybean and other pulses in Eastern Australia. While the disease incidence has declined on average in more recent years, there is no guarantee it won’t return.

Phytoplasmas are specialised bacterial diseases and are vectored by phloem-feeding insects. The vector is the common brown leafhopper Orosius orientalis and the specific phytoplasma is pigeon pea little leaf phytoplasma (PPLL) (Candidatus Phytoplasma aurantifolia 16SrII-B).

All regions from the Burdekin to central NSW have reported outbreaks of varying severity. One of the worst was in 2016 on a Darling Downs property where a 300 ha soybean crop was destroyed because 100% of the plants were infected and failed to set any viable pods.

Identification: Brown leafhoppers are 3 mm long and pale brown with a speckled pattern of darker lines on their wings and body. They have wide rounded heads and short antennae.

Other leafhoppers often reported in large numbers in soybean crops include the bright green vegetable jassid (Austroasca viridigrisea). This species causes stippling on the leaves (tiny white feeding spots) but is not a phloem feeder nor a transmitter of phytoplasma. Images and additional information about leafhoppers, including the common brown leafhopper https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/biosecurity/plants/insects/field-crop/leafhoppers 

Phytoplasma symptoms: Phytoplasma severely disrupts the crop’s reproductive capacity, resulting in small, deformed flowers and pods that do not produce harvestable pods and seeds. If plants are infected at a very early stage (i.e. as seedlings), they may produce no flowers at all – only masses of tiny leaves (little leaf). Note that damage symptoms may not manifest until 2 to 3 weeks after plants are infected. Images of phytoplasma symptoms in various crops, including soybean https://thebeatsheet.com.au/disease/image-by-disease/phytoplasma/ 

Sampling and monitoring: Leafhoppers are most easily sampled with a sweep net. A sample of 20 sweeps over two rows is recommended, with the net everted into a large glass jar to enable the observer to closely inspect the catch.

Chemical control: Dimethoate is registered for jassid/leafhopper control in soybean crops, but at the very high (IPM disruptive) rate of 0.8 L/ha. Recent DAF trials with other leafhopper species (not Orosius sp.) show good control can be achieved at rates as low as 250 mL/ha (+ 0.5% w:v salt adjuvant), a rate that is far less disruptive to beneficial insects. However, at this stage it is unclear at how effective insecticide sprays are in preventing phytoplasma outbreaks, or whether different strategies (e.g. seed treatments) would be effective.

Cultural control: Remove any potential phytoplasma hosting weeds from your property as they are often the source of phytoplasma carried into crops by the leafhoppers. Weed species hosting phytoplasma include rattle pods, milk thistle, bell vine and peach vine.

Rutherglen bug (RGB), Nysius vinitor

Hemiptera: Lygaeidae

Distribution: Native to Australia.

Pest status: Sporadic pest. Mostly in very low numbers in soybean crops in most years but can reach incredibly high numbers in favourable years.

Identification: Adults are 3–4 mm long, mottled grey-brown-black and have clear wings folded flat over their back. Nymphs are wingless with a reddish-brown body. Images and additional information about RGB https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/biosecurity/plants/insects/field-crop/rutherglen-bug 

May be confused with: Adults may be confused with the grey cluster bug (Nysius clevelandensis), which are slightly larger and of similar colour. These can be distinguished from RGB with a hand lens with the grey cluster bug being hairy and RGB having a smooth appearance.

Life cycle: RGB have eight generations a year. In spring and summer, development from egg to adult takes 3–4 weeks. Adults will live up to four weeks, and females will lay up to 400 eggs in this period. Populations of RGB in cropping areas will breed on weeds, moving to available crops or weeds when hosts die off. Adults will overwinter, then move to available weeds and crops in spring and start to breed. In seasons when RGB is a major pest, the population is dominated by migrants, which are carried from inland breeding sites to eastern cropping regions.

Damage: RGB can remove all flowers, cause reduced yield during all pod fill stages and affect seed quality in late pod fill. Damaged seeds have many very fine dark sting marks.

Sampling and monitoring: With a beat sheet. RGB tend to cluster in dense clumps and often very patchily distributed with hundreds on some plants and very few on others.

Thresholds: Unknown. Check the Beatsheet Blog regularly for any updates. https://thebeatsheet.com.au

Chemical control: The insecticide Skope (acetamiprid + emamectin) has been recently registered for RGB control in soybean crops. DAF trials have shown that half rate dimethoate (250 mL/ha) with 0.5% w:v salt to be as effective as the full 500 mL/ha dimethoate rate, and may provide residual activity for up to one week. However, when present in plague numbers, RGB can quickly reinfest crops within hours or days.

Cultural control: Consider neighbouring crops and weeds, particularly sorghum, sunflower and canola. Control potential weed hosts before the soybean crop is planted. Controlling weeds post planting may only shift the pest to your crop.

Natural enemies: Unknown.

Soybean stemfly, Melanagromyza sojae

Diptera: Agromyzidae

Distribution: Widely reported from the Burdekin to the Northern Rivers of NSW.

Pest status: Stemfly pest status is yet to be fully determined. Major outbreaks are spasmodic and the pest’s impact on crops are often confounded by similar symptoms caused by diseases such as Target spot, Anthracnose and Charcoal rot. Heavily stemfly-infested crops in the Casino region in 2017 exhibited no plant death symptoms, and conversely, no stemfly larvae or damage were detected in other crops heavily infested with charcoal rot.

Identification: Adults are small (2 mm long) and shiny black with clear wings. The legless larvae (maggots) are cream with dark mouthparts and reach 3 mm in length. Pupae are small, brown and cylindrical with rounded ends. 

May be confused with: Stemfly adults look very similar to beanfly adults (Ophiomyia phaseoli). Stemfly larvae are easily distinguished by their shrunken atrophied posterior spiracles, as opposed to the trumpet like ones of beanfly. Larval tunnels in the stem may also be confused with tunnels made by lucerne crown borer larvae, but the latter make bigger tunnels, are larger, and have a distinct head capsule.

