1a.Objectives (from AD-416)
Evaluate the potential for permanent establishment of a Moroccan strain of Peristenus relictus in the southern San Joaquin Valley of California by. 1)assessing the incidence of parasitism within a localized population of immatures of the western tarnished plant bug (Lygus hesperus) resulting from inoculative releases of P. relictus, and. 2)documenting the persistence of P. relictus populations following releases.
1b.Approach (from AD-416)
A plot of alfalfa 1-2 acres in area and divided into three sub-plots will be established and managed without insecticides. Alfalfa will be regularly mowed in narrow, alternating strips to maximize survival of lygus nymphs. Parasitoids will be introduced through periodic inoculative releases (once or twice per month) during spring and summer months. During the first two years, population indices for lygus nymphs will be obtained by sampling before initial parasitoid release (early spring) and after the final release (August or September) and the incidence of parasitism will be estimated from the dissection of late-instar nymphs. During the third year of the project, lygus population indices and estimates of parasitism will be obtained periodically (biweekly) throughout the spring and summer months. Overwintering potential and establishment of the parasitoid will be determined based on the incidence of parasitism observed in late-winter or early-spring lygus collections. Documents NFCA with CDFA.
Alfalfa plots were established and managed to facilitate development of high lygus population levels. Population indices of lygus nymphs obtained during alternating weeks from May through early July indicated very high nymph densities. None of the nymphs were parasitized by Peristenus species, indicating the absence of the parasite before releases. Releases of parasites were initiated in early July. Activities during this project were documented through telephone and e-mail correspondence and a site visit by the collaborator. The project was conducted in support of objective 2, “Identify habitat characteristics that impact pest and natural enemy movement and eventual establishment,” of the approved in-house project.