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Beetles Learn that "You Are What You Eat"

By Sharon Durham
March 12, 2004

Agricultural Research Service scientists studying the Colorado potato beetle (CPB) with the goal of finding an effective biological control against the pest have been hampered by the insect's reluctance to eat a formulated diet. Now ARS scientists in Beltsville, Md., have developed a freeze-dried diet palatable to CPB.

Previously, the agency's Insect Biocontrol Laboratory in Beltsville had developed a palatable diet for the destructive beetle, but the diet had to be prepared immediately before feeding or the picky insect pest wouldn't eat it.

To get around the problem, microbiologist Phyllis Martin and her colleagues employed freeze-drying--commonly used to make instant coffee and packaged food for astronauts--to preserve the diet after preparation. Martin found the beetles readily eat a freeze-dried diet that has been moistened with water or a suspension of bacteria. The freeze-dried diet is convenient because it allows for long-term storage, estimated to be at least nine months.

The freeze-dried diet also has other benefits. Some toxins being considered for control of CPB are heat-sensitive, which eliminated them from testing with the previously formulated ARS diet that had to be prepared with boiling water.

Controlling CPB is vitally important to commercial growers. Both immature and adult beetles feed on potato, eggplant and tomato vegetation, and have developed resistance to most available insecticides. Researchers are looking for alternative methods, such as bacteria or fungi that only harm target pest insects such as CPB.

The freeze-dried diet seems to allow concentrated ingestion of the bacteria meant to control CPB and will provide the means for testing a wider range of bacterial and fungal controls.

More information about the research is in the March issue of Agricultural Research magazine.

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