Life cycle: Eggs are laid in young leaves and the larvae make their way to the stem where they tunnel in the pith. After 8–11 days, larvae are ready to pupate, but before doing so, make an exit hole from which the adult can leave the stem. This hole damages the stem’s xylem and phloem (vascular) tissue and may affect the plant’s growth and reduce yield. The pupal stage takes 6–12 days (depending on temperature).

Host range and risk period: Soybean. Younger plants are at greater risk, but infestations often peak during flowering and early pod fill.

Damage: Infected stems are often red inside (sometimes pale) and a distinct zig-zag tunnel may be observed with maggots or pupae inside. Apart from the exit holes, the soybean plants will initially appear healthy on the outside. Large infestations (3 or more maggots per plant) may cause wilting and may even cause plant death, especially in younger plants. In many instances, diseases such as charcoal rot cause similar symptoms.

Sampling and monitoring: Adults are best sampled with a sweep net. Larvae are best sampled by cutting stems open. Also look for parasites in the sweep net.

Chemical control: Emergency use PER14120 for dimethoate @ 800 mL/ha has long expired but could be renewed if there are future major stemfly outbreaks. In the longer term, alternatives to dimethoate may be required.

Thresholds: No official thresholds. Only spray if stemfly are present in ‘reasonable’ numbers (numerous larvae per plant) and there are unhealthy plant symptoms that are NOT disease related. Note that diseases such as Charcoal rot and Phomopsis are manifested by poor root development, distinctive stem discolouration and leaf discolouration and death, and eventual plant death.

If it is necessary to spray, target the larvae before they reach the stems. Once inside the stems, larvae cannot be controlled as they are feeding on non-vascular tissue. Note that the Casino crops sprayed with the beanfly rate of dimethoate (800 mL/ha) in 2013 experienced an explosion of white fly numbers, from already very high levels.

Natural enemies: Stemfly larvae are often parasitised by small metallic coloured Chalcidoid wasps, populations of which build up as the season progresses.

Liriomyza sp. leafminers (Diptera: Agromyzidae) – recent exotic incursions

• Serpentine or pea leafminer (SLM) Liriomyza huidobrensis

• Vegetable leafminer (VLM) Liriomyza sativae

• American serpentine leafminer (ASLM) Liriomyza trifolii

Distribution: SLM has been recorded in Southern Qld in the Fassifern and Lockyer Valleys, the Darling Downs and the Granite Belt, as well as in NSW, and is spreading. VLM and ASLM have been reported on Cape York, and the latter (ASLM), also in the NT and northern WA.

Pest status: Potentially significant if populations increase in the main pulse regions. ASLM may be the most damaging species for pulse crops.

Identification: Adults of all three species are small (≈1.5 mm) black and yellow flies. Both SLM and VLM have shiny black thorax, but SLM has a dark femur (leg segment) while VLM has yellow femur. ASLM also has yellow femur but a matt black thorax. Eggs are about 2 mm long, pale white and laid into the leaf. Larvae are initially translucent but mature to be pale green then yellow (up to 2.3 mm long). SLM larvae mainly feed in leaf mines on the underside of leaves while VLM and ASLM feed mainly in mines on the upper side of leaves. Pupae are orange or reddish brown and 1.5 mm long.

May be confused with: Beanfly and soybean stemfly adults, which are mostly black. Larvae of these two species do not tunnel under the leaf surface like Liriomyza sp. leafminers. In 2019, a native Agromyzid leaf miner was detected in a late summer mungbean crop at Emerald CQ. However, larvae of this native species Tropicomyia sp. produce blister like leaf mines, not the elongated tunnels of Liriomyza sp. leafminers.

Life cycle: Female flies can lay up to 300–400 eggs. Mature larvae tunnel under the leaf surface before exiting the leaf and pupating in the soil. One life cycle takes only two weeks in warm weather, with 2 days for eggs, 5 days for larvae, and 7 days for pupation.

Host range: Most pulse crops including mungbeans, pasture legumes including siratro, as well as brassicas, cotton, lucerne, onion, potatoes, tomatoes and a large number of weeds species.

Risk period: Young crops are at greatest risk.

Damage: Primarily leaf miners but can also damage petioles and soft pods. Leaf mining produces distinctive pale tunnels, which wind irregularly through the leaf and increasing in width as larvae mature. SLM larvae mainly feed in leaf mines on the underside of leaves, often along leaf midribs. In contrast, VLM and ASLM feed mainly in mines on the upper side of leaves. Severe damage may result in leaf death, affecting the plant’s ability to photosynthesise and resulting in reduced plant growth and yield.

Sampling and monitoring: Leaf mining is usually the first and most obvious symptom. Any suspect mining should be reported first and then sent in well-sealed packages for identification.

Thresholds: Unknown. As a rule of thumb, no yield is lost if defoliation remains below 33% in vegetative crops and 16% in pod filling crops. However, if the cost of control and impacts on beneficial insects are factored in, the tolerable defoliation could be as high as 40% and 20% respectively.

Chemical control: No chemicals are currently registered but there is a permit (PER89184) for dimethoate at up to 800 mL/ha in pulses.

Cultural control: Avoid successive plantings of leafminer hosts. Control potential weed vectors.

Natural enemies: Small wasp parasites of beanfly may also attack these leafminer pests.

Two-spotted or red spider mite Tetranychus sp. 

Pest status: Two spotted or red spider mites (the same species) can cause severe damage, particularly during hot, dry weather, but are not a problem in most crops. Mite outbreaks are often the result of ‘hard’ pesticide sprays (targeting other pests) that kill the mites’ natural enemies.

Identification: Adult mites are 0.5 mm long, have eight legs, and in summer are usually yellow-green with large dark green spots on each side of the body. The overwintering form is red with dark spots. Nymphs are similar but smaller in size.

Feeding behaviour and damage: Mites initially invade the lower leaves and gradually move to the top of the plant as populations build up. They make fine webbing on the underside of the leaves, and feed using a rasping and sucking action. Infested leaves take on a speckled appearance. In severe cases, the damaged leaves turn yellow-brown before they wither and drop from the plant.

