Seeking Balance In Pest Control
Gardeners know that dealing with pests, whether insect, mammal, or bird, can be an ongoing and difficult battle. To keep crops safe, farmers wield all sorts of weapons, from chicken-wire to ground cover to pesticides. New research shows that a complicated balance in the natural world involving predators may be a better alternative to some of these measures.
Research conducted at the University of Michigan by graduate student Theresa Ong, with guidance from adviser John Vandemeer, helps explain how competition between pests can establish biological control. “Competition between control agents may actually help suppress pest problems by acting as a system of checks and balances, limiting overexploitation by any one of them,” said Ong.
An example of how this competition for food sources works is best illustrated by the competition between caterpillars, parasitic wasps, and chikadees over garden plants. The caterpillar eats the plant, the wasp lays parasitic eggs inside the caterpillar, and the chickadee eats the caterpillar. All of these creatures are considered ‘control agents’ and by interacting with one another, they create a balanced system so that one species does not dominate, or completely die out.
This type of predation, called interguild predation, may be more effective than man-made efforts to reduce pests by introducing a known, specialized predator. But this approach can backfire when the predator is too effective, wiping out its own food source.