Pest Management
A pest species can be any species that humans consider undesirable. Any organism that reduces the availability, quality, or value of a human resource can be classified as a pest. This designation in no way reflects the organism’s role in the natural ecosystem but is more an indicator that they conflict with humans. Plant pests, also referred to as weeds, are included in the discussion of Non-native Invasive Plant Removal.
Methods of control can be categorized as chemical, biological, cultural, physical/mechanical, or genetic, and are discussed in further detail below.
Chemical. Chemicals (e.g., insecticides, herbicides, rodenticides) can be broad-spectrum (non-selective) or narrow-spectrum (selective) and can be organic or inorganic. Chemicals used to regulate pest abundance can act as nerve toxins (for insects and mammals) and growth regulators/inhibitors. Chemicals can also be used to affect pest abundance through more indirect means, such as releasing pheromones to disrupt breeding behavior and interfere with mating. Chemical pesticides are often toxic to non-target organisms including the pest’s natural enemies, can persist in the environment affecting water supply, soil productivity, and air quality, and can be biomagnified in the food chain. Inappropriate use of pesticides can result in target pest resurgence from killing off natural enemies, secondary pest outbreaks by removing natural enemies of other organisms and allowing them to rise to pest status, and evolved resistance to the pesticide.
Biological. Due to any number of reasons, including those mentioned in the Chemical and Cultural sections, compromising the effectiveness of natural enemies often allows potential pest organisms to experience virtually unregulated population growth and enables them to reach pest status. Biological control involves the use of a pest’s natural enemies (e.g., predators, pathogens, parasites, and parasitoids), to control pest abundance. Measures to conserve or enhance the impact of natural enemies should be attempted first. Perhaps biological control is most known for the importation of natural enemies, often from the pest’s area of origin, to control non-native pests (e.g., importing vedalia beetles to control cottony cushion scales which were attacking California citrus orchards). A few safeguards are necessary before implementing importation actions to ensure imported organisms will not pose additional threats to non-target organisms. The third approach to biological control involves augmenting natural enemies through rearing and periodic releases and can be inoculative (natural enemies are released early in the season) or inundate (natural enemies are released as a biological pesticide).
Cultural. The effectiveness of natural enemies can be compromised by human practices. Application of broad-spectrum pesticides which kill off natural enemies in addition to target pest species, the type of crop plant, the crop environment, and cropping practices. Modern crop varieties often inadvertently create conditions that favor pest species (e.g., pest species that have bored deeper into larger fruit making them inaccessible to natural enemies). Crops are often monocultures, consisting of a single crop species, which creates a homogenous habitat often lacking key requirements of natural enemies, thus favoring pest species. Moreover, many harvesting practices prevent natural enemies from persisting in annual crops. Examples of cultural practices that encourage natural enemies and discourage pest persistence include intercropping (multiple crops in the same field) to make it more difficult for pests to find a host plant, planting trap crops that attract pests away from harvest crops and which can later be treated with the select application of pesticides and delaying planting times to coincide with times where pests have emerged and died off for the season.
Integrated Pest Management (IPM) is an increasingly popular process for controlling pests. IPM considers the ecosystem as a whole and takes into consideration a balanced mix of control methods to produce the most effective and least damaging plan. All the methods are mutually augmentative with chemical control means as the last resort in the plan. Ideally, an IPM plan would result in a sustainable system without the need for much costly follow-up maintenance.