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Brighteners Shine Light on Control of Diamondback Moth

A possible new aid to beating back diamondback moths is being tested by Agricultural Research Service scientists. The diamondback moth is a world-wide pest of cruciferous crops such as cabbage, turnip and broccoli, and causes about $1 billion a year in crop losses and pest control costs.

The scientists are using naturally occurring viruses as a new approach for helping to control these pests. But the viruses act slowly, and the moth caterpillar can inflict a great deal of damage before it dies.

Fluorescent brighteners, when used with moth-infecting viruses, can enhance the potency of the virus. Fluorescent brighteners are chemicals that take in ultraviolet light and re-emit the energy as visible light. They are commonly used in laundry detergents to make clothes seem brighter.

Research entomologists Martin Shapiro and Robert Farrar of ARS' Insect Biocontrol Laboratory in Beltsville, Md., have been testing a newly discovered nucleopolyhedrovirus of diamondback moth. They found the addition of certain fluorescent brighteners can make the virus more effective against the insect. The new virus was discovered by A.H. McIntosh and C.W. Kariuki of ARS' Biological Control of Insects Research Laboratory in Columbia, Mo.

The nucleopolyhedroviruses (NPVs) now under study are naturally occurring viruses, each of which infects only a few insect species. The viruses are promising alternatives to pesticides for many important pests, especially caterpillars. While some NPVs have been known to infect the diamondback moth, none was particularly potent against it. In lab tests, the fluorescent brightener made the virus four times more effective against the moth caterpillars.

Non-chemical controls are increasingly important because many insects, including the diamondback moth, are becoming resistant to many chemical and microbial insecticides.

Alternative control tactics, such as naturally occurring viruses, can reduce the use of chemical pesticides and problems of contamination, insecticide resistance, worker exposure and residues in food.

ARS is the U.S. Department of Agriculture's chief scientific research agency.