Abstract: Small Group Session - Tarnished Plant Bug

Current Status of Biological Control of the Tarnished Plant Bug in Northeast Alfalfa and Research on Extension of This Method to Other Crops

Bill Day, an entomologist from Delaware, has been involved in establishing Peristenus digoneutis, a parasitic wasp from Europe that attacks the tarnished plant bug, Lygus lineolaris, as a small nymph and kills it before it can reproduce. The parasitoid has spread north and east from New Jersey far into New England. In alfalfa, it has reduced tarnished plant bug densities by up to 75%. Research on the effect of this parasitoid on tarnished plant bug in strawberries is just beginning.

Tarnished Plant Bug

Jake Guest, an organic farmer from Vermont, has found that economic damage from tarnished plant bug in vegetables and strawberries may be much greater than previously assumed. This bug, which has several generations per year, causes blossom abortion in peppers and eggplant, deformation of growing tips in celery and spinach, and cosmetic damage to marketable parts of broccoli and lettuce, as well as deformation (‘cat-facing’) of strawberries. Efforts to find alternatives to chemical control have so far been unsuccessful in Vermont.

Discussion: Tarnished Plant Bug

Bill Day explained how the U.S. Department of Agriculture does classical biological control, identifying the natural enemies in other countries of insects that are pests here, then bringing in the natural enemies and establishing them permanently. Then, he described the current state of knowledge about Peristenus digoneutis and the effect it is having on the tarnished plant bug in various crops. P. digoneutis has two generations per year and then spends the winter as a cocoon in the soil, so it may need habitat that is not sprayed during the key periods and not tilled during overwintering in order to thrive.

Jake Guest described efforts he and other Vermont growers had made to control tarnished plant bug. Botanical insecticides were generally ineffective. Row covers worked in strawberries, but were labor-intensive. Another parasite of tarnished plant bug, Anaphes iole, is commercially available, but expensive, and timing the releases is difficult. Some farmers have used clovers as trap crops to draw the bugs away from strawberries. Jake avoids the use of clover as a cover crop, and takes care to manage weeds that are hosts to tarnished plant bug, especially red-root pigweed. The Vermont vegetable and berry growers funded research on fungi pathogenic to the tarnished plant bug, but the fungi identified have not yet been tested in the field.