Quarter-inch-long parasitic wasps released in New Hampshire seven years ago are multiplying and spreading to attack tarnished plant bugs. The bugs attack alfalfa, strawberries and other fruits and vegetables.

The female Peristenus digoneutis wasp stings a young plant bug nymph and lays an egg inside the hapless host. A few days later, a wasp larva hatches and begins to eat the nymph from the inside out, killing it in about a week.

In New Hampshire and other northeastern states, tarnished plant bug nymphs and adults attack alfalfa plants. When the alfalfa is cut for hay, the bugs fly off to infest nearby fruit and vegetable crops like strawberries, peaches, apples and beans. The wasp is now killing many plant bugs before they leave the alfalfa. Future studies will determine if the wasps kill plant bugs infesting these other crops.

Entomologists with the Agricultural Research Service in Newark, Del., and colleagues at the University of New Hampshire, Durham, released 3,000 Peristenus wasps into alfalfa fields near the university seven years ago.

UNH workers sampled dozens of fields over several years to collect plant bug nymphs. They sent the samples to the ARS scientists in Newark for analysis--to see if the parasites had survived and deposited eggs in the collected plant bugs. They had. At one farm in the town of Strafford, 35 percent of the tarnished plant bugs were killed by the parasite.

The wasp has now been found in six of New Hampshire’s 10 counties. It has survived as far north as the Canadian border near Lake Champlain in New York.

Scientific contact: William H. Day, ARS Beneficial Insects Research Laboratory, Newark, DE 19713; phone (302) 731-7330, fax (302) 737-6780, tropp@udel.edu; Alan T. Eaton, Plant Biology Department, University of New Hampshire, Durham, NH, phone (603) 862-1734, fax (603) 862-1713, alan.eaton@unh.edu