Differential effects of two plant viruses on performance and biocontrol efficiency of Encarsia formosa fed on Bemisia tabaci

Abstract

The consequences of infection by plant virus on the efficacy of parasitoid wasps are poorly understood. In the current study, an age-stage, two-sex life table and the CONSUME-MSChart computer program were used to test the performance of Encarsia formosa (Hymenoptera: Aphelinidae) on the whitefly, Bemisia tabaci Mediterranean (MED) species, occurring on healthy tomato plants compared to tomato plants infected with Tomato chlorosis virus (ToCV) and Tomato yellow leaf curl virus (TYLCV). The results showed that the intrinsic rate of increase (r) of E. formosa was 0.2051 d−1 on tomato plants infected with only TYLCV. This was similar to the rate on healthy tomato plants, but was significantly higher than the rate on tomato plants infected only with ToCV (0.1965 d−1) and on tomato plants co-infected with both TYLCV and ToCV (0.1772 d−1). Similar differences, consistent with the r values, were found in the net reproduction rate (R0) and finite rate of increase (λ) of E. formosa reared on B. tabaci MED infesting the three different tomato plant/virus combinations. Population growth projection predicted that E. formosa populations would increase faster on B. tabaci MED whiteflies fed on TYLCV-infected tomato plants than that on plants infected with ToCV. Projections of the total mortality rates also predicted that E. formosa were more lethal to B. tabaci MED on TYLCV-infected tomato plants than on ToCV-infected tomato plants. The lowest population growth and mortality potential of E. formosa occurred in B. tabaci MED fed on TYLCV and ToCV co-infected tomato plants. Our findings demonstrate that E. formosa are more effective in controlling B. tabaci on TYLCV-infected tomato plants, than on ToCV-infected and TYLCV and ToCV co-infected tomato plants. The latter two combinations have an apparant negative impact on the survival and parasitization of E. formosa.