Control Techniques - Herbaceous

Control Techniques

Introduce various approaches to invasive plant control, including mechanical, chemical, biological, and cultural control. Prior to the presentation, you’ll need to identify which techniques are appropriate for your situation. Spend additional time explaining the techniques you’d like participants to you use.

Mechanical control is the physical act of removing the plant. Examples include hand-pulling, cutting, or mowing. Mechanical control methods are often used in conjunction with chemical control techniques, which utilizes chemicals, such as herbicides, to disrupt a plant’s growth cycle.

Biocontrol is a technique whereby an invasive plant’s natural predator(s), such as insects or diseases, are purposely introduced to an area to “naturally” control the plant. Potential biocontrols are studied and tested extensively before they are released. For example, there is a beetle that feeds on the leaves of purple loosestrife (an invasive wetland plant with bright purple flowers), which negatively affects purple loosestrife growth and seed production.

Lastly, introduce the concept of cultural control. Cultural control is a shift in human activity to promote favorable growing conditions for desirable plants while reducing the inadvertent promotion of invasive plant populations.

Managing Expectations

Talk to participants about the scale of the invasive species problem. Eradication is often impossible due to off-site factors. For example, road-side mowing spreads invasive plant seeds or humans inadvertently transporting seeds on shoes or cars. Humans have a dramatic impact on our landscapes and our general tendencies favor the continued establishment and expansion of invasive species. Communicate to participants that it is important to manage expectations. Successes are possible and expected, but monitoring and follow-up are required.

Decontamination

When doing invasive species work, be aware of the potential to inadvertently spread invasive species. Inspect and remove plants, animals, and mud from your boat, trailer, vehicle, equipment, and gear (DiVittorio et al., 2012). Dispose of unwanted plants and animals in a responsible manner. If possible, scrub all equipment to free it of sediment or debris. Rinse with tap water when possible. If possible, decontaminate at the site location.

Herbicide Use

Communicate to participants the importance of properly following herbicide instructions. It is against federal law to use herbicide in a manner inconsistent with the label. Personal Protective Equipment (PPE) is required. Use the herbicide you (the trainer) use as an example and discuss the potential risks – both to the applicator and to the plant. Explain how the herbicide affects plant growth (this is different for each herbicide and you will want to research your specific herbicide).

Selecting a method

Select a technique(s) that (1) minimizes risks of contact to the applicator and others that may be in the area during and after herbicide application, AND (2) minimizes release of herbicide to the environment, particularly if the herbicide could contact non-target species.

If spill occurs, use kitty litter to absorb the liquid. Dispose of all contaminated litter in a trash bag OR spread the material at the legal rate or concentration.

Protective gear for applicators:

The health and safety of the applicator are of foremost concern. Applicators MUST wear all protective gear required on the label of the herbicide they are using. Any additional safety and protective gear requested by applicators must be provided.

• Inspect all PPE for rips or tears before each use. If equipment is torn or unsafe, dispose of immediately.

• Chemical resistant gloves must be worn when handling any herbicide or any herbicide contaminated equipment. Recommended materials for gloves include: vinyl, PVC coated, or nitrile.

• Wear eye protection when mixing and at any other time when splashing or spraying may occur.

• If needed, wash gloves and protective suits before removing to avoid contact with skin.

• Be sure all PPE is clean before storing.

• Leather boots are permeable. Wear rubber over-boots when needed (especially for “wet-glove” and foliar spray).

• Wash hands and face thoroughly after doing any work with herbicides or herbicide equipment.

• Masks (for particulate matter) are available and recommended for foliar spray treatment and mixing. Some applicators may even wish to wear respirators where not required. A dust mask may be worn when a respirator is not required, but pesticide safety officers point out that dust masks usually fit loosely and do not stop volatile compounds. Furthermore, they can indirectly increase chances of exposure if they cause heating, sweating, and irritation, which induce the wearer to repeatedly wipe or scratch their face.