Heavy infestations during flowering and early pod formation result in early leaf senescence and may significantly reduce seed size and yield. Heavy mite infestations during pod fill hastens leaf drop and brings on early senescence. Yield loss from mites can be as high as 30%, with the late maturing, longer season varieties most as risk.

Control: Abamectin currently gives effective control. The threshold is 30% leaves infested. While still registered, dimethoate no longer provides effective control as mites are now resistant to older miticides. As mites have the potential to also develop abamectin resistance, every effort should be made to avoid flaring mites with non-selective insecticides.

Field crickets

• Black field cricket, Teleogryllus commodus

• Brown or inland field cricket, Lepidogryllus parvulus

Pest status: Spasmodic pests capable of inflicting serious pod damage that looks like mouse damage.

Identification: Both are typically cricket shaped, with long powerful jumping hind legs, large jaws and long antennae. The black field cricket is larger (30 mm) and darker than the brown field cricket.

Behaviour and damage: Field crickets shelter in cracks in the soil and can cause serious losses in soybean crops, particularly in areas with heavy cracking soils. Field crickets often attack seedlings but late summer infestations chew holes in pods to eat the developing seeds. Plagues are most common when mild winters are followed by warm, dry summers.

Monitoring: Check crops for crickets at dusk or at night when they are most active. Cricket activity can also be monitored with light traps. Alternatively, place hessian bags overnight at regular intervals across the paddock. In the morning check for crickets sheltering under bags.

The best way to determine whether mice (and not crickets) are the culprits is to check crops at night or to use mouse bait cards (https://www.daf.qld.gov.au/__data/assets/pdf_file/0003/74262/MouseHouse-BaitCard.pdf). If little mounds of damaged pods are found on the ground throughout the crop, then mice are the most likely culprits, as this is classic rodent food-hoarding behaviour.

Control: Grain baits are recommended for in-crop control of crickets under permit (PER8522). Use a mix of 100 mL Lorsban (50% a.i.) with 125 mL sunflower oil per 2.5 kg cracked wheat. Combine the Lorsban and oil before adding the grain then let the mix ‘set’ for 6 to 8 hours before spreading 2.5 kg of the bait mix per hectare. Use sorghum if cracked wheat is not available. Ideally the grain should be cracked into small pieces, but not ground to fines. Some aerial applicators will supply a similar bait mix. Note that control with baits is difficult in soybean crops with dense canopies.

Black field earwig, Nala lividipes

Pest status and identification: Periodically cause serious damage to seedling crops. Black field earwig are most prevalent in areas with cracking soils. They are elongated, 15 mm long, with short wing covers and large pincers at their rear. Do not confuse BFE with the much larger (20 mm) light brown predatory earwig.

Damage and control: These soil-dwelling insects feed on the germinating shoots. and on recently emerged seedlings which they ringbark at ground level. In-crop treatments with chlorpyrifos grain baits can provide a degree of control.

Slugs 

Pest status: Increasing in zero-till crops in wetter seasons. The wet spring early summer conditions of 2010/11 favoured the return of slugs not seen for many years. Damaging slug populations, reported in seedling crops in northern NSW and southern Queensland, have totally destroyed some crops. Later slug infestations have attacked soybean pods.

Risk factors: Increased zero/minimum till and stubble retention practices that favour slug and snail development and survival. Increased organic matter provides an increased food source, especially to young slugs (and snails). Other high slug risk factors include prolonged wet weather, trash blankets, weedy fallows and a previous slug history. Slugs are best controlled before the crop is planted.

Monitoring: Determine the slug risk in the paddocks prior to planting. Monitor regularly so slug numbers can be detected early prior to planting, as there are more control options at this time. To estimate slug numbers, place wet carpet squares, hessian sacks or tiles on the soil surface. They should at least be 32 cm x 32 cm (10% of a square metre). Place slug pellets under them and check after a few days. Count the number of slugs under and around each square. Multiply the numbers by 10 to get an estimate of slugs per square metre.

Thresholds: If an average of more than one slug per trap is found, the slug problem is significant. If more than eight slugs are found per trap the problem is severe.

Timing of control: Slugs are best controlled before the crop is planted. Ideally, fallows should be bare so the only food source for slug is the baits. For this reason, baits applied post-emergence are less effective than pre-emergent baits, as slugs often prefer the emerging seedlings.

Chemical control: Take action two weeks before planting if there is significant slug activity in the pre-crop fallow. Two equally effective bait types are registered for slug control in field crops, those based on metaldehyde, e.g. SlugOut and those based on iron chelates (EDTA complex), e.g. Multiguard.

Metaldehyde based baits are highly toxic to mammals and birds (Schedule 5 poisons) and must be spread evenly to avoid heaping, which attracts non-target animals. Metaldehyde based products are registered in pulses for use prior to and up to the 4-leaf stage.

Iron chelate based baits are specific to slugs and snails (molluscs) and slaters (crustaceans) and have low toxicity to mammals and birds (no poison schedule). They have no impact on carab beetles, which are key snail predators and hence are the preferred IPM option. Iron chelate based compounds are registered for use in the bare fallow prior to planting, and in crop boundaries.

Protecting animals and birds: While of low toxicity, iron chelate baits are attractive to some animals and birds. The bait’s mild alkalinity may cause certain animals to vomit, especially dogs. For this reason, spread the bait evenly to avoid heaping, which might attract dogs and birds.

Insecticides sprays for other soil pests: Sprays targeting armyworms and cutworms are ineffective against slugs. Where there is extreme slug pressure, baits alone will not bring slugs under control.

Cultural control: Cultural practices that discourage slugs and snails include cultivation (two shallow discings) to bury trash and levelling the seedbed with a roller to crush clods. Don’t use press wheels as these create a humid furrow in the soil. These strategies are at odds with zero/minimum till and stubble retention practices aiming to conserve soil moisture. However, cultural practices to reduce high slug numbers may have to be employed periodically, as chemical control alone is unlikely to eliminate slugs in farming systems that retain stubble blankets.

