Toxic Effects of Two Insecticides on Brown Plant Hopper, Nilaparvata lugens and its Predators Micraspis discolor and Lycosa pseudoannulata

摘要

The experiment was conducted in the net house and laboratory to determine the effectiveness of two insecticides viz., Cymbush (Cypermethrin) and Brifer (Carbofuran) on brown plant hopper, Nilaparvata lugens and the toxic action of these insecticides to the predators lady bird beetle, Micraspis discolor and wolf spider, Lycosa pseudoannulata. Effectiveness of the insecticides was assessed on the basis of percentage of corrected mortality of brown plant hopper, lady bird beetle and wolf spider under laboratory condition at 24, 48 and 72 h after treatment. Cymbush 10EC @ 0.05 kg a.i. ha-1. caused 100% mortality of insect populations at different time intervals. All the doses of Brifer 5G caused a good mortality of N lugens at different time intervals and was effective at higher dose. Cymbush 10EC @ 0.04 kg a. i. ha-1. and Brifer 5G @ 0.5 kg a.i. ha-1. were found very effective against N. lugens. The effectiveness of Cymbush 10EC decreased and Brifer 5G increased with increasing time interval. Cymbush 10EC @ 0.05 kg a.i. ha-1. was highly toxic and 0.01 kg a.i. ha-1. was less toxic to both the predators. Brifer 5G @ 0.5 kg a.i. ha-1. was least toxic to the predators. Between the two predators L. pseudoannulata was more susceptible to the insecticides than M. discolor .