Evaluation of Orius majusculus and O-laevigatus as predators of Bemisa tabaci and estimation of their prey preference

The polyphagous predators Orius laevigatus and O. majusculus are common in several vegetable crops and are well-known biocontrol agents of thrips. The whitefly Bemisia tabaci is an important pest for some of these crops. The aim of the present study was to examine the potential of O. laevigatus and O. majusculus as biocontrol agents for B. tabaci when this whitefly coexists in a crop with the thrips Frankliniella occidentalis. Laboratory experiments were conducted to determine (1) the whitefly developmental stages accepted as prey by adults and nymphs of both Orius species, (2) the duration of the post-embryonic period when the only prey available were whitefly nymphs and (3) the preference of 0. laevigatus and 0. majusculus nymphs and adults for either B. tabaci or F occidentalis. The results presented in this paper show that both 0. laevigatus and 0. majusculus are able to feed on whitefly eggs, nymphs and adults and that they can complete their respective preimaginal development with R tabaci nymphs as their only available prey. When these predators were simultaneously presented with a choice of thrips larvae, whitefly eggs, whitefly nymphs and whitefly adults both species showed a clear preference for F occidentalis, but at the end of the experiment 0. majusculus adults have also killed up to 59% of the whitefly present. These results suggest than this Orius species could serve as an important biological control agent for use in crops in which B. tabaci and F occidentalis occur together. (c) 2007 Elsevier Inc. All rights reserved.