General Safety Recommendations

Tell participants to (1) Wear PPE at all times because there is always a chance for unintentional contact; (2) Mix only the amount of herbicide he or she will be using in a given day; (3) Do not spray into the wind, as this increases the likelihood of blowback; (4) Be aware of your surroundings as they apply (for example, don’t spray upwind from a neighboring vegetable garden; (5) Do not spray above head level. This increases the likelihood of exposure to herbicide; Use a respirator when using widespread spray applications (e.g. boom sprayer) (6) ALWAYS wash hands after handling herbicides.

Cleaning Equipment

All equipment should be thoroughly rinsed following an application. This prevents herbicide residue build up and corrosion of equipment. Use fresh water to fully rinse out the reservoir tanks, taking special care to rinse seals and threaded caps, and flush spray lines. Capture all rinsate (water used to rinse) and store it. Rinsate can be used to mix up the next batch of the same herbicide solution. Be sure to label rinsate to avoid any confusion.

To dispose of rinsate, designate a ‘waste area’. This is an area free of pets, children, or other human contact and contains sediments to which the herbicide can bind. Note that the rinsate will harm vegetation. Examples of disposal sites are to dispose of rinsate into a gravel driveway or spray it onto undesirable vegetation (an invasive species).

Handling Spills

“The faster you can contain, absorb, and dispose of a spill, the less chance there is that it will cause harm. Even minor dribbles or spills should be cleaned up to minimize exposure. Spill management is based on “Three C’s”: Control, Contain, and Clean up. (Unit 11, Ohio State University Extension 1992).

1. Control the Spill Situation - make sure that the spill has stopped. 

   • Put on appropriate personal protective equipment before coming in contact with the spill. 

   • Stop the source of the spill by placing the smaller container into a larger chemical-resistant container if possible.
     

2. Contain the Spill Situation - stop the spill from spreading.

   • Isolate the spill site by keeping children, other unprotected people, and animals well back. 

   • Use a mound of dirt or other material to make a dike around the edge of the spill.

3. Clean Up the Spill: 

   • Do not use water. It will spread the spill and make it worse. 

   • Soak up liquid spills with absorbent materials such as cat litter, vermiculite, or chemical sorbent fabric. 

   • If the pesticide or absorbent material is likely to blow around, moisten it very lightly with water or cover with a tarp. 

   • Collect the spill and cleanup material into plastic containers or drums.”

Selecting a method

Select a technique(s) that (1) minimizes risks of contact to the applicator and others that may be in the area during and after herbicide application, AND (2) minimizes release of herbicide to the environment, particularly if the herbicide could contact non-target species, AND (3) effectively treats the target species.

Consider the weather:

• • (1) Herbicide efficacy is reduced when moisture is present or impending (i.e. dew or rain). Do not use foliar applications when dew is present or rain is expected. Cut-stump, basal bark, frill/hack and squirt, drill and fill, mowing/cutting, hand-pulling, and spot burning can all be used when precipitation is expected (to be safe, allow 4-hour window between last application and precipitation). 

  • (2) Wind, rain, and humidity all have an effect on the effective of any given technique. It is a complex and inter-related relationship, the details of which are beyond the scope of this workshop. Ask participants if they have questions. The provided workshop contacts can help answer specific and detailed questions.

General Considerations

These methods apply herbicide directly to the leaves and stems of a plant. An adjuvant or surfactant is often needed to enable the herbicide to penetrate the plant cuticle, a thick, waxy layer present on leaves and stems of most plants. We strongly recommend using an adjuvant or surfactant. Ask participants to define an adjuvant or surfactant. An adjuvant is an additive to improve herbicide effectiveness. A surfactant is an adjuvant that helps break the bonds of the mixture to better spread the mixture across the leaf/stem. In effect a surfactant “Makes water, wetter”. There are several types of foliar application tools available. Ask participants to name a few.

