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University of Illinois Extension

Growing Plants to Attract Insect Predators

June 19, 2013

As gardeners trend toward more natural ways to grow small fruits and vegetables, both in the backyard and at community garden plots where traditional control products may not be allowed, insect predators can be of use, said University of Illinois Extension horticulture educator Richard Hentschel.

"There are a number of predator insects that can help us control the destructive ones," said Hentschel. "The commonly known ones include several versions of the lady beetle. Both the adults and larvae feed on aphids. Ground beetles also feed on both adults and larvae of destructive insects such as root maggots, snails, slugs, caterpillars, and weed seeds.

"Other lesser known predators are pirate bugs, damsel bug nymphs, and assassin bugs," he added. "These three feed on soft bodied insects that damage our plants. Lacewing larvae feed mainly on aphids mainly whereas the adults also use nectar and pollen as food besides feeding on aphids."

Another group of predators, not officially an insect, but an insect relative, includes spiders. All spiders do not necessarily build a typical web, Hentschel said. Those are the orb weavers, catching their prey in the web itself.

Other spiders include wolf spiders, preying on insects that move along the ground. Also included are jumping spiders, who get their name by how they attack their prey. These spiders stalk and then pounce on prey. Crab spiders will usually sit quietly waiting for prey to walk by and then reach out with their strong legs and make the capture. They can walk sideways and resemble crabs in that way, Hentschel explained.

"Spiders can be found throughout the backyard and in undisturbed areas," he said. "They do not necessarily need a favored plant but a favorable environment."

According to Hentschel, another insect that is often referred to, but is not as helpful, is the praying mantis. "This is a very interesting insect to watch, yet is not one of the better predators for the garden."

Although predator insects, such as the lady beetle, can be purchased by mail order or at a good garden center, Hentschel said the challenge is keeping them in the yard as they are mobile, and will distribute themselves around the yards nearby.

"In order to attract and keep these predator insects in and around the garden, there are a couple of conditions that need to be met or maintained," Hentschel explained. "Without a food source of destructive insects, the good guys will go elsewhere. Without a small population of their prey on your desirable plants and vegetables, there will not be a population of predator insects when you really need them.

"The other condition is a need for host plants that attract the predators into your yard. These can be cultivated flowers or more native plants. Coneflower and coreopsis are native and have interesting flowers. Cup plant and yarrow also are attractive and native. Some less ornamental plants could be wild carrot and parsnip. These two and those already noted are perennials. Anytime you have plants that self-sow, managing the plantings is really needed so you do not end up with the proverbial weed patch that can be a problem in the neighborhood or for immediate property owners."

Hentschel added that there are many more plants that can be used, depending on where the home is located. Homes in more rural settings and with larger yards have more choices, he said.

"You can find plants in the carrot, aster, mustard, and legume families that could be considered ornamentals and natives," he said. "If you are going to establish insect predator-friendly plantings, remember that you will need to take care of those plants just like you do for other plantings until they are established."

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Source: Richard Hentschel, Extension Educator, Horticulture, hentsche@illinois.edu

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