Monitoring pests and determining when to begin control helps keep damage below damaging threshold levels. Correctly identifying the pest is important for selecting effective biological or chemical controls.
Denying pests food, shelter, proper temperature, and other basic needs reduces their numbers and damage. Physical and cultural practices can help manage pest problems, too. For more information, click Here.
Biological control uses living predators, parasites, disease pathogens or competitors to suppress pest populations and damage without the use of chemical pesticides. In general, these organisms are referred to as “natural enemies.” Biological control tactics differ widely depending on the target pest, environmental conditions, and pest life cycle. They are grouped into three general approaches:
Importation or classical biological control is where natural enemies from the target pest’s place of origin are brought to a new area, often in order to replace those that have been destroyed by natural selection or other factors. This is the approach most frequently used in greenhouses, nurseries and some fruit and vegetable fields to manage insect pests and weeds.
In some cases, a natural enemy is simply introduced to a crop when the population of the target pest is low. This is sometimes called delaying a pest’s attack. It can be effective against certain crops with critical windows of development (bud burst, flowering, etc).
A third approach to biological control is augmentation or “enhancing” existing populations of natural enemies in an attempt to increase their ability to suppress pests. Augmentation is most common in field crops such as grapes, tomatoes and squash.
The goal of augmentation is to increase the number or effectiveness of natural enemies in an area by mass-rearing and/or releasing them in large quantities. This is most often done in the form of pathogens, but also includes predators and parasitoids.
Biological controls are most effective when used as part of a multifaceted Integrated Pest Management program. Biological control tactics can help reduce the amount of chemical pesticides used, especially in the home landscape, and provide valuable ecosystem services such as soil fertility improvement. They can also be used to supplement other control strategies, such as the introduction of herbicide resistant crops, genetically modified plants, pheromone disruption techniques and botanical insecticides.
To maximize the benefit of biological control, gardeners should be aware that natural enemies are living organisms with their own needs. To encourage them, gardeners should provide suitable habitat, including a variety of plantings that the natural enemies will find attractive and a water source.
Chemical Management
Chemical pest control involves using substances that kill or repel a pest population. The term pesticide covers a wide variety of compounds, including herbicides that kill plants, insecticides that kill insects, fungicides that kill fungi and rodenticides that kill rodents. The majority of chemicals are synthetic, but some natural organic products can also be considered pesticides. All pesticides must be carefully selected and used according to the label instructions in order to reduce risks to people, pets and nontarget organisms that may be harmed by the chemicals.
Chemicals that work by poisoning a pest have roots in history that stretch back centuries. The use of lime, wood ash and nicotine was common in the 1600s, while arsenic and mercury were popular options during the 1920s. Synthetic chemical pesticides became more popular with the advent of DDT in the 1930s, but issues with safety and environmental damage caused by misuse quickly emerged.
Modern chemical pest control treatments are designed to be safer and more environmentally friendly than ever before. With low-dose options and strict safety standards, they can be an effective last resort for many difficult pest infestations. They are categorized as plant protection products in the United States and must be registered for each use.
While physical methods of pest control can provide a more immediate solution to pest problems, they do not offer long-term results and may require significant staff resources to maintain. In addition, they are less reliable than chemical options in controlling a pest problem once it has started.
Biological pest control methods are often more effective than chemical options in reducing a plant-feeding insect population and can be applied to large areas. However, they can take much longer to produce results and are often more expensive.
While there are a wide variety of biopesticides, the most commonly used biological agent is bacillus thuringiensis (Bt). This bacterium produces a toxin that kills caterpillars by destroying their midguts. It can be found in a variety of formulations and works against over 400 different insect species without harming humans or pets.
Physical Management
A physical approach to pest management involves blocking access to food and water, excluding pests from areas and eliminating hiding places. This can be done through trapping or the use of barriers such as fences, screens and other material. Pests can also be repelled by chemicals, such as attractants or predators, or by sound and visual devices. Physical controls can also include sweeping up or vacuuming pests from surfaces and in storage areas. The physical aspect of pest management can also involve ‘pest proofing’ facilities by sealing openings, installing doors with tight-fitting hinges and using other materials that prevent entry or exit of pests.
The first step in any pest management program is accurate identification of the pests to be controlled. This is important because a pest’s characteristics affect its behavior and life cycle, and how it responds to control methods. Knowing the pest’s preferred foods, water sources and habitats, for example, can reveal weaknesses in its population that may be exploited.
Once a pest is identified, monitoring must begin. Regular inspections of the area where the pest is found are essential to discovering and correcting conditions that favor it. A flashlight is useful for checking dark or secluded areas where the pest hides, and a magnifier is helpful in identifying insect parts and frass (excrement). Frequently inspected spots should be recorded and any unusual findings should be noted.
An important part of this monitoring is to determine the level of damage that is unacceptable. This level is called a threshold and must be established before any action is taken to manage the pest. Once a threshold is established, it can be used to select the best chemical, biological or physical control method.
Some pests are continuous and require continuous management. Others are sporadic or cyclical and need to be managed only periodically. Many pests are also resilient and adaptable, surviving or even increasing in numbers when conditions are favorable for them. Therefore, a successful pest management program must incorporate all methods of control to achieve sustainable results. This requires an integrated approach known as Integrated Pest Management (IPM). It is an approach that uses information about pests and available control methods in a way that minimizes risks to people, property and the environment.
Integrated Pest Management (IPM)
When pests occur, IPM uses a combination of preventive and curative actions. It begins with monitoring plants for signs of pests and then identifies the specific plant species or genotypes being attacked by those pests. This information is then used to determine the most effective control measures for that particular pest. IPM plans take into account a variety of control options including chemical, biological, and cultural methods. The goal of an IPM plan is to suppress pest populations below the point where they cause economic injury to a crop or landscaped area.
The use of IPM methods is often more environmentally responsible than the application of single-use chemical pesticides. It also helps to minimize resistance development by introducing more than one type of control method into the environment. The diversity of control strategies creates balancing selection pressures that retard the evolution of resistant pests.
Biological management is another component of IPM, and includes predators, parasitoids, and disease organisms that are naturally occurring in a field or garden ecosystem. For example, the flies that attack millipedes and grubs in a lawn or vegetable garden are natural enemies of these pests and help keep their numbers low. Likewise, natural predators and diseases that attack crop-feeding insects or mites also help to regulate pest populations.
Other forms of biological control include the use of pheromones, which mimic the hormones produced by a plant to communicate with pollinators. Similarly, soil fumigants, which contain volatile organic compounds that are toxic to pests, are an effective and non-chemical means of controlling pests.
A common strategy today to avoid resistance development is the use of multiple pesticides in a rotation or mixture. However, a recent study shows that this strategy may not be as effective as originally thought and should be reevaluated. An increasing emphasis on in-field genetic diversity, both in space and time, could be a good way to decrease resistance development as well. This would involve incorporating genetic variation into plant breeding programs for IPM purposes, as well as promoting diversity through crop and cultivar rotations. Ideally, these efforts would be done in concert with other elements of Evolutionary IPM such as the judicious use of pesticides.