2011 Annual Report
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.
Alfalfa plots were maintained for a third and final summer to facilitate development of high lygus population levels. Assays of field-collected Lygus nymphs in the fall of 2010 and spring of 2011 again failed to detect parasitism by released Peristenus. Population indices of lygus nymphs obtained during spring and summer of 2011 indicated high nymph population densities. Multiple releases of parasites into the field were accomplished during the spring and summer, and two of these releases were augmented by caging Peristenus over lygus nymph-infested alfalfa. Activities during this project were documented through telephone and e-mail correspondence and a site visit by the collaborator. The goal of the project is to establish Peristenus relictus as a natural enemy of lygus bugs attacking cotton and other crops, which is in support of Objective 6 of the approved in-house project.