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A pest that's a chinch to return.

The chinch bug, once the plague of pioneer farmers, is making an unwelcome comeback on modern-day corn and other grain crops.

"The chinch bug was one of the country's worst pests up until the 1900's," says ARS entomologist Frank M. Davis. But environmental factors and farmers' changing cultural practices may have reduced its threat after that.

However, recent mild winters and increased grain plantings during the last decade seem to have boosted the pest's numbers in Southeastern states, particularly in Mississippi.

"The pests suck the juices from young plants, causing stunting and deformities or sometimes killing the plant," says Davis, who is in the ARS' Corn Host Plant Resistance Research Unit at Mississippi State.

Davis says ARS is trying to develop alternatives to pesticides to manage chinch bugs and that breeding plants that fend them off may offer the best solution.

He and ARS plant geneticist W. Paul Williams are fine-tuning a greenhouse-screening technique that should speed their ability to identify, and later field-test, pest-resistant corn. Williams heads the ARS unit.

"In the greenhouse, we can screen for resistant plants just about year-round," Davis says. "But out in the field, we're limited by a seasonal window of opportunity."

Researchers uniformly screen scores of corn germplasm lines by infesting seedlings with chinch bugs. The project is helped by insect-rearing technology that Davis is refining.

Each seedling is infested with a pre-selected number of chinch bugs, held within a small plastic cage that surrounds the seedling's base. A clamp and a foam-rubber stopper seal the cage without disrupting the seedling's growth.

Seven days after infesting a seedling, the researchers evaluate its reaction. They do this by visually rating the seedling, based on a damage index of 1 to 9. They also compare the growth of infested and uninfested seedlings.

Davis and Williams plan to transfer the technique and any resistant germplasm to seed companies. There, entomologists and plant breeders can develop the germplasm as commercial varieties for farmers.

Frank M. Davis and W. Paul Williams are in the USDA-ARS Corn Host Plant Resistance Research Unit, P.O. Box 5248, Mississippi State University, Mississippi State, MS 39762; phone (601) 323-2230/325-2735, fax (601) 325-8441.
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Title Annotation:chinch bug
Author:Suszkiw, Jan
Publication:Agricultural Research
Date:Mar 1, 1994
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