“Chefs” Cooking Up Trouble for Colorado Potato Beetle

A team of USDA entomologists-turned-chefs are cooking up trouble for the Colorado potato beetle in ways that will cut the need for chemical insecticides against the crop pest.

The scientists are developing an artificial diet to feed massive numbers of lab-raised Edovumputtleri, parasitic wasps that attack Colorado potato beetles. The research team’s culinary pursuits are part of a two-year project to streamline an efficient wasp-rearing process for commercial insectaries. This could further Edovum’s prospects of becoming a viable alternative to some beetle-killing insecticides growers now use.

Female Edovum wasps lay their eggs inside the eggs of Colorado potato beetles. This prevents the beetle’s offspring from hatching and chewing plant parts. The wasps also suck juices from some of the beetle eggs they don’t use as a nest for their own eggs.

The artificial diet mimics the beetle eggs’ contents by combining chicken egg yolk, powdered milk and insect blood called hemolymph. The entomologists’ “kitchen” is the Insect Biocontrol Laboratory operated in Beltsville, Md., by USDA’s Agricultural Research Service. There, the scientists also devised artificial egg membranes to house Edovum’s brood as they feed and grow on the brew.

The key is finding cheap, off-the-shelf substitutes for hemolymph. It harbors critical substances that trigger the wasp larvae’s metamorphosis into adult insects. As it now stands, the larvae must be reared on beetle eggs. These are harvested from a lab colony of adult insects grown on thousands of potato plants.

The Beltsville work follows earlier studies by scientists at Rutgers University and the New Jersey Department of Agriculture’s Bureau of Biological Pest Control. Those studies explored Edovum’s potential to reduce, rather than replace, the use of insecticides that can endanger helpful predatory bugs and leave behind chemical residues. In field trials with eggplant, researchers released 2,000 wasps per acre each week for about eight weeks. As a result, growers only had to spray chemicals four times during the growing season, down from the average 14 treatments.

Scientific contacts: Dale Gelman and Jing S. Hu, ARS Insect Biocontrol Laboratory, Beltsville, Md., phone (301) 504-8909, fax 504-5104, gelman@asrr.arsusda.gov.