Sublethal effects of thiocyclam hydrogen oxalate and spiromesifen, on life history and population growth of Encarsia formosa (Hymenoptera: Aphelinidae)

Encarsia formosa Gahan (Hymenoptera: Aphelinidae) is one of the most important endoparasitoids of the greenhouse whitefly, Trialeurodes vaporariorum, westwood (Hemiptera: Aleyrodidae). In this study, we investigated the sub-lethal effects (LC25) of two insecticides, thiocyclam hydrogen oxalate and spiromsifen, on the life table and population growth parameters of E. formosa under laboratory conditions. Bioassays were conducted by dipping bean leaves containing parasitized third instar nymphs of T. vaporariorum in the obtained LC25 concentrations of the two insecticides. The life table data were analyzed using the computer program TWOSEX–MSChart based on the age-stage, two-sex life table theory. The results showed that the shortest pre-adult period and the lowest survival rate were recorded in the F1 generation of parasitoides exposed to spiromsifen. Additionally, both thiocyclam hydrogen oxalate and spiromesifen reduced adult longevity, fecundity rate and reproductive days compared to the control group. However, using of sub-lethal concentration of spiromesifen negatively affeted on the population growth parameters (R0, r, and λ) of E. formosa, while thiocyclam hydrogen oxalate had no side effects on these parameters. The findings of this research suggest that thiocyclam hydrogen oxalate has the less harmful effect compared to spiromesifen on E. formosa, likely due to the biorational properties. This makes thiocyclam hydrogen oxalate a promising option for the management of T. vaporariorum. It would be better to evaluate complementary experiments in terms of its side effects against other natural enemis of greenhouse whitefly under greenhouse conditions.