Use of barriers to limit movement of parasitoids of Lygus spp.

Alfalfa plots enclosed by 1.9 m high plastic barriers limited the movement of Lygus spp, parasitoids released inside the enclosures. Leiophron uniform is (Gahan), a parasitoid of Lygus spp, nymphs, was successfully contained i nside the enclosures. Parasitism of nymphs inside the enclosures was betwee n 20 - 29% with levels of only 0 - 5.6% outside, and 0 - 0.3% inside enclos ures without parasitoid releases. Some Anaphes iole (Girault) moved over th e barriers, but parasitism of Lygus spp. eggs averaged 43% inside release e nclosures, 20 - 21% outside, and 13% inside enclosures without parasitoid r eleases.