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Scientists explore using predator insects to eat pests

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Spiders eat pests off vegetable plants

Spiders are a natural predator insect that eat pests off vegetable plants in high tunnels.

URBANA, Ill. — The flourishing local foods movement is driving more Illinois farmers to grow fruits and vegetables, using high tunnels to extend the growing season. All that fresh produce in an enclosed space makes insect outbreaks common.

To help growers protect their investment, University of Illinois Extension is researching how to use predator insects to control pests.

Bronwyn Aly, an Extension local food systems and small farms educator in Southern Illinois, knew local farmers needed a safe, efficient, and cost-effective way to deal with pests in high tunnels. This need prompted her to reach out to University of Illinois researcher Kacie Athey, assistant professor in the Department of Crop Sciences, for a solution.

The question is, can other insects — their natural predators — be used to control pests?

“There isn’t a lot known about how effective these predators are in high tunnels,” Athey says in a news release.

So, she, Aly, and Matthew Turino, crop sciences research specialist, teamed up to find out.

In Illinois, fruit and vegetable growers are relying on high tunnels to meet the growing demand for fresh, local foods. To control pest outbreaks, many guides recommend using a pesticide followed by the release of predator insects, but many insecticides are not labeled for high tunnels and many growers worry about exposure risks in a semi-enclosed space.

Farmers and gardeners have introduced natural enemies of pests to control insect populations, an approach called biological control, for centuries. In a two-year project that started the summer of 2021, the research team released insect predators in high tunnels with tomatoes, peppers, and a few other crops. They wanted to see if and how they affected pest populations of spider mites, aphids, whiteflies, and thrips.

“These are very common pests in greenhouses and high tunnels, and they are good candidates for this project because these are the type of pests that can continue to outbreak when you spray insecticides,” Athey says.

The researchers released three species of enemy insects into the high tunnels once a month: insidious flower bug (Orius insidiosus), a mite (Amblyseius swirskii), and two-spotted lady beetle (Adalia bipunctata). These species are already established in the U.S.

The results are promising so far. The number of aphids, whiteflies and leafhoppers decreased in high tunnels where predators were released.

They found the insidious flower bug was eating aphids, thrips, whiteflies and spider mites. The predator mite was eating thrips, whiteflies and spider mites. The lady beetle, which is expensive to buy, ate aphids but was never found again after they were released.

This summer, the research team will use what they learned to further pinpoint useful biological control agents. Aly says they also plan to compare the costs of biological controls and pesticides.

“That is going to be a big question for high tunnel growers. They’re going to want to know how well it works and also the cost of it,” Aly says.

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