Susceptibility of brown planthopper (BPH) and green leafhopper (GLH) to insecticides under different temperatures.

Abstract

The effect of 6 different temperatures (18, 21, 24, 27, 30 and 33°C) on the LD50s of 7 insecticides (BPMC [fenobucarb], carbaryl, carbofuran, cypermethrin, deltamethrin, diazinon and malathion) to the brown planthopper [Nilaparvata lugens] and green leafhopper [Nephotettix virescens] was studied in the laboratory. Adults were treated topically and provided with 2-week-old rice seedlings as food. The pests were most susceptible to the pyrethroids at lower temperatures and to the other insecticides at higher temperatures. Against Nilaparvata lugens, all insecticides except the 2 pyrethroids had lower LD50s at 33 than at 18°C. Against Nephotettix virescens, all the insecticides except carbaryl and the pyrethroids were more potent at higher temperatures. Insecticidal activity was similar in the range 27-30°C.