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Caterpillar Pests Beware: New Fungal Strain is Out to Get You

The discovery of beneficial fungi that produce mycoinsecticides brightens the future of environmentally friendly controls for insect crop pests, Agricultural Research Service scientists report.

Mycoinsecticides are fungal sprays. When applied to insect-infested plants, fungal spores attack the pests by penetrating their outer cuticle. Then the fungus eats them from the inside out. Spores from dead insects can survive to reinfect subsequent pest generations.

For example, one new strain of the Beauveria bassiana fungus--known as BB-1200-- appears to be more effective in curbing caterpillar pests than its close relative, the commercially available GHA strain.

Long-standing collaborations between ARS scientists at the U.S. Plant, Soil and Nutrition Laboratory, Ithaca, N.Y., and Mycotech Corp., Butte, Mont., led to the discovery that spores of Beauveria strain GHA can control many important insect pests of agricultural crops like cabbage, broccoli, cucumber and greenhouse ornamentals. This discovery led to developing the commercial products Mycotrol and BotaniGard, which have been registered for use in the United States, Mexico, and other counties for biological control of grasshoppers, whiteflies, aphids, thrips and diamondback moths.

After GHA’s discovery, the search intensified for a more virulent, broad-spectrum mycoinsecticide effective against a large group of lepidopteran (caterpillar) pests. In June 1999, scientists in ARS’ fungal-screening program at Ithaca discovered the high virulence and exceptionally broad lepidopteran host range of the new Beauveria BB-1200 strain, originally taken from a diamondback moth.

Laboratory bioassays showed BB-1200 consistently exhibited virulence equal to or greater than the GHA strain against all lepidopteran pests tested. Included were fall armyworm, beet armyworm, black cutworm, corn borer and cabbage looper--pests not highly susceptible to GHA. These lepidopteran defoliators are among the most destructive pests of important crops like corn and cabbage, costing several billion dollars in losses each year.

For more details, see the November 2000 issue of Agricultural Research magazine.

ARS is the chief scientific research arm of the U.S. Department of Agriculture.

Scientific contact: Stephen P. Wraight, ARS U.S. Plant, Soil, and Nutrition Laboratory, Ithaca, N.Y., phone (607) 255-2458, fax (607) 255-1132, [email protected].