OCPA Research Reviews
Ken Hough, Director, Research and Market Development

Corn Rootworms Will Die for Watermelon
The juice from a bitter watermelon would gag most people. But it tastes like a hot fudge sundae to corn rootworms.

USDA Agricultural Research Service (ARS) 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% of adult rootworms compared with 65 and 70% 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 Centre 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 U.S. 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.

Reprinted from USDA – Agricultural Research Service “1998 Online News Archive of Research”, online at http://www.ars.usda.gov/is/pr/index.html. A full article is also on line at: http://www.ars.usda.gov/is/AR/archive/may98/root0598.htm. For further information, contact Robert F.W. Schroder, ARS Insect Biocontrol Laboratory, Beltsville, MD 20705-2350; phone (301) 504-8369, fax (301) 504-8190, rschrode@asrr.arsusda.gov.

Advances on Aflatoxin Resistance in Corn
The following is a synopsis of two USDA – ARS news releases giving updates on recent advances in the search to reduce potential aflatoxin contamination in U.S. corn.(“New Corn Lines Ward off Aflatoxin” and “New Test for Aflatoxin-Fighting Corn”, both published on the USDA – Agricultural Research Service 1998 Online News Archive of Research, located on the internet at http://www.ars.usda.gov/is/pr/index.html).

Aflatoxin contamination of crops, including corn, peanuts and cotton, by Aspergillus flavus (A. flavus) is a serious problem during droughts. In the U.S., corn with more than 20 parts per billion (ppb) – equivalent to just one ounce in 3,125 tons – of aflatoxin, a carcinogen, is considered unfit for feeding to animals that produce meat or milk for humans. Grain with more than five ppb can’t be used for making food-grade corn products.

Since 1991, Agricultural Research Service plant pathologist Robert Brown and his colleagues in New Orleans have evaluated corn lines from around the world for kernel resistance to A. flavus. In one promising corn line, dubbed GT-MAS:gk, the researchers discovered that the kernels have a thick, waxy coat that inhibits the growth of A. flavus. They’re also trying to identify natural chemicals in the kernel wax that may foil the fungus. Other resistant corn lines they examined have kernels with high levels of a protein called a trypsin inhibitor that keeps A. flavus and other fungi at bay. Also being investigated are the protein’s insecticidal properties against corn earworms, which cause damage that can help virulent fungi gain easier entry to the plant.

Key to the scientists’ research is a fast and easy kernel screening assay, requiring only a few kernels for measuring aflatoxin levels. The assay allows researchers to pinpoint the microbe’s locale or concentration on seeds, and may also help reveal seed regions where resistant mechanisms might be at work.

In closely related research, ARS scientists are employing a new test to quickly identify anti-fungal compounds naturally produced in corn kernels. Chemist Robert A. Norton, located at the National Centre for Agricultural Research Utilization in Peoria, Illinois, has identified a half-dozen promising aflatoxin inhibitors, including alpha carotene and several other carotenoids - compounds that impart yellow color to modern corn hybrids. The new assay is a significant improvement over older, slower testing methods.

Commercial development of A. flavus resistant corn, possible within a few years, could help reduce aflatoxin contamination of the crop.

For further information, contact: Robert Brown, ARS Food and Feed Safety Research Unit, Southern Regional Research Centre, New Orleans, La., phone (504) 286-4359, fax (504) 286-4419, Rbrown@nola.srrc.usda.gov, or Robert A. Norton, USDA-ARS National Centre for Agricultural Utilization Research, 1815 N. University Street, Peoria, IL 61604; phone (309) 681-6251, e-mail nortonra@mail.ncaur.usda.gov.

Editors Note: Aflatoxin contamination has never been detected in Ontario grown corn, believed due to Ontario’s lower ambient temperatures resulting from the surrounding Great Lakes. Regular readers know the Ontario Corn Producers’ Association and the Ontario corn sector are focusing their research efforts to achieve resistance to Fusarium ear molds and the resulting mycotoxins, especially vomitoxin.

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