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Hairy Vetch Thwarts Colorado Potato Beetle

By Sharon Durham
April 13, 2000

Colorado potato beetles are deceptively beautiful insects, with five shiny black stripes on a yellow background decorating each wing. But this beetle is notorious for its destructive power. Each year, the Colorado potato beetle and its larvae ravage potato, eggplant and tomato plants.

This pest is also notorious for something else: its ability to develop resistance to insecticides. Because of this, biocontrol becomes a viable option. Biocontrol--the use of one natural organism to control another without chemicals--has an important place in farming systems, including organic farming.

Agricultural Research Service entomologist Kevin Thorpe and collaborators at the University of Maryland have found that an organic mulch made from a cover crop called hairy vetch can reduce Colorado potato beetle damage. They utilized the method developed by ARS plant physiologists Aref Abdul-Baki and John Teasdale, in which hairy vetch is planted in the fall and mowed in the spring before transplanting. The vetch impeded the movement of the beetles, thereby lessening their damage. The vetch, a legume, also added nitrogen to the soil.

In the study, fewer beetles infested tomatoes transplanted into hairy vetch mulch, compared to tomatoes transplanted into black plastic mulch. Yields of staked, fresh-market tomatoes grown in the vetch mulch were comparable to tomatoes treated with insecticides.

The Colorado potato beetle costs U.S. potato, tomato and eggplant growers about $150 million annually in losses and insecticide-related costs. Many growers are using imadacloprid, a new systemic insecticide that provides excellent control. However, unless appropriate measures are taken, resistance will develop. Non-insecticidal methods of control could be useful components of a sustainable, integrated pest management strategy if they can reduce pesticide inputs and slow the rate of resistance.

Thorpe’s next step is investigating the use of organic mulches in larger fields of staked fresh-market tomatoes grown on a commercial scale. This study was undertaken as part of the Sustainable Agriculture program at the Beltsville (Md.) Agricultural Research Center.

Scientific contact: Kevin Thorpe, ARS Insect Biocontrol Laboratory, Beltsville, Md., phone (301) 504-5139, fax (301) 504-5689,