Slug identification: To help build up a national slug incidence database, and to determine which species are causing problems in NE Australia, please collect and forward slugs to Australian slug expert Michael Nash at CESAR, Bio21 Institute, Melbourne University, 30 Flemington Rd., Parkville, Victoria 3010. Ph 0383 442 521. Mob 0417 992 097 manash@unimelb.edu.au . Post/courier slugs in a jar with moist paper and record the location (including GPS coordinates). Also record the soil type, paddock history (e.g. zero or minimal till or regular cultivation) and the paddock’s cropping history.

Mice

Mouse damage to soybean crops is an ongoing and costly problem in many areas such as the Darling Downs. Soybean crops are especially vulnerable, as they are often the last of the summer crops to mature and consequently are the only food available. Crop damage from mice is often unnoticed until it is severe. Signs of mouse activity include chewed stems or damage to seed pods. Debris such as seed husks at the base of plants suggests the damage to seed pods has been caused by mice rather than insects or birds. You can also monitor mice with mouse bait cards (https://www.daf.qld.gov.au/__data/assets/pdf_file/0003/74262/MouseHouse-BaitCard.pdf).

Zinc phosphide grain baits are now registered for use in soybean and other grain crops. It is an inorganic compound that rapidly breaks down in the presence of the stomach acids to release the toxic gas phosphine. Mouse death usually occurs within two hours of ingestion.

Contact BioSecurity Queensland on 13 25 23 or refer to the DAF website for further details on the use of these baits. https://www.daf.qld.gov.au/__data/assets/pdf_file/0003/84144/use-of-agricultural-chemicals-rodenticides.pdf

5. Natural enemies

Natural enemies of insect pests are often other insects, referred to as beneficial insects. A beneficial insect may be a predator or a parasitoid. Spiders, birds and insect diseases are also classified as natural enemies.

Insect predators consume several to many prey over the course of their development, they are free living and are usually as big as or bigger than their prey. Predators may be generalists, feeding on a wide variety of prey, or specialists, feeding on only one or a few related species.

Insect parasitoids are similar to parasites but, while true parasites usually weaken but rarely kill their hosts, parasitoids always kill the host insect. In contrast to predators, parasitoids develop on or within a single host during the course of their development.

Most parasitoids are highly host specific, laying their eggs on or into a single developmental stage of only one or a few related host species. They are often described in terms of the host(s) stages within which they develop. For example, there are egg parasitoids, larval parasitoids, larval-pupal parasitoids (eggs are laid on or in the larval stage of the host, and the host pupates before the host dies), true pupal parasitoids, and a few species that parasitise adult insects.

Conserving or encouraging natural enemies is important because a great number of beneficial species exist naturally and help to regulate pest densities. The widespread injudicious use of non-selective insecticides can decimate natural enemy populations and lead to a flaring of pests. The widespread use of non-selective pesticides can also negate classical biological control introductions, such as the tiny wasp Erotmocerus hayati imported by CSIRO to control silverleaf whitefly.

Among the practices that help conserve and favour natural enemies are the following:

• Recognising beneficial insects. Learning to distinguish between pests and beneficial insects is the first step in determining whether control is necessary.

• Minimising insecticide applications. Most insecticides kill predators and parasitoids along with pests. Natural enemies are often more susceptible than pests to commonly used insecticides. However, many newer pesticides are far more selective than the older products they are replacing.

• Using selective insecticides or using insecticides in a selective manner. Several insecticides are toxic only to specific pests and are not directly harmful to beneficials. For example, microbial insecticides containing different strains of the bacterium Bacillus thuringiensis (Bt), are toxic only to caterpillars, certain beetles, or certain mosquito and black fly larvae.

• Maintaining ground covers, standing crops, and crop residues. Many natural enemies require the protection offered by vegetation to survive. Ground covers supply prey, pollen, and nectar (important foods for certain adult predators and parasitoids), and protection from the weather.

Use of the predator to pest ratio in spray decisions

The predator to pest ratio (as developed in cotton) gives a rough guide as to the potential impact of beneficials, especially against helicoverpa and similar caterpillars. Calculation of the ratio includes helicoverpa eggs and very small (VS) plus small (S) larvae (1–7 mm) per metre assessed using visual and beat sheet sampling. It does not include medium (M) or large (L) larvae since many of the common small predatory insects are not effective on these stages (but predatory shield bugs still are). Total predators per metre are assessed using a beat sheet and visual check. To be confident in the ratio, at least three of the most common predators should be present per sample including ladybirds, red and blue beetles, damsel bugs, big-eyed bugs, assassin bugs, predatory shield bugs and lacewings.

The predator:pest ratio is calculated as:

Predators/(helicoverpa eggs + larvae (VS + S))

If this ratio is 0.5 or higher, then predators will generally provide effective control of Helicoverpa spp. If the ratio is less then 0.5 then beneficials may still give useful partial control of helicoverpa, and should still be preserved through the use of soft selective pesticides if helicoverpa are above-threshold.

Key parasitoids and predators

Key identification resource: Good Bug, Bad Bug 

Correcting beat sheet counts for sampling inefficiencies

Beat sheet sampling may underestimate the numbers of small helicoverpa caterpillars present. However, sampling inefficiencies are likely to be cancelled by increased mortality for the early caterpillar instars (up to 90%).

Converting sample totals for different row spacing

Most thresholds are expressed as pests per square metre (pests/m²). Hence, insect counts in crops with row spacing less than one 1 m must be converted to pests/m² as follows:

To convert to pests/m² divide the ‘average insect count per row metre’ across all sites by the row spacing in metres. For example, in a crop with 2 GVB/m on average, and 0.5 m row spacing, divide 2 GVB by 0.5, i.e. 2/0.5 = 4.0 GVB/m².

