Interspecific interference competition between Encarsia formosa and Encarsia sophia (Hymenoptera: Aphelinidae) in parasitizing Bemisia tabaci (Hemiptera: Aleyrodidae) on five tomato varieties

Abstract Interspecific competition between Encarsia formosa and Encarsia sophia, two major parasitoids of Bemisia tabaci, and the influence of five tomato varieties on competition outcome were investigated under laboratory conditions. E. formosa parasitized more B. tabaci than E. sophia when in single wasp assays on any of the tomato varieties investigated. When B. tabaci nymphs were exposed to both wasp species (either simultaneously or sequentially), the number of B. tabaci nymphs parasitized by either wasp species was significantly decreased compared to the sole access condition. Total mortality of B. tabaci was increased when B. tabaci nymphs were exposed to both wasp species compared to only one wasp species. Thus competition between E. formosa and E. sophia apparently reduced parasitoid offspring numbers, but not the efficiency of biological control. In fact, control efficiency was enhanced in some cases, particularly on tomato variety Huangtuoyuan (HTY). When wasps were allowed sequential access to hosts, interference occurred through host feeding by the second wasp, especially if it was E. sophia. The effect of different tomato varieties was not significant.