Evaluation of susceptibility of the first instar nymphs and adults of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) to neonicotinoid insecticides under laboratory conditions

The greenhouse whitefly, Trialeurodes vaporariorum (Westwood), has been well established in the greenhouse ecosystems and is one of the most important pests on various greenhouse crops worldwide. Because of its high fecundity and resistance to commonly used pesticides, a study was conducted to examine the effectiveness of conventional insecticides of neonicotinoid compounds. In this study, the whiteflies on the ornamental plant genus Gerbera were collected from a greenhouse in the city of Mahalat and reared on tobacco under laboratory conditions at 25 ± 2ºC and 60 ± 5% Rate of humidity (RH) and a photoperiod of 16: 8 h (L: D). The toxicity of three neonicotinoid insecticides including imidacloprid SC35% (Confidor), thiamethoxam SC21.6% (Actara) and dinotefuran SG20% (Starkle) on the adults and first instar nymphs of T. vaporariorum, was evaluated using leaf dipping bioassay method. The susceptibility of adults was assessed at 24 hour post-treatment. The LC50 values of imidacloprid, thiamethoxam and dinotefuran for adults were 130.48, 52.89 and 93.55 ppm (a. i.) respectively. The mortality of immature stages was assessed at 72 hour post-treatment. The LC50 values of imidacloprid, thiamethoxam and dinotefuran for the first instar nymph were 26.65, 12.62 and 15.48 ppm (a. i.) respectively. The results suggest that all insecticides are more toxic on first instar nymphs than adults while thiamethoxam has the highest toxicity. The insecticides dinotefuran and imidacloprid can effectively control the adults and first instar nymphs as well.