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Good Growing

Pest Management in the Garden

home garden

Warm weather has arrived, and our plants are starting to green-up and bloom. That also means weeds, insects, and diseases are starting to become active too. As the saying goes, the only things guaranteed in life are death and taxes, and if you're a gardener, you can also include pests in the list of life's guarantees.

When faced with some of these pest problems this year, consider using integrated pest management (IPM). IPM is an approach to reducing insect pest, weed, and disease populations to an acceptable level (we don't typically 'wipe out' the pest) using a variety of different techniques. There are four techniques used with IPM: cultural, physical/mechanical, biological, and chemical.

The idea behind cultural management is growing and maintaining a healthy plant. A healthy plant is less susceptible to disease and they are better able to withstand attacks from insects and competition from weeds. This means growing the right plant in the right place at the right time.

Make sure you are planting plants that are appropriate for the site they will be planted in. Don't plant something that needs full sun in shade or that requires acidic soils in alkaline or neutral soils. Placing a plant in the wrong environment can prevent the plant from reaching its full potential and will likely lead to a weak plant that has more than its fair share of insect and disease problems. If you have known disease problems in an area, looking for resistant cultivars to these diseases can help reduce problems you may have (this can also work for some insects). In addition to selecting the right site for your plant, make sure it is getting the proper fertilization and enough, but not too much, water (too much water causes as many problems as not enough). You can also alter the time of your planting to avoid a particular pest. For example, plant summer squash in early July to avoid squash vine borer because they have finished laying eggs by then. Some other cultural management techniques are pruning, sanitation, and mulching (just don't make volcanoes).

The goal for physical/mechanical management is to physically eliminate pests. This can be done in a variety of different ways, such as hand-picking Japanese beetles, bagworms, or other caterpillars; pruning out diseased branches, webworms, or galls; pulling or hoeing weeds in flower beds or vegetable gardens; or putting up barriers to prevent pests from getting to your plants such as bird netting or fencing for rabbits and deer.

In biological management, pests are managed with other living organisms (often called natural enemies). Ladybeetles (aka ladybugs) eat small, soft-bodied insects like aphids, scale, and mealybugs. Lacewing larvae sometimes referred to as aphid lions, feed on aphids, scale, mealybugs, small caterpillars, and occasionally mites. There are tiny parasitic wasps, too small to sting people, that lay eggs inside of aphids, and when the eggs hatch, the larvae eat the aphid. There are other parasitic wasps that lay eggs on caterpillars. You may have seen these in your garden before if you grow tomatoes; infected hornworm caterpillars will have a mass of what looks like eggs on them, but they are actually cocoons. If you see this, don't get rid of that caterpillar; eventually, the wasps will emerge from the cocoon and will go on to attack more caterpillars. Like plants (and us), insects can also be infected by fungi and bacteria, which may help manage their populations.

The final management technique used is chemical. The goal is to manage pest populations by using pesticides, whether it is an insecticide, fungicide, herbicide, etc. If you are using IPM, chemicals should only be used as needed. In some cases using pesticides may be the best option to manage a particular pest. However, often times one of the three other techniques (cultural, physical/mechanical, and/or biological) can be used to manage pests. If you do go the pesticide route you want to try and use pesticides that are the least toxic possible. Before using any pesticide product, make sure to read the label. The label will tell you where you can legally use it, what it will control, how much you should use, how often you should use and any precautions you need to take while using the product.

Good Growing fact of the week: In addition to prey, many natural enemies need sources of pollen and nectar, particularly the adults. By planting plants that are attractive to them such as dill, cilantro, fennel, cosmos, and blanketflower you can encourage them to stick around.


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Ken Johnson is a Horticulture Educator with University of Illinois Extension, serving Calhoun, Cass, Greene, Morgan, and Scott counties since 2013. Ken provides horticulture programming with an emphasis on fruit and vegetable production, pest management, and beneficial insects. Through his programming, he aims to increase backyard food production and foster a greater appreciation of insects.