Effect of Sub-lethal Doses of Three Insecticides on the Reproductive Rate of the Brown Planthopper, Nilaparvata lugens1, on Rice

LD5, 10, 25, and 50 values of the insecticides methyl parathion, decamethrin, and Perthane were estimated for the 5th instar nymphs of N. lugens. LD values were lowest for decamethrin, followed by Perthane and methyl parathion. Topical applications of sub-lethal doses of methyl parathion and decamethrin on 5th instar nymphs caused increases in reproduction in the resulting adults. Highest reproductive stimulation occurred at the LD dosage for methyl parathion and at LD 50 for decamethrin. Perthane did not cause reproductive stimulation at any of the four dosages tested.