Effective, Sustainable Pest & Disease Control | The IPM Approach

Many vegetables and flowers love long, warm summer days, and so do plenty of insects and diseases. Every experienced grower knows some pest and disease pressure is unavoidable. The goal is to keep it from making crops unsaleable, and the best approach is prevention, largely through an integrated plan.

Learn the pests and diseases common on your crops in your area so you know what's coming.

Start by getting informed. A good first step is contacting your state or county Cooperative Extension Service. Its job is to provide timely, practical, research-based pest management information for your region. Plenty of online resources can also help you understand likely problems and handle them before they get out of control.

If you haven't yet, see whether your state has an integrated pest management (IPM) program for the vegetables, flowers, fruit or other crops you grow. In many states the land-grant university andCooperative Extension Service provide fact sheets, training and advice on the biggest threats to commercial crops there. Some pests and diseases occur everywhere in the U.S., but regional differences can be large, so read information for your own and neighboring states.

Or you may find your state's pest and disease information inside a larger commercial crop production guide. Search that phrase with your state name to see what's available.

What you want is a crop-by-crop list of the most common pest and disease problems. Once you know the likely culprits, learn to recognize pests at every stage, from egg to larva to adult, and diseases by their symptoms. Many online publications have good photos, or to confirm what a particular pest looks like, try Insect Images, a grant-funded image library covering many economically important insects.

It's less work than it sounds, because most vegetables fall into plant families that share pest and disease problems, and rotations should be planned by family too. If you don't know vegetable families yet, see the plant family reference chart, a short guide from Virginia Tech and Virginia Cooperative Extension.

To avoid surprises this season, spend an hour now finding resources that will help you prepare for pests and diseases. Search "IPM vegetables" or "integrated pest management" plus a crop or method, and look through the results for your state and nearby ones.

IPM programs exist all over the U.S. and the world, and you can learn a great deal from regional IPM resources online. From UMASS Amherst to Oregon State University and points between (University of Minnesota), there's a huge amount of online material for anyone keen to learn IPM.

Once you know which pests and diseases can hit your crops, you can watch for them actively.

On a small, hands-on farm, make a habit of checking both sides of leaves for eggs and disease spots as you work. On a larger, more mechanized farm, set traps and schedule regular inspections for other problems. Big vegetable farms often hire IPM consultants for this monitoring, called crop scouting. At any scale, a new generation of field tools and apps can make your crop monitoring more effective.

Some states run monitoring programs for pests and diseases that threaten valuable crops. Cornell University, for example, has run pheromone trap networks for sweet corn pests across western New York, checking traps weekly and reporting on European corn borer, corn earworm, fall armyworm and western bean cutworm. Because these pests' life cycles are well understood and driven by accumulated degree days, specialists can predict outbreaks from trap counts. Sweet corn growers in the region can check the Cornell IPM website for updates, arrival forecasts and related information.

Integrated pest management is an ecosystem-based way to solve pest problems with as little risk as possible to people and the environment. As integrated suggests, the different measures in IPM often overlap and reinforce each other, and every option deserves consideration given how complex living systems are.

Nearly every pest and disease problem has a ladder of responses. Here are the main parts of the IPM framework.

Using diatomaceous earth (DE) responsibly in an ecosystem-based plan

Diatomaceous earth is made of finely ground fossil diatom shells. Its sharp edges scratch through the waxy outer layer of insects, which dry out and die anywhere from a few hours to several days later. Typical targets are soft-bodied crawling insects such as ants, earwigs, cockroaches, silverfish, crickets, fleas, millipedes, centipedes and even bed bugs.

So DE is a mechanical pesticide. Because some pests won't crawl on, land on or feed on plants dusted with it, it also works as a repellent.

Its main drawback is that it can kill beneficial insects such as lady beetles and pollinators. It also soaks up moisture, so it works less well in humid or rainy weather.

On the plus side, it has low toxicity to birds and mammals (avoid breathing the dust), and because it works physically rather than chemically, insects can't become resistant to it.

In IPM, though, the aim is to remove only the target pest, so DE isn't a cure-all; it's a fast, effective, low-toxicity option that is fairly gentle when used in limited situations.

Always read pest and disease control labels and follow them exactly.

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• Cultural controls. Once you know which problems are likely, cultural controls are easy to build in as prevention. The basics include crop rotation, clearing crop debris, adjusting planting dates to stay ahead of pests, and pruning with clean tools so infections don't spread. Many problems can be avoided from the start by building healthy soil (or a good growing medium if you're not growing in the ground) so plants are vigorous and better able to stand up to insects and disease.
• Mechanical controls. Next come physical methods: row cover, reflective mulch to repel certain pests, hand-picking, traps, stem collars, trellising, all kinds of tillage, and good airflow under cover. Solid cultural and mechanical controls together form the non-living foundation of an IPM plan.
• Biological controls. The next level is biological, starting with choosing varieties that resist problems. Biological control means bringing in living organisms (predators, parasitoids, pathogens, competitors or symbionts) to keep pests and diseases in check through predation, parasitism, feeding and crowding out.
• Chemical controls. At the top of the framework is chemical control. Spraying, even with products allowed in organic production, should be the last resort, for three reasons:

Know the economic threshold for your crop before using chemical controls.

• First, the products may cost more than the damage the pest or disease would cause.
  
  Some pests have an established economic threshold (ET), also called an action threshold. It's defined as the pest level at which control should begin to keep economic damage from exceeding the cost of treatment.
  
  Your state or regional IPM website may list thresholds for some crops. Sweet corn pests have well-studied thresholds, but for other pests you may need to rely on your own judgment and experience.
• Second, pests and diseases can develop resistance to many control products.
  
  With organic and synthetic products alike, resistance wastes useful, low-toxicity tools and pushes growers toward harsher options or total crop loss.
  
  Rotate and tank-mix products. Some products allowed in organic production also carry little risk of resistance. (More on slowing resistance in pests and diseases.)
• Third, chemical control is less and less acceptable in sustainable systems, even when products are available, effective and fairly mild, because people are more aware of the environmental costs and concerned about residues on food and ornamental crops.

For a broader view of IPM, we recommend an open-access opinion paper by Swedish plant pathologist Johan Stenberg in Trends in Plant Science, A Conceptual Framework for Integrated Pest Management.

By thinking ahead about likely pests and diseases, scouting regularly and building sensible cultural and mechanical controls into your routine, you'll grow healthier crops with fewer crises. Still, pests and diseases sometimes threaten an important crop despite your best efforts. When that happens, we carry a full line of low-toxicity and OMRI-listed products.

More information

• Integrated pest management (IPM) principles • U.S. Environmental Protection Agency
• Farmscaping basics: insectary, trap and repellent crops for pest control • Article
• The IPM triangle for crop planning • PDF
• Pest and disease controls
• Rotating crops and controls to prevent resistance in pests and pathogens Article