Interspecific competition between Peristenus spretus and Peristenus relictus (Hymenoptera: Braconidae), larval parasitoids of Apolygus lucorum (Hemiptera:Miridae)

In this study, interspecific competition between larvae of P. spretus and P. relictus for the nutrients inside their common host, the green plant bug (Apolygus lucorum Meyer-Dürin), as well as their extrinsic competition for host resources were investigated in the laboratory. We examined the effect of four different time intervals between oviposition by the two species (10 min, 24 h, 48 h, and 72 h) and two parasitoid sequences (i.e., P. spretus before P. relictus [Ps-Pr] and P. relictus before P. spretus (Pr-Ps)] in no-choice tests to measure nutrient competition between the two species. In choice tests, three densities of A. lucorum nymphs (40, 80, and 120) were presented to various combinations of P. spretus and P. relictus (1,1; 2,2; or 3,3 pairs). In addition, the developmental times of the immature stage (from egg to late instar larva) of P. spretus and P. relictus were determined. We found that neither the time interval between oviposition by the two competing species, nor the order the parasitoids attacked (Ps-Pr or Pr-Ps) had any influence on the percentage of parasitoid offspring that belonged a particular parasitoid species. Peristenus spretus dominated, accounting for 89.2-97.9% of parasitoid offspring in the no-choice nutrient competition experiment. Parasitoid sequence did, however, affect sex ratio in the dominant parasitoid’s offspring, with 48.2% of P. spretus offspring being female in the Pr-Ps sequence, while only 29.2% were female in the Ps-Pr sequence....
Source: Biological Control - Category: Biology Source Type: research