Keeping records

Sampling data

Accurately recording sampling data is critical for good decision making and being able to review the success of control measures. Record or check sheets should show the following:

• numbers and types of insects found, including number of adults and immature stages

• size and stage of insects – this is particularly important for larvae and nymphs

• date and time

• weather conditions

• crop observations, e.g. crop stage, crop vigour.

This is particularly critical if an insecticide treatment is required, to assess the efficacy of the spray with a post-spray check.

Spray operations

Details of spray operations should include:

• date

• time of day

• conditions (wind speed, wind direction, temperature, presence of dew and humidity)

• product used, including batch number

• product rate and water rate

• method of application including nozzle types and spray pressure

• any other relevant details

• location of downwind non-target sites, e.g. pasture, other crops, houses.

Consider putting the data collected into a visual form (e.g. graphs) that makes it easier to see trends in pest numbers and plant condition over time. Seeing whether an insect population is increasing, static or decreasing can be useful in deciding whether an insecticide treatment may be required.

To facilitate acceptance in export markets, the soybean industry has developed a ‘grower declaration form’ where details including insecticides used, and spray and harvest dates are recorded. These forms MUST be filled in correctly.  

8. Insecticides

Insecticide characteristics

Insecticides are a key pest management tool in soybean crops. However unnecessary spraying, or selection of the wrong pesticide, can flare secondary pests, hasten the development of pesticide resistance, contaminate the harvested product, increase operating costs and reduce profitability. Both short- and long-term factors must be considered, even in a relatively short duration crop such as soybean.

• Be aware of current insecticide groups/types, and of any recent de-registrations.

• Attributes of key registered insecticides.

• Key factors to consider when making the choice.

• How to make rational post spray assessments.

• Legal aspects and responsibilities.

Insecticide groups

Insecticides can be grouped according to how they enter the target pest, their mode of action, and their chemical composition (insecticide group or family).

Route of entry – how they enter the target pest

• contact 

• ingestion

• inhalation (fumigants)

To be effective, contact pesticides need to be absorbed through the external body surface. This contact can be either directly at the time of spraying, or indirectly with the pest picking up dried spray residues as it moves over the surface of the plant. 

Many insecticides have both contact and ingestion activity, though one may be more important than the other. Some newer generation ‘soft’ insecticides (e.g. Steward, TracerII) are only ‘activated’ inside an insect’s gut. This is one reason they can have a reduced impact against many beneficial insects.

Systemic pesticides are those that can be moved (translocated) from the site of application to another site where they become effective, e.g. insecticides that are absorbed by foliage and translocated throughout the plant. Chewing and sucking pests will then ingest the insecticide along with plant tissues or fluid. Dimethoate is an example of a systemic insecticide. Other insecticides such as chlorantraniliprole (Vantacor) have ‘translaminar’ activity and can reach pests inside leaves or inside flowers. Pests inside pods are much harder to kill.

Mode of action, i.e. how they kill pests and the body systems attacked

• Neurotoxins – most insecticides, e.g. pyrethroids, organophosphates and carbamates.

• Metabolic inhibitors – interfere with essential body processes such as moulting. 

• Insect growth regulators – are slower acting. Includes many of the newer generation ‘soft’ insecticides registered in cotton (but not in pulses).

• Physical toxicants – such as oils, abrasive dusts. 

• Biological infection – by ingestion e.g. NPV (Helicoverpa virus) and Bt (bacterial toxin) or through the pest’s cuticle e.g. Beauvaria and Metarhizium fungi.

Chemical structure (classification)

Insecticides are also grouped according to the chemical similarity, especially for the purpose of designing resistance management strategies.

The main insecticide groups to consider in soybean crops and other summer pulses are:

• Diamides, Group 28 e.g. chlorantraniliprole (Vantacor).

• Oxadiazines, Group 22A, e.g. indoxacarb (Steward EC), a new generation product with low mammalian toxicity.

• Spinosyns, Group 5, e.g. spinosad (TracerII), a new generation low mammalian toxicity product that has been withdrawn from Australian grain/pulse crops for commercial reasons.

• Emamectins, Group 6, e.g. emamectin (Affirm), abamectin (Wizaard 18).

• Neonicitinoids, Group 4A, e.g. clothiadin (Shield) and dinotefuran (Starkle).

• Sulfoximines, Group 4C, e.g. sulfoxaflor (Transform).

• Carbamates, Group 1A e.g. thiodicarb (Larvin), methomyl (Lannate, Marli) and pirimicarb.

• Organophosphates or OPs, Group 1B, e.g. chlorpyrifos (Lorsban) and dimethoate (Rogor).

• Synthetic pyrethroids or SPs, Group 3, e.g. deltamethrin (Decis), alpha cypermethrin (Dominex etc.).

• Biopesticides, e.g. NPV (ViVUSMax) and Bt (DipelSC, Group 11). 

Making insecticide choices 

When confronted with an above-threshold pest population, there are several factors to consider when selecting from the available insecticides. These include:

• Whether the product is registered

• Efficacy against the target pest

• Susceptibility of the crop to pest damage at the time in question

• Impact on natural enemies

• Impact on bees

• Resistance management status and conditions 

• Ability to control multiple target species

• Withholding periods and Export Slaughter Intervals

• Rainfastness

• Impact on stressed plants

• Toxicity to the environment and humans

• Exclusion zones

• Cost – both long- and short-term

Product registration

Only use products that are registered or have an APVMA permit for use in the crop being grown. Check the APVMA website https://apvma.gov.au/node/10831 

Efficacy

A well-chosen insecticide is one that gives good control, while minimising negative side effects such as the development of resistance or flaring secondary pests. Efficacy is often judged by the percentage kill and speed of kill. While many contact insecticides have a rapid knockdown effect, others (particularly those that rely on ingestion) have a period, often measured in days, before maximum kill is achieved. Users need to be aware of these differences between products.

The stage or size of insect targeted also influences efficacy, with larger insects generally more difficult to control. For example, the ‘Critical Comments’ on the Steward label state ‘Target brown eggs and hatchling (neonates to 1st instar) to small larvae (2nd instar) when they reach the economic spray threshold and before they become entrenched in pods.’ 

