Distinguishing Species of Beneficial Wasps Made Easier, Faster

For the first time, scientists have developed an easier, faster way to identify tiny beneficial wasps that control key crop pests in the United States.

Cornell University scientists, in collaboration with Agricultural Research Service researchers at the Beneficial Insects Introduction Research Laboratory, Newark, Del., devised a genetic technique that identifies the larvae of several parasitic wasp species. Previously, scientists had to rear the parasites to their adult stage, a process that took months.

So far, the new method identifies two European parasites: Peristenus digoneutis, a quarter-inch-long wasp that attacks the tarnished plant bug, Lygus lineolaris, a pest of many crops; and P. conradi, which attacks the alfalfa plant bug, Adelphocoris lineolatus. The Newark lab permanently established both parasites and determined they were spreading in the Northeastern United States.

Female Peristenus wasps sting young plant bug nymphs, laying a tiny egg in them. A few days later, a wasp larva hatches and begins to eat the nymph.

The new method amplifies genetic material unique to the wasp during its early larval stage. It also detects pest insects that contain parasitic larvae, reducing the need for a skilled dissector to measure parasitism inside the insect pests.

The tarnished plant bug and its western cousin are important pests of crops grown for seed, vegetables, fruits, cotton and seedling trees throughout the United States. They suck the sap from flowers, young fruits, seeds and plant buds. Annually, they cause tens of millions of dollars in losses and control costs.

Successful biological controls are less costly than chemicals for controlling pests that seriously reduce the quantity and quality of crops, and are much less likely to cause environmental problems.

The new technique will also distinguish a native wasp parasite (P. pallipes) from the two introduced species. The scientists are now determining whether other related parasite species can also be identified with the new technique. ARS is the chief research agency of the U.S. Department of Agriculture.

Scientific contact: William H. Day, ARS Beneficial Insects Introduction Research Laboratory, Newark, Del.; phone (302) 731-7330, ext. 24, fax (302) 737-6780, wday@biir.ars.usda.gov.