Foliar application of herbicide should be handled with great care. It is a violation federal law to use an herbicide inconsistent with the product label. Additional certification is required to be a commercial herbicide applicator, and participants would want to thoroughly research state and federal laws to learn more.

You will be surprised at the amount of drift that can occur from a sprayer. This causes the potential for damage to non-target species. Participants and managers will need to consider weather conditions and timing of the foliar treatment.

When the weather is either too hot or too cold, the efficacy of the foliar herbicide application can be reduced. As a general rule, when the temperature exceeds 90°F, a plant will close the small pores (stomata) in the surface of leaves and stems to conserve water. The amount of herbicide taken up by the plant will be reduced. At the other end of the range, when the temperatures drop below freezing the plant reduces cellular activity and herbicide efficacy is reduced. It is important, however, to communicate to participants that this is highly variable and changes for different species and sites.

In some circumstances, foliar application during dormancy of native plants is preferable because it reduces the likelihood of damaging other non-target plants. Share the following example with participants: You can treat garlic mustard with a foliar spray on warm winter days if no snow is present. This will ensure that non-target damage to other plants doesn’t occur because they haven’t yet emerged. Garlic mustard is a plant that stays green throughout the winter, which means treatment can happen when the rosettes are exposed.

Spot/Backpack Spray Applicators

Spray herbicide directly onto target plants only, and avoid spraying other desirable plants. These applicators range from motorized rigs with spray hoses to backpack sprayers, to hand-pumped spray or squirt bottles, which can target very small plants or parts of plants. Crook-necked squirt bottles and similar equipment can be ordered from laboratory supply companies and are easy to carry over distances and through dense vegetation.

Grid and Spray Technique – When applying foliar herbicide, it can be difficult to keep track of where you have sprayed and where you have not. 

• First, figure out the dominant wind direction. You’ll want to keep the wind behind you.

• Start at the downwind end of the area to be treated.

• Treat in lines that are perpendicular to the dominant wind direction, which allows you to always be spraying with the wind at your back.

• It is helpful to mark the end points of each spray line to help keep you oriented. It can be difficult to keep track of where you’ve treated and where you need to cover. You can use existing trees or landmarks, or you can mark spray line ends with a flag or marker tape.

• Work your way back and forth along the spray lines from the downwind to upwind ends of the treatment area.

Detailed Instructions

• The person that is lined up next to the stakes will guide to them and nothing else and will start moving first. 

• Each following person will stay about a wand length away from the person ahead of them. 

• Make sure to stay in the diagonal so that you can be as precise as possible. 

• Move as quickly as the group as a whole can move. Getting ahead of the other will cause lines to be stray off course. 

• The guide person will pass the stake down the line to the next person until it reaches the last person, who will then set the stake at the edge of their spray line. 

• Once everyone has arrived at the last stake, you will reset the line in reverse order.

• Repeat these step until the unit is complete

Use a sponge or wick on a long handle to wipe herbicide onto foliage and stems. Use of a wick eliminates the possibility of spray drift or droplets falling on non-target plants. However, herbicide can drip or dribble from some wicks.. This treatment method is typically for woody species but has been adapted for herbaceous control such as large diameter vines. 

Glove of Death

The “glove of death” is a technique for applying herbicide in an otherwise high quality site. Herbicide is sprayed directly onto a heavy cotton glove worn over a thick rubber/latex (or nitrile) glove. The wearer of the glove can then apply the herbicide with total precision and little or no runoff. This technique is not recommended for heavy infestations, simply because it would require a lot of manual work. Land managers with light infestations often choose this technique because the equipment is cheap, the technique is simple and not much manager oversight is needed.

Key Points:

• Be aware of the potential damage to non-target plant species and plan foliar application accordingly. Wind carrying spray off-target, rain washing herbicide off before plant absorbed, and over-spraying onto desirable species are all examples.