Another important factor in determining efficacy is the level of residual control provided. Some insecticides provide very little residual control (e.g. dimethoate, methomyl), while others can provide residual control in the order of weeks if conditions are favourable, and where there is little growth dilution (e.g. Vantacor and, to a lesser extent, Steward). Efficacy also depends on getting the chosen product onto the target site, whether that is on the insect directly or the plant surfaces from where the insect picks up the insecticide.

Susceptibility of the crop to pest damage

If a crop is at a stage more tolerant of pest attack, e.g. with 33% defoliation tolerable during the vegetative stage, there is no need for 100% pesticide efficacy. In this case a biopesticide with a 70% efficacy such as ViVUSMax for helicoverpa, will suffice. This approach has two benefits – beneficial insects are conserved and more effective products such as Vantacor are reserved for later crop stages (e.g. flowering to pod fill) that are more susceptible to pest attack.

Impact on natural enemies

In soybean crops, there are benefits in choosing the softer option where possible. Going soft early with highly selective products, e.g. NPV or Bt, conserves beneficial insects for later on when the crop is more susceptible to attack. Going soft early reduces the risk of flaring pests such as helicoverpa, and the need for follow up sprays to control those pests. Note also that some insecticides impact on some beneficial groups more than others. For example, Steward has a low impact on predatory bugs but a major impact on ladybirds. As a general rule, the recommendation is to hold off using harder insecticide as long as possible – Go Soft Early!

Resistance management strategies for your region or a particular product

In soybean crops and other pulses, resistance management strategies place restrictions on the number of sprays per crop, rather than on the timing of applications (as in cotton). A specific example of a label restriction is:

From the Steward label: ‘No more than one (1) application per crop’.

Following the resistance management guidelines for helicoverpa in particular is essential to ensure that this pest does not develop resistance to any current or new products. Refer to: Resistance management strategy for Helicoverpa armigera in Australian grains https://ipmguidelinesforgrains.com.au/important/uploads/GRDC_RMS_Helicoverpa-Armigera.pdf 

Post-spray assessments

Once crops have been sprayed for pests, it is essential to conduct post-spray assessments to ensure that a satisfactory level of control was achieved. Good control is usually >90% for chemical pesticides, and 70% for biopesticides. Conduct the post-spray assessment as soon as the specified re-entry period allows entry to the field. For most products this is 2 to 3 days after treatment (2–3 DAT). However, with biopesticides, mortality may not occur until 5–7 DAT. Crops sprayed with chemical pesticides should be checked again at 7 DAT to check for re-invasion and check biopesticide-sprayed crops again at 10–12 DAT. Regular twice-weekly sampling should continue until the crop is no longer susceptible to pest attack.

Sprays sometimes fail to work as effectively as required or expected. This can be due to several reasons, e.g. a bad batch of product, poor coverage, bad timing, adverse weather conditions, poor water quality, insecticide resistance, too-high expectations of the product selected, pesticides that have passed their use by date, and pesticides that have been stored in hot conditions.  Application problems (coverage, timing, water) and inappropriate product selection account for a large percentage of failures. Where a spray failure is suspected, detailed records can assist in trying to determine what might have been the cause of the apparent failure.

Spray failures are often due to heavy pest pressure. Where GVB pressure is high, crops are often re-infested by nymphs hatching from the large number of GVB eggs present but not controlled by spraying. This frequently occurs even where crops are sprayed with deltamethrin (e.g. Decis).

Re-infestation will also occur where there is prolonged helicoverpa pressure and crops are sprayed with products that have no impact on moths, and/or have very little or no residual activity, e.g. biopesticides. Uncontrolled moths may continue to lay more eggs, which give rise to more larvae that survive because there are no pesticide residues to kill them. It is also possible that pests have come in post-spray from elsewhere, particular if there is a lot of activity in surrounding crops.

Apparent spray failures may also occur where pesticides are unable to reach the target pest, or where the damage has been inflicted before spraying occurs. An example of this is where small helicoverpa larvae are feeding inside flowers. Short residual pesticides such as methomyl usually break down before the majority of larvae emerge, resulting in imperfect control.

Legal issues

This section discusses some of the legal issues surrounding insecticide usage, but is by no means exhaustive. Specific questions should be followed up with relevant staff in the Queensland Department of Agriculture and Fisheries, who have responsibilities in the area of advising on agricultural and veterinary chemical use.

Registration

Insecticide users should be aware that all insecticides go through a process called registration, where they are formally authorised (registered) by the Australian Pesticide and Veterinary Medicine Authority (APVMA) for use:

• against specific pests

• at specified rates of product

• in prescribed crops and situations where risk assessments have evaluated that these uses are:

  • • effective (against that pest, at that rate, in that crop or situation) 

    • safe (in terms of residues not exceeding the prescribed MRL (Maximum Residue Level), and safe to the crop itself (no phytotoxicity). 

    • not a trade risk.

Labels

A major outcome of the registration process is the approved product label, a legal document that prescribes the pest and crop situations where a product can be legally used, and how. Always read the label! The use of products for purposes or in manners not on the label involves potential risks. These risks include reduced efficacy and exceeded maximum residue limits (MRL), which can have trade implications and the risk of litigation.

Be aware that pesticide-use guidelines on the label are there to protect product (grain) quality and Australian trade by keeping pesticide residues below specified MRLs. MRLs in any crop are at risk of being exceeded or breached where pesticides:

• Are applied at rates higher than the maximum specified.

• Are applied more frequently than the maximum number of times specified per crop.

• Are applied within the specified withholding period (WHP), i.e. within the shortest time before harvest that a product can be applied.

• Are NOT REGISTERED in the crop in question.

All of the above have the potential to jeopardise the marketing of Australian pulse crops.

Material Safety Data Sheets (MSDS)

Material Safety Data Sheets (MSDS) are essential reading. They document the hazards posed by the insecticide, and the necessary and legally enforceable handling and storage safety protocols.

