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Adult corn rootworm.

Safe Corn Pest Bait Expected to Slash U.S. Insecticide Use

By Don Comis
January 16, 1997

The U.S. Department of Agriculture and the Corn Belt states have targeted three regions for area-wide testing of a new low-insecticide bait for corn rootworms, made from wild buffalo gourd roots.

Robert Faust of USDA's Agricultural Research Service said the regions chosen are: Indiana-Illinois, Iowa-Minnesota-South Dakota, and Kansas-Nebraska. If the bait--which is commercially available--works in these states and expands to the entire Corn Belt, it could reduce total corn pesticide use by half, Faust noted.

"This test is part of an area-wide IPM (integrated pest management) research program to support the department's goal of placing IPM on 75 percent of the nation's cropland by 2000," Faust said. "Mobile pests such as the corn rootworm beetles don't respect farm fences let alone county or state borders, making IPM most effective when applied over large areas."

Faust said this is USDA's second area-wide IPM project and the first to target corn pests. "In 1995, we began a program in the Pacific Northwest to reduce numbers of codling moths, as a pest of apple and pear orchards," he said.

Typical of IPM programs, the corn rootworm bait is only used when pests reach a level at which they can significantly harm a farmer economically, tentatively set at one female beetle per plant, said Faust. Based in Beltsville, Md., he is ARS national program leader for field and horticultural crops entomology.

Corn rootworms have a fatal attraction to wild buffalo gourd roots, he said. "The roots are ground to a powder and laced with a low dose of carbaryl at a rate equal to an ounce per acre. That's 95 to 98 percent less than active ingredients used in conventional insecticide sprays," he noted.

The bait is sprayed on corn leaves which the adult rootworm beetles eat. Five years of field tests in the Corn Belt have proven the bait's effectiveness, Faust said.

Corn rootworms are the target of almost half the insecticides used in row crops in this country, requiring more insecticide than any other pest. "About 25 million acres of corn are treated each year," Faust said. "In some years, corn rootworms can cost farmers up to $1 billion in crop losses and spraying expenses."

Richard Dunkle, co-chair of the corn rootworm area-wide management ad hoc committee along with ARS entomologist Larry Chandler, said the areawide IPM concept is that "the new pest control technology that has been developed will work best if all farmers in a given area use it. We will also target other corn pests in these sites with similarly sound environmentally methods." Dunkle is acting deputy administrator of ARS.

Since farmers can't tell how many larvae are in the soil, they apply soil insecticides as a preventative measure. More than half of these treatments are probably not needed, said Chandler.

Chandler is a research leader with ARS at Brookings, S.D., where the bait was developed in 1989 by another ARS entomologist, Gerald Sutter. He has further developed and tested the bait over the past two years. Buffalo gourd roots contain bitter cucurbitacins that are unappealing to any insect except rootworm beetles, making it safe for ladybugs, bees and other beneficial insects.

Chandler said that in a South Dakota field test, the bait reduced beetle numbers so low that soil insecticide was not needed in 1994. "The bait's 'as needed' use combined with the low dose of carbaryl promise to cut total corn insecticide use in half."

Scientific contact: Robert Faust, National Program Staff, Crop Production, Product Value and Safety, Agricultural Research Service, USDA, Beltsville, MD 20705. Telephone: (301) 504-6918; fax (301) 504-6231; e-mail: or Larry Chandler, Northern Grain Insects Research Laboratory, Agricultural Research Service, USDA, Brookings, SD 57006-9401. Telephone: (605) 693-5239; fax (605) 693-5240; e-mail: