Manna from heaven it wasn't. But the powder drifting down from the sky--as part of a research study--was an appetizing surprise to western corn rootworm beetles. They immediately switched to it from the corn leaves they'd been munching. Then they died.

The "manna" was powdered roots of wild buffalo gourds. It was sprayed from crop-dusting airplanes on thousands of acres across the Corn Belt this summer. Cucurbitacins in the gourd roots--compounds partly responsible for the musky smell of cantaloupes--stimulated the beetles to feed on the powder. Unfortunately for them, it was laced with a tiny dose of insecticide.

This summer's spraying marked the first year in a large-scale, five-year test of this alternative to conventional insecticide use against the rootworms. The new technique uses up to 98 percent less carbaryl insecticide than conventional applications. Most of the 20 million acres of U.S. cropland threatened by the corn rootworm is treated with much higher doses of insecticide.

Scientists with the Agricultural Research Service say the new approach lowered beetle numbers. Some fields had to be re-sprayed with the powder because of heavy infestations--up to 30 adult beetles per plant.

The true test will come next spring, when offspring of this year's adult beetles start hatching, according to entomologist Larry Chandler. He's at ARS' Northern Grain Insects Research Laboratory, Brookings, S.D.

Chandler is technical coordinator of the five-year corn rootworm areawide management program. The program, funded by the U.S. Department of Agriculture and several universities, supports USDA's goal of having farmers use integrated pest management (IPM) on 75 percent of the nation's cropland by 2000. IPM combines many control strategies--including nature-based tactics such as gourd root powder--instead of relying on pesticides alone.

An article on the rootworm program appears in the October issue of ARS' Agricultural Research magazine. The article also is on the World Wide Web at:

http://www.ars.usda.gov/is/AR/archive/oct97/corn1097.htm

Scientific contact: Laurence D. Chandler, ARS Northern Grain Insects Research Laboratory, Brookings, S.D., phone (605) 693-5239, fax 693-5240, lchandle@ngirl.ars.usda.gov.