Permits

In some cases a product may not be fully registered but is available for use under a Permit with conditions attached, which often require the generation of further data for eventual full registration.

APVMA

The national body in charge of administering these processes is called the APVMA (the Australian Pesticides and Veterinary Medicines Authority) and is based in Canberra.

Details of product registrations and permits are available via the APVMA’s website https://apvma.gov.au/node/10831 

From the APVMA website:

“The APVMA administers the national Registration Scheme for Agricultural and Veterinary Chemicals. The scheme registers and regulates the manufacture and supply of all pesticides and veterinary medicines used in Australia, up to the point of wholesale sale.

The APVMA sets maximum residue limits (MRLs). An MRL is the highest concentration of an agricultural or veterinary chemical residue permitted in food or animal feed. MRLs are used to check whether chemical users are following the directions on the label. MRLs are usually set well below the level that would harm health. When an MRL is exceeded, it usually indicates a chemical is being misused, rather than a public health or safety concern.

State and territory governments regulate the use of agricultural chemicals after they have been sold. These regulations cover:

• basic training requirements for users

• licensing of commercial pest control operators and ground and aerial spray operators

• residue monitoring

• arrangements to enforce the safe use of chemicals, including the use of codes of practice, spray-drift guidelines and other user awareness raising initiatives.” 

End of extract the APVMA website.

State Government regulations are relevant in determining the legality or otherwise of deviations from label conditions.

Where soybean crops are grown in new production areas, e.g. The Burdekin, they may encounter new pests for which registered chemicals (or permits) are not always available. 

Insecticides registered or under permit in soybeans (October 2022)

Always check product registrations and permits via the APVMA’s website https://apvma.gov.au/node/10831 

9. Making control decisions

Making control decisions may seem daunting given: a) the number of pests attacking soybean plants; b) the uncertainty of what might happen if you do nothing; and c) the number of pesticide options available. However, decision making is easier if you break it down into the following logical steps.

1. What stage is the crop?

This will tell you in advance what pests are likely to be a problem in the crop and if the crop is susceptible to a given pest at that stage.

For example, podsucking bugs won’t be an issue in vegetative or even flowering crops

2. What pest(s) is/are present? – this is CRITICAL

Is it one of the major pests, e.g. helicoverpa or podsucking bugs

These are the ones to worry about most. Make sure you can tell the difference between the major and minor pests, and beneficial insects.

3. Are there any other pests present? 

For example, are there cluster caterpillar present?

Other pests might be controlled by what is applied to control the main pest, alternatively the other pests might not be controlled, or they could even be flared if the wrong pesticide is used.

4. What size/stage are the pests?

Pest size can be critical as some pesticides, particularly biopesticides, are only effective against the early stages of the target pest. E.g. ideally target helicoverpa ≤7 mm with NPV.

Note that to catch pests when they are still small, sample regularly, particularly in hot weather when pests grow more quickly.

5. What type of damage is observed in the crop?

This will provide further clues as to the identity of the pest, and the severity of the infestation.

Ensure the pests are still present and still feeding (not pupating).

6. How large and vigorous is the crop?

A large vigorous crop is better able to compensate for damage than a small, stressed crop.

For a given podsucking bug population, a high-yielding soybean crop with a large number of set pods and seeds will suffer lower % seed damage than a small crop with fewer pods. Use the DAF on-line calculator, to enter the variety and the expected yield, and the calculator will calculate the podsucking bug threshold specific for your crop.

7. Are the beneficials insects present keeping the pest/s in check?

Beneficials insects may be holding other key pests in check – such as aphids and whitefly.

• Look for evidence such as parasitised whitefly nymphs, diseased caterpillars, predatory bugs attacking caterpillars, and the failure over time of small caterpillars to progress to large ones.

• Ladybirds are often a good indicator of aphids as being orange, they are much easier to see than soybean aphids, which are green.

If so, you need to consider using a more selective option that has minimal impact on the beneficials and doesn’t flare whitefly or other pests.

Alternatively, the beneficials may do the job for you, so keep checking the crop to monitor their progress.

Beneficials are often very good pest indicators. E.g. if lots of ladybirds are present there will either be aphids or whitefly present in your crop.

8. Are the pests above-threshold?

If not, it is uneconomic to spray.

If not much above-threshold, you might consider a biopesticide if one is registered. This would be particularly appropriate for helicoverpa in vegetative soybean crops when a near perfect kill is not required, and a 60–70% kill will be sufficient to bring the pest down below threshold (6/m²).

If pests are well above-threshold, you will need a product with high efficacy (85–90% kill).

Use the recommended sampling protocols so that the pest counts can be accurately compared to thresholds derived using the same sampling protocols.

9. Are there any resistance management guidelines for the pesticide being considered?

Has the pesticide been used previously in the crop? Remember that for helicoverpa, apply only one chemical insecticide group per crop.

10. How close to harvest is the crop? 

As you get closer to harvest pesticide withholding periods (WHP) must be considered. If time to harvest is shorter than the WHP for a particular pesticide, it is no longer legal to spray that pesticide in the crop.

11. Will the stubble be grazed post-harvest?

• If a crop is to be grazed post-harvest, export slaughter intervals (ESI) may come into play.

• These can be markedly longer than the crop WHP.

• Export slaughter intervals also come into play if adjoining crops/pasture are contaminated with the pesticide.

12. Can the pesticide be delivered to the target?

• Do you have the right nozzles, spray volume and pressure to penetrate the canopy?

• Do you have good quality spray tank water, i.e. close to neutral?

13. Are the weather conditions right for the pesticide being applied?

Check the wind speed, temperature and UV levels.

14. What is the risk of off target contamination?

• Consider the weather conditions – check for high wind speed and temperature inversions.

• Proximity to other crops/pasture – check the exclusion zones distances.

• How close is the neighbour’s house? Is the wind blowing toward or away from sensitive areas.

15. What about the applicator’s safety?

• What safety gear is required?

