اثر کشندگی سه حشره کش مختلف روی مرحله تخم، پوره و شفیره سفیدبالک نیشکر، در شرایط آزمایشگاهی

Sugarcane is a strategically important crop that is cultivated in the province of Khuzestan. Sugarcane whitefly, Neomaskellia andropogonis Corbett (Homoptera: Aleyrodidae) is one of the important pests infested sugarcane fields in Ahvaz. In this study, the insecticidal efficacy of deltamethrin, dinotefuran and spiromesifen was evaluated against egg, second instar nymphal and pupal stages of sugarcane whitefly on IRC99-02 variety of sugarcane using a leaf dipping bioassay procedure. The experiments were conducted under laboratory conditions at 30±2°C, 60±5% r.h. and 16:8 h (L: D) photoperiod with nine replications. The insecticides were applied at five concentrations, obtained from previous study, which were 10, 30, 50, 100 and 200 ppm for deltamethrin; 100, 200, 300, 500 and 750 ppm for dinotefuran and 100, 200, 400, 500 and 800 ppm in the case of spiromesifen. For eggs experiment, 30 adults of N. andropogonis were introduced on sugarcane leaves (15 cm length) for 24 h. The number of laid eggs was counted and leaves were dipped for 10s into insecticide solution. Then, the leaves were placed in flat-bottom transparent plastic bottles and after 7 days, the incubation period of N. andropogonis eggs, the number of died eggs were counted. The same procedure was conducted for second instar nymphal and pupal stages; unless for nymphs, 50 nymphs were kept in each sugarcane leaf and the mortality was counted 48 h after exposure to each insecticide. In the case of pupae, the mortality was counted after 6 days. The nymphs and pupae that were dried and detached from the leaf when probed by fine brush were considered dead. Data probit analysis demonstrated that deltamethrin (LC50= 42.5 ppm), and dinotefuran (LC50= 50.9 ppm) were more toxic than spiromesifen (LC50= 148.8 ppm) to eggs of sugarcane whitefly on IRC99-02 variety of sugarcane. However, deltamethrin (LC50= 28.5 ppm) was the most effective insecticide against second instar nymphs followed by spiromesifen (LC50= 256.2 ppm) and dinotefuran (LC50= 418.4 ppm) had the least impact on nymphs. The same results was obtained for whitefly pupae and deltamethrin (LC50= 5.93 ppm) and dinotefuran (LC50= 10.3 ppm) efficiently controlled this stage while spiromesifen (LC50= 79.2 ppm) indicated lower toxicity. The present study suggests that alteration of insecticides could be applicable to the management programs of sugarcane whitefly.