• As a general rule, the efficacy of the foliar herbicide application reduced when temperature exceeds 90°F or falls below freezing (32°F). Glyphosate does not volatilize readily, but triclopyr does so be aware of chemicals and their temperature tendencies. Below freezing, the water used to dilute chemical starts to freeze. This can be mitigated by mixing with oil or other liquids with lower freezing points.

• Choose a technique that effectively treats the target invasive species.

• Utilize spray lines to keep track of where you’ve treated and work from the downwind to upwind ends of the treatment area.

This method is used most often as part of an integrated approach. Rarely will mowing or cutting effectively control invasive species in isolation. The primary purposes of cutting or mowing are to reduce the above-ground biomass or to stop a species from going to seed.

A mower can be as simple as a basic lawn mower all the way to a tractor and industrial-strength brush-hog. For cutting, a weed-whip or brush-cutter is recommended. A weed-whip is a light-duty often gas-powered implement with a high-speed rotating plastic wire, which cuts grasses and flowers well. A brush-cutter is heavy duty and is intended to cut small woody shrubs. It is useful for infestations of tougher species (phragmites is an example).

Communicate to participants the importance of understanding plant physiology when considering mowing or cutting. Infestations of certain plants, for example Japanese Knotweed, are exacerbated when cut (root and stem fragments re-sprout). Improperly applied or timed applications can spread the target invasive species.

You (or participants, depending on your approach) will need to decide whether it more appropriate a mower or a weed-whip. With large infestations, it is more efficient to use a mower, assuming the ground is dry enough to support the mower. In situations with sparse or patchy infestation, a weed-whip/brush-cutter is better suited.

Key Points

• A primary purpose of mowing/cutting is to reduce above-ground biomass to make follow-up chemical treatment more effective.

• A second primary purpose of mowing/cutting is to stop a species from going to seed.

• It is important to understand plant physiology to not accidently spread the target invasive species.

• You (or participants, depending on your approach) will need to decide whether it more appropriate a mower or a weed-whip/brush-cutter.

This is the simplest method for participants to engage with. It is often used for small infestations, in highly sensitive areas, or on particularly susceptible species. Site assessment and intended outcomes are particularly important with this technique. Some species are particularly susceptible (example, garlic mustard), some root systems do not allow for hand-pulling (example, phragmites), some plants contain toxic substances (example – knapweeds), and soil-type plays a significant role in the effectiveness of hand-pulling (example, rocky or dense, clay-rich soils). The key with the hand pulling method is to remove as much of the root as possible, which requires consideration of plant susceptibly and site conditions.

The technique is fairly simple and is very similar to the technique many participants have likely used to weed a vegetable garden. Grasp the plant at the base, as close to the ground as possible, and gently pull upward to uproot the plant. Participants could use of a small spade and “pop” the tap root. Depending on the species, hand pulling results in roots being broken off (especially in harder soils).

You should also communicate to participants the importance of minimizing soil disturbance. Participants could tamp down disturbed soil with their foot or hand after removing the plant, but this can be time consuming. Communicate the balance between minimizing soil disturbance and forward progress.

Ask participants what they think should be done with the uprooted plant. Depending on the species, the stage of growth, and the presence of seed, some uprooted invasive plants may be left in the field. This is a complicated decision, requiring in-depth knowledge in the plant’s habit. The safest choice is to remove the invasive plants from the field and dispose of them. You should take a moment to re-iterate the previous points. You can advise participants to bag the plants in a trash bag or burn them in a fire (as applicable).If left in the field, several species will utilize the energy stored in the root to go to seed.

Reiterate the following key points, as necessary:

Key Points:

• Hand-pulling is often used for small infestations, in highly sensitive areas, or on particularly susceptible species.

• Hand-pulling is a great method to use where other native plants are present or where more intensive methods are not appropriate.

• Grab at the base of the plant as close to the ground and gently pull upward to uproot the plant. Consider “popping” the taproot with a small spade. The goal is to remove as much of the root as possible.

• The safest choice is to remove the invasive plants from the field and dispose of them.