Rotate Crops & Controls to Prevent Tolerance in Pests & Pathogens

Effective, Sustainable Pest & Disease Control

Adopting an Integrated Pest Management Approach

Just as many vegetables and flowers thrive in the long, warm days of summer, so too do many insects and diseases. Every experienced farmer knows that some pest and disease pressure is inevitable. The challenge is to prevent pests and diseases from making crops unmarketable.

In this article, we will provide tips for controlling pests and diseases in a way that is effective and safe for you, your workers, and the environment.

Know What to Expect

Get to know your state cooperative extension agency.

Your state/county

Cooperative Extension Service

provides useful, practical, research-based information on pest management issues specific to your region


One of the benefits of having long farming experience is that you know what kinds of pests and diseases are likely to occur on your farm, so you are always on the lookout for them. For less-experienced growers, there are ample resources on the web to help you understand potential problems and deal with them before they get out of hand.

If you haven't already, check to see if your state has an integrated pest management (IPM) program for vegetables. In many states, the Cooperative Extension Service offers fact sheets, education, and guidance on the most common threats to commercial vegetable crops in that state. Although there are some pests and diseases that are found in all parts of the US, there can be considerable regional differences. So it's smart to read the information for your own state or, lacking those, for a nearby state.

Alternatively, you may find that pest and disease control information for your state is part of a larger "Commercial Vegetable Production Guide." Use that as your search term along with your state name, to see what's available for your geographic region.

What you're looking for is a listing of the most common pest and disease problems on a crop-by-crop basis. Once you know the names of potential culprits, you can learn to identify pests at all life stages, from eggs to larvae to adults, and diseases by the symptoms they cause in susceptible plants. You can find good photographs in many online publications, or, if you want to verify the appearance of a specific pest, check out Insect Images , a grant-funded service offering photos of numerous entomological species of economic interest.

This is not as big an undertaking as it may first appear, because most vegetables can be grouped into plant families with similar pest and disease problems. Rotations of vegetable crops should also be based on plant families. If you are not yet familiar with vegetable plant families, see the Referral Chart of Plant Families , a concise guide jointly published by Virginia Tech and the Virginia Cooperative Extension Service.

Stay on the Lookout

IPM Info from UMASS Amherst

IPM programs

are found across the US and throughout the world — you can learn a lot by researching your regional IPM resources on the Internet.

Once you know which pests and diseases can affect your crops, you can start actively watching for them. If you farm on a small, labor-intensive scale, get in the habit of looking at both sides of leaves when you're picking and weeding, to check for eggs and disease lesions. If you farm on a larger, more mechanized scale, you can set up traps for insects and schedule frequent inspections for other problems. Large vegetable farms often hire IPM consultants to do the monitoring.

Some states have programs to monitor for pests and diseases that are a specific threat to economically valuable crops. For example, Cornell University has set up pheromone traps for sweet corn pests in multiple locations in western New York. The traps were monitored weekly and reports compiled about the presence of European corn borer, corn earworm, fall armyworm, and western bean cutworm. Because the life cycles of those pests are well understood and are dependent on cumulative degree days, extension specialists were able to predict outbreaks based on what they found in the traps. Sweet corn growers in the region can contact the service or check the NY/Cornell IPM website for updates, predictions on pest arrival in their fields, and related information.

If you don't want to be caught by surprise this growing season, take an hour or so now to find out what resources are available to help you be prepared for pest and disease problems. Do an internet search for “IPM Vegetables” and explore the results for your own and nearby states.

Act with the Greatest of Care — 5 Key Elements of an IPM Approach

Reach the economic threshold before spraying for pests and diseases.

Understand the

economic threshold

for your crop — before applying chemical controls.

For nearly every pest and disease problem, there is a hierarchy of responses. The very best strategy is prevention, and much of that involves an integrated approach.

You can avoid many problems from the outset by improving your soil, so that plants are vigorous and robust, able to withstand insect and disease pressure. Once you know the types of problems that are likely, you can easily incorporate cultural controls as preventive measures. Cultural controls include crop rotation, cleaning up crop debris, choosing resistant varieties, shifting planting dates to stay ahead of pest development, covering crops with row cover, and using reflective mulch to repel certain pests. The second type of control strategy is mechanical, which includes such things as hand removal, trapping, and collars around stems. Next is biological control, introducing predators and parasitoids to help control pests. Finally, there is chemical suppression of pests and diseases. Spraying, even products approved for organic farms, should be a last resort for two reasons: First, the cost of the products may be greater than the economic loss caused by the pest or disease. For some pests, there is an established

economic threshold

(ET), also known as the action threshold. By definition, this is the level at which control measures should be initiated to prevent the pest from causing economic injury greater than the cost of the treatment . You may find this information for some crops on your state or regional IPM website. Sweet corn pests have well-researched economic thresholds, but you may have to use your own judgment and experience to determine the ET for other pests. The second reason to make chemical suppression a last resort is because of the potential for pests and diseases to develop resistance to many control products. With both organic and synthetic pest control chemicals, resistance devalues useful, least-toxic products and leads to ever more toxic strategies, or to complete crop failure. Strategies such as alternating and tank-mixing products should be used. There are also a number of products approved for organic production, for which resistance build-up is not a concern.
(To learn more, read about slowing the progression of pest and disease resistance .)

Be Prepared

By thinking about likely pest and disease problems early, scouting your plants regularly, and incorporating commonsense cultural and mechanical controls into your practices, you may be able to produce healthy crops with few overwhelming challenges. But sometimes, despite your best efforts, pests and diseases will threaten an important crop. When that happens, you will find a complete line of low-toxicity and organic products at Johnny's.

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