The sublethal effects of thiamethoxam-lambda cyhalothrin on the population growth performance of greenhouse whitefly, Trialeurodes vaporariorum, and its parasitoid, Encarsia formosa, under laboratory conditions

Abstract

The greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), is one of the most important pests of vegetables and ornamental plants. In this research, the effects of sub-lethal concentration (LC30) of thiamethoxam-lambda cyhalothrin (TLC) on the biological properties, life table parameters and population projection of T. vaporarium and its parasitoid, Encarsia formosa, Gahan were studied at controlled conditions (25 ±2 ℃, R.H. 60 ±10 % and a photoperiod of 16:8 h (L:D). Bioassays were conducted by dipping tomato leaves containing third-instar nymphs of the greenhouse whitefly in the obtained LC30 concentration of TLC. 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 sublethal concentration of the above-mentioned insecticide had an impact on the population growth of greenhouse whiteflies by shortening their development time and adult lifespan, reducing their fecundity. The LC30 concentration of TLC had also negative effects on the life history and life table parameters of E. formosa. The results illustrated that the sublethal concentration of TLC resulted in prolonged developmental time, decreased adult longevity, survival rate, and population growth parameters of E. formosa. The population projection results were in accordance with the population growth parameters of the greenhouse whitefly and E. formosa. We concluded that TLC should not be used in integrated pest management programs where E. formosa exists.

Keywords

• greenhouse pest
• parasitoid wasp
• neonicotinoide
• pyrethroid
• population dynamics