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Combating Corn Borers

sanandreas
Image: Department of Entomology, University of Nebraska-Lincoln

Every summer the larvae of a tiny insect known as the European corn borer (right) wreak havoc on American corn crops, costing farmers nearly a billion dollars annually. But researchers may have found a way to combat these voracious pests without costly insecticides. The results of a new study, which will be submitted to the Journal of Biological Control, indicate that the early release of an army of wasps just once in the season can reduce corn damage by half.

Farmers typically release legions of Trichogramma ostriniae wasps throughout the growing season. The wasp parasitizes the corn borer egg by depositing its own egg inside, killing the corn borer embryo in the process. Eventually two wasps emerge from the borer egg and the cycle is repeated. But Cornell University entomologist Michael Hoffmann and his colleagues demonstrated in field tests that if done early enough in the season--when the corn is knee-high--a single dispatch of about 30,000 wasps per acre can suppress the borers. The total cost of this release, they report, amounts to less than that for a single insecticide treatment.

Under ideal circumstances, the wasps would become permanent residents in the cornfields, potentially eliminating the need for even yearly releases. But in upstate New York, where the tests were conducted, the wasps do not survive the harsh winters. Still, Hoffmann remarks, "maybe further south they will overwinter and become established."

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