Integrated Pest Management (IPM) Part Two: How?

Integrated Pest Management (IPM) reduces pests and pest damage via coordinated pest control methods. These include anything from mulch to repellent to poison. Using IPM requires growers to consider pest issues holistically and to employ management strategies that are the most effective with the least impact on the growing environment. Today we’ll cover how to use IPM in the greenhouse or field.

Identify the pest and understand its biology.

The first step to any good IPM strategy is correctly identifying pests on your farm or in your greenhouse. Incorrectly identifying pests can lead to misusing pesticides which can cause phytotoxicity. Overuse of pesticides and fertilizer or the presence of heavy metals cause phytotoxicity in plants, which is adverse effects on growth, physiology, and metabolism. IPM is one way to thoughtfully correct pest problems and avoid phytotoxicity. 

Correctly identify pests using a hand lens or microscope. State agricultural cooperative extension services are readily available to help identify pests you don’t recognize, as are dozens of internet resources. 

Once you’ve identified the pest, understand how plants react to the presence of that pest and what the pest will look like at different stages of its life cycle. For example, mite damage can cause yellowing on leaves and leaf curling. Whiteflies can cause heavy damage like dark spotting on leaves and stunted growth. 

Monitor the pest to be managed.

Monitoring simply means systematically looking for pests. Check your stock weekly at a minimum. Daily checks are ideal. Each check should involve using a hand lens or microscope to check soil, leaves (both underside and top), and flowers for tiny pests or pathogens. Check most or all plants and separate infested plants to keep pests or diseases from spreading. Be thorough at each check and keep careful records.

Some pests can be monitored by passive means. Sticky traps will catch flying pests like thrips and whiteflies. Japanese beetles are attracted to pheromone traps. Pay attention to the weather, temperature, and humidity level to be aware of when conditions are ripe for fungus and plant pathogens. 

Determine if threshold levels have been reached. 

Finding pests doesn’t necessarily mean you should treat them immediately. Economic threshold level refers to when the cost of pest damage begins to exceed the cost of treatment. A small pest population is likely not causing a loss in quantity or quality among your crops, and you may choose to hold off on spraying your plants. The central question to determine whether to treat a growing pest population is: will this cause unacceptable harm to my plants?

Ultimately, the economic threshold is up to each individual grower. As you determine your economic threshold, consider the stage of crop development, the anticipated yield and value of the harvest, the loss of yield or damage to the crop expected because of the pest population, and the cost and efficacy of control measures. 

When a pest population meets your determined economic threshold, it is justified to treat with pesticides. Treat your plants at the economic threshold but before economic injury level has occurred. 

Summary: watch for pests and treat them as they become a more significant issue, but before they cause irreparable damage to your plants.

Consider all available control strategies.

Considering all available strategies for controlling pests is one of the central keys to IPM. A proper IPM strategy implements several controls before pesticides. These include natural controls and applied controls like biological controls, mechanical controls or exclusions, cultural controls, physical or environmental modification, host resistance or genetic control, and regulatory pest control.

Natural Controls

A natural control is a force that slows or destroys pests without human interference. Weather, topography, and natural enemies are all natural controls. Temperature, wind, sunlight, and precipitation all influence pest populations. Bodies of water and elevation can naturally attract or repel pests. Beneficial predators or insects kill pests. Farms and greenhouses commonly employ natural predators for pest control with great success. Be sure to avoid spraying pesticides after releasing beneficial predators, as many chemicals will kill good bugs along with bad ones.

Biological Controls

Biological controls are similar to natural controls, employing natural enemies to suppress pests or using methods to alter pest populations. For example, you may release a large number of sterile males to mix with the natural pest population and reduce growth. 

Beneficial predators are populations which will suppress pests and not hurt plants. Some beneficial predators include ladybugs, praying mantises, green lacewings, and the mealybug destroyer, Cryptolaemus montrouzieri. Parasitic wasps are one of the main beneficial parasites used in greenhouses. Beneficial pathogens are soil bacteria that feed on various beetle grubs and nematodes.

Mechanical Controls 

Mechanical controls are mainly exclusions — physical barriers that prevent pest activity. These include everything from screens, fences, and traps to plows and other machinery. Any means of closing up the greenhouse by sealing cracks and openings can help prevent infestations of insects, rodents, bats, birds, and other flying or crawling pests. In the field, fences can deter larger mammal pests like deer and rabbits. Machines like plows and discs physically destroy weeds in the field and can influence the presence of insects and microorganisms as well.

Cultural Controls

A cultural control alters the host plant’s environment, and subsequently the pest’s environment, to prevent or suppress infestation. Focus primarily on preventative measures as cultural controls, including growing healthy, robust plants that can withstand pests and disease, rotating crops, timing planting to avoid peak pest season, using mulch or cover crops to control weeds, and maintaining clean equipment. Thorough and consistent sanitation is also a significant help in preventing pests. Clean the concrete in your greenhouse to keep fungus gnats and other pests from laying eggs in excess wet soil. Maintaining good drainage and closed garbage containers also contributes to a more sanitary environment.

Modification

While cultural controls focus on crop environment, physical modification broadens to storage and the entire greenhouse environment. Modifications may include lowering the humidity for grain storage, killing pests or stopping them from feeding through refrigeration, and increasing airflow in the greenhouse with fans to prevent fungal growth. 

Host Resistance

Some plant varieties offer natural resistance to certain pests or even repel them. Genetic resistance can be useful on the farm or in the greenhouse by simply growing these varieties. You won’t have to spray as often if you grow plants that have been bred for genetic resistance to particular pests and diseases. 

Regulatory Control

Suppose a pest poses a risk to public health or may cause widespread damage to crops, animals, forests, and ornamentals beyond your individual greenhouse. In that case, you may want or need to participate in regulatory pest control. In this case, government agencies quarantine infested plants and employ eradication programs to eliminate the threat. In Hawaii, many plants and foods are not allowed for import because Hawaii’s endemic plants are significantly threatened by invasive species.

Chemical Control (Pesticides)

After utilizing each of these techniques, consider chemical controls if a pest population has met your economic threshold. Chemicals are typically effective and can work quickly to eliminate pests, costing less in the short term than other control methods. However, long-term pesticide use can be costly, and pesticides can kill beneficial predators. Be especially careful to vary which chemical class you use, as overusing one chemical class of pesticide can cause pests to develop resistance. 

Implement the IPM Program

As you begin your IPM program, choose the combination of methods best suited to your greenhouse or farm. Use as many strategies for prevention, suppression, or elimination as possible and don’t rely on chemicals solely or primarily. Non-chemical controls produce more effective long-term results than spraying pesticides. Try out various techniques to see what works best in your environment, and be open to new strategies as you learn more about holistically managing pests. 

Record and evaluate IPM results

Your Integrated Pest Management program will fail if you don’t keep careful records. Always . . . always . . . always record each strategy, how it is implemented, and its results. This is the only way to experiment and know what is effective and what is a waste of resources. Non-chemical methods may take longer to evaluate, but if you have an established greenhouse with no non-chemical controls, you’ll likely have rapid results from implementing non-chemical strategies. By keeping records, you can review the effectiveness of your strategies and their impact on the environment before using them again.