• Has the operator read the MSDS for the pesticide in question?

• Remember, some older pesticides such as methomyl are extremely toxic.

16. Post-spray assessments

• Always make post spray assessments to determine the efficacy of whatever pesticide is applied.

• For fast-acting pesticides, check crops a soon as the re-entry period elapses.

• For slow-acting pesticides (e.g. biopesticides) wait until significant mortality is likely.

Control decision examples

Example 1: You find on average 7.5 medium small (<12 mm) Helicoverpa armigera larvae per metre of row (0.75 m row spacing) in vegetative soybean crops 5 weeks after planting. The crop is growing well with good moisture and spined predatory bug (Oechalia sp.) counts are averaging over 2 per metre. There have been reports of silverleaf whitefly (SLW) in the district. They are also in your crop but not yet in damaging numbers.

The decision steps are as follows:

• Crop stage – mid vegetative and healthy (well-watered) so well able to cope with early damage.

• Pest species – Helicoverpa armigera is potentially very damaging as larvae attack the axillary buds, which are the precursors to the floral buds. 

• Threshold – the population of 7.5/m in 0.75m rows equates to 10/m² (10 = 7.5/0.75) and is above the new helicoverpa threshold of 7/m² during the crop’s vegetative stage. Because the rate of damage is severe once this level is exceeded, it is necessary to bring the population down below threshold. However, as there is no yield loss below this threshold, it is not necessary to kill every larva in the crop.

• Pest size – Congratulations! Larvae were detected while they are still small enough to kill with a biopesticide, and before they have inflicted significant damage.

• Beneficial insects – the predatory bug numbers are high enough to provide useful control. 

• Other pest threats – The presence of SLW in the crop means it is important to avoid flaring them with ‘hard’ pesticides such as the SPs (e.g. deltamethrin/Decis, Ballistic).

• Pesticide selection – remember the ‘Go Soft Early’ guidelines for vegetative soybean crops. Given the beneficials in the crop, the SLW threat and the threshold guidelines, the IPM-friendly option is to apply a Helicoverpa virus formulation (VivusMAX or Gemstar). Remember in this scenario, a perfect kill is not required to protect crop yield. Also, the healthy state of the crop means it will compensate for this level of defoliation. 

Example 2: You find on average 2 redbanded shield bugs (Piezodorus – RBSB) per square metre, and numerous dark twin row egg rafts indicative of this species. The crop is just beginning to set pods and there are no caterpillar pests. What do you do? Spray now to get on top of them – or wait?

The decision steps are as follows:

• Crop stage – the crop is not yet susceptible to podsucking bug attack as there are no seeds set yet for PSB to damage. Also, because pod set is not completed, there is no way to predict the likely yield, an agronomic parameter required for the threshold calculator.

• Bug numbers – the number of adult RBSB (2/m²) suggests the RBSB bug population is already above-threshold and may be higher by pod fill. But remember, the thresholds only come into play at the onset of pod fill.  

• Bug stages – the RBSB eggs already present may not be killed by current PSB insecticides, and a follow-up spray might be required, targeting hatching nymphs. Also, newly hatched (1st instar) nymphs don’t feed and thus don’t pose any risk until early pod fill.

• Pesticide selection – there are three potential options – (i) deltamethrin, (ii) clothianidin (Shield), or (iii) Skope – which has dual bug/caterpillar activity.

• Decision – monitor the crop closely and delay spraying until early pod fill. By that time, many of the egg rafts may have hatched and the hatchling nymphs will now be vulnerable to insecticides. A single spray (saving money) may provide sufficient control. Whatever option is chosen, always add a 0.5% w:v salt (NaCl) adjuvant to improve the pesticide performance. 

If the RBSB population has increased by pod fill, clothianidin (Shield) is the preferred option as, with the 0.5% salt adjuvant, it will give ≥80% control. In contrast. deltamethrin plus salt gives only 60% control, and thus could leave post-spray populations still above-threshold (2*0.4 = 0.8). Because no caterpillars were present, the preference is for a single-focus insecticide, rather than a dual activity product. Also, the dual action product here (Skope) has a 42-day WHP in soybean crops.

Note: RBSB are a problematic pest and are far more difficult to control than green vegetable bug (GVB) for which deltamethrin gives over 90% control. Therefore, be sure to differentiate between GVB and RBSB. The latter are a paler (more yellowish) green than GVB, and are considerably smaller. Also, GVB do not have a transverse band across their shoulder.

Note also that it is only the female RBSB that have the transverse red band, and that in the tropics, many females have the white band that typifies the male RBSB. 

10. Key resources

• Good Bug? Bad Bug? – an identification guide for pest and beneficial insects in summer pulses, soybeans, peanuts and chickpeas 2012 edition (new edition in 2023) https://thebeatsheet.com.au/wp-content/uploads/2012/04/GoodBadBug-FINALscreen22Feb3.pdf 

• Understanding Helicoverpa ecology and biology in southern Qld – know the enemy to manage it better (2005) https://www.daf.qld.gov.au/__data/assets/pdf_file/0005/72689/Insects-Helicoverpa-ecology-biology.pdf 

• Microplitis demolitor and ascovirus: – Important natural enemies of helicoverpa (2005) https://www.daf.qld.gov.au/__data/assets/pdf_file/0011/50699/Insects-Microplitis-ascovirus.pdf 

• Parasitoids: Natural enemies of helicoverpa (2005) https://www.daf.qld.gov.au/__data/assets/pdf_file/0003/64677/Insect-Parasitoids-Natural-enemies-helicoverpa.pdf 

• Using NPV to manage helicoverpa in field crops (2005) https://www.daf.qld.gov.au/__data/assets/pdf_file/0007/76876/Insects-NPV-to-mange-helicoverpa.pdf 

• Resistance management strategy for Helicoverpa armigera in Australian grains https://grdc.com.au/resources-and-publications/all-publications/publications/2018/resistance-management-strategy-for-helicoverpa-armigera-in-australian-grains