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Agricultural Research Service

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Corn rootworm

Corn Rootworms Will Die for Watermelon

By Judy McBride
May 21, 1998

The juice from a bitter watermelon would gag most people. But it tastes like a hot fudge sundae to corn rootworms.

Agricultural Research Service scientists identified the ingredient in the juice that causes the insect to gorge. They developed a process for extracting the active ingredient along with the juice and combined the solution with a red dye that's deadly to rootworms but safe for people and animals.

In preliminary field tests last summer, the watermelon-dye combo took a promising bite out of the costliest insect pest in the U.S. Three days after application, it had killed 85 percent of adult rootworms compared with 65 and 70 percent for two other controls--both pesticide-bait combinations.

Corn rootworms cost U.S. farmers $1 billion annually in lost crops and control measures. Farmers apply pesticides on 30 to 40 million acres--often as a preventative measure--to keep these little gluttons from leaving their crops without a root to stand on.

Researchers at the Beltsville, Md., Agricultural Research Center wanted a control that would spare the environment and foil the rootworms from developing insecticide resistance. ARS entomologist Robert Schroder and colleagues have applied for a patent on their formulation. The watermelon-dye combo zeros in on the adult stage of the insect. This breaks the reproductive cycle so next year's population is lower.

The lethal agent is the same D & C Red Dye No. 28 approved by the Food and Drug Administration for use in drugs and cosmetics. It is now in the registration process, in combination with a different kind of bait, for controlling fruit flies.

ARS studies with the dye have been conducted under cooperative research and development agreements with PhotoDye International Inc., of Baltimore, Md. A story about the research appears in the May issue of Agricultural Research magazine. The story is also on the World Wide Web at:


Scientific contact: Robert F. W. Schroder, ARS Insect Biocontrol Laboratory, Beltsville, MD 20705-2350; phone (301) 504-8369, fax (301) 504-8190,

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Last Modified: 8/22/2017
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