Pesticides and IPM

There was once a time that, if there was a pest problem, the school would rely on its maintenance staff to go down to the local hardware store and purchase a brightly colored tube depicting cartoons of heroic exterminators spraying gigantic roaches and rats into an agony of oblivion.

Not anymore. Integrated Pest Management (IPM) has an entirely different approach. This is articulated in the Environmental Protection Agency's very thorough manual, IPM for Schools, produced for USEPA (Document #909-8-97-001) by the Bio-Integral Resource Center, Berkeley, Calif. In this approach chemical controls are minimized, used only when needed and in the least-toxic formulations possible. The emphasis is on biological, cultural, physical, mechanical and educational methods used in site-specific combinations to solve the pest problem.

"In a nutshell, dealing with pest issues is similar to preventive health care," says Lyn Garling, program manager for the pest management program at Penn State University, University Park, Pa., and affliliated with the IPM Institute of North America, Madison, Wis. "If you are reactive to only the symptoms, you don't cure the underlying problem and may very well add to it."

The good news is that there are more and more environmentally friendly ways to eliminate pests without harming the human population, and there is an abundance of information on how to go about it. The bad news is IPM is a very comprehensive and complex subject.

Garling says that pest control is no longer a simple matter to be left to the maintenance staff, but rather everyone, including the facility manager, key administrators, teachers and others have a role to play It may be helpful for a school to have an ongoing health and safety committee. Regular and in-depth training must be provided to key personnel. This is a real area for education. Because 32 states have IPC laws for schools, of which many schools are not aware.

Outsourcing to an outside pest management company is an option, but may also have its downsides, especially if they are paid for doing more when doing less intelligently is the wiser option, and the communications between the two entities are not properly maintained.

"There are some 60 to 70 accidental invaders, so if you seal them off, that goes a long way to reduce the need for pesticides," says Dawn Gouge, associate professor of community IPM at the  University of Arizona, Maritoca, Ariz. "There are many simple measures that many people are not aware of. For instance, the many security lights around school entrances attract insects, unless they are tinted with yellow (which doesn't attract them.) And teachers tend to store their materials in cardboard boxes, but they should be thrown out at least every two years. For they make nice cozy environments for rodents and cockroaches, especially in the winter."

Gouge says there is an ever-increasing availability of pesticides that have low or no acute or chronic toxicity to humans, affect a narrow range of species,and are formulated to be applied in a manner that eliminates exposure of humans and other non-target organisms. Examples include products formulated as baits, pastes or gels that do not volitalize in the air, that utilize very small amounts of the active ingredient pesticide and are best set in traps that cut off exposure to humans.

Also, there are microbial pesticides formulated from fungi, bacteria or viruses that are only toxic to specific pest species but are harmless to humans.

Both Gouge and Garling agree that each school should articulate a comprehensive pest management program.

The following is drawn directly from the IPM for Schools manual, which provides illustrative examples for the four key pest management questions in the decision-making process — if, where, when and which.

If Treatment Action Is Necessary

Instead of taking action at the first sign of a potential pest, the IPM process begins with asking whether any actions are needed. Sometimes, even a fairly large population of pests can be tolerated without causing a problem. In other cases, the presence of a single pest organism is considered intolerable. In still other cases, what is considered a pest by one group in society may be considered innocuous by another.


For example, Boxelder bugs (Leptocoris trivittatus) are brightly colored and often cluster under shrubs, on the shady side of tree trunks or enter buildings through open doors or broken window screens The sight of them sometimes frightens people, or raises fears that they will damage plants. In fact, these insects are harmless. They feed mainly on boxelder trees and silver maples, and rarely harm even these trees since their main food source is the tree's seeds. Thus, concern about their presence is generally unwarranted.

Or, as another example, large rodent dropping and grease trails suggest there is a rat in a crawl space under the eaves. Even one rat can be a problem because it can gnaw on electric wires causing fires, and leave fleas that can transmit pathogens to humans. Treatment action is usually required even if only one rat is suspected.

Where Treatment Activity Should Take Place

If it is decided that some treatment action is necessary, the IPM process encourages pest managers to look at the whole system for the best place to solve the problem. Treatment should be applied where actions will have the greatest effect.

For example, although mosquito problems are frequently handled by fogging buildings or schoolyards with insecticides, it is not possible to control mosquitoes unless treatment is directed at the immature stages of the insect. Mosquito larvae develop in water (e.g., clogged gutters, drains, stagnant ponds, low-spots in playing fields, etc.). By locating such sites and eliminating them or treating them with non-toxic microbial materials to kill the larvae, mosquito problems can be solved before mosquitoes become biting adults, without exposing the school community to potentially hazardous pesticides.

When Action Should Take Place

The timing of treatments is important. Often, there is an optimal time in the life cycle of the plant or the pest to apply control measure. Conversely, there may be times when treatments actually increase pest problems. The human social system will also affect the timing of treatments. The IPM process encourages managers to discover the best timing for treatment actions, since the long-term success of any treatment depends on timing and locating it properly.

For example, the timing in the life cycle of a plant, like Rose powdery mildew (Spacrotheca pannosa) usually infects only succulent young growth on roses. Because mature leaves are rarely attacked, treatments are only necessary when growth spurts occur, and only new foils requires treatment.

Or, as an example of timing in the life cycle of the pest insect, BT (Bacillus thuringiensis) is a naturally occurring bacteria developed into a commercial insecticide to control caterpillar pests. It must be applied to leaves when caterpillars are small and actively feeding in order for them to consume the bacteria and die. If BT is applied when caterpillars are large, they may have already stopped eating in preparation for spinning cocoons.

There is also the importance of timing in the social system. When switching to IPM, it is essential to coordinate the IPM program plan with the overall budget process of the school district. For example, improving rodent and fly management may require modifications in food storage facilities or in the disposal of kitchen garbage. Substantial repair to windows or plumbing may be needed. Requesting funds for minor construction, new containers, etc. must be done at the appropriate time in the school district's budget development process.

Which Mix of Strategies and Tactics Are Best?

There are three guiding principles to use when choosing treatments — conserve and enhance naturally occurring biological controls, use a multi-tactic approach and view each pest problem in its larger context.

Conserve and Enhance Naturally Occurring Biological Controls

In a landscape setting, when we kill the natural enemies of pests, we inherit their work. In many cases, combined action of all natural enemies present may result in substantial pest control. Even when they are not able to do the complete job, natural enemies are nonetheless providing some help in protecting school landscape plants from pest insects. The IPM program should be designed to avoid damaging natural enemies.

For example, many spider mite populations on various trees and shrubs are kept under control by naturally occurring predatory mites. In fact, the predators keep them under such good control we may never be aware of their presence until we spray a pesticide intended to kill more obvious pests, such as aphids. For a number of reasons, most pesticides are more harmful to the predatory mites than the pest mites. The pesticide kills almost all of the predators, the spider mites are only slightly affected, and now that they are free from their natural enemies, the pest mites quickly multiply and devastate the plant. By changing the tactics for controlling the aphids, a spider mite problem can be avoided.

Use a Multi-Tactic Approach

Every source of pest mortality, no matter how small, is a valuable addition to the program. Biological systems are so complex, rarely will a single tactic, such as the application of a pesticide, solve the problem for long. As many non-toxic tactics as possible should be combined to manage the pest problem.

For example, controlling cockroaches requires direct tactics such as applying boric acid dust to cracks, crevices and wall voids; placing baits in areas inaccessible to students; using an insect-growth regulator and boric acid water washes in areas not in direct contact with food or people; and releasing parasitoids for certain roach species. But long-term cockroach control must also include habitat modification such as caulking or painting closed cracks and crevices, screening vents that may be used by cockroaches to travel between adjacent areas, eliminating water leaks and cracks around plumbing fixtures and improving the storage of food supplies and organic wastes.

View Each Pest Problem in Its Larger Context

Each pest problem must be considered within the framework of the larger system in which it has arisen. Textbooks and manuals commonly treat pest problems one by one. However, in the "real world" setting of a school and the grounds around it, pest problems occur several at a time or in a sequence in which management of one influences the others. In addition, pest problems are influenced by other human activities such as waste disposal and food handling indoors, and mowing, fertilizing and irrigating outdoors, as well as the attitudes of many people who work and study within the district.

For more information, visit Integrated Pest Management (IPM) in Schools, National School IPM Information Source or the National Pesticide Information Center.

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