Persistence of toxicity of some insecticides against the neonate larvae of Leucinodes orbonalis Guen.

Persistent toxicity of nine insecticides, viz, fenitrothion, methyl parathion, malathion, endosulfan, monocrotophos, quinalphos, phosphamidon, carbarfl and dimethoate was evaluated against the neonate larvae of Leucinodes orbonalis Guen. Amongst these insecticides, the residues of malathion, quinalphos and dimethoate were found to have the quickest knock-down Meet till four days as evidenced by LT50 values, being 3.33, 3.35 and 3.97 days, respectively. Tbe residues of methyl parathion, endosulfan, monocrotophos and phosphamidon took six days to effect the same mortality of the brinjal shoot and fruit borer. The persistent toxicity (PT)of phosphamidon was the highest while malathion proved to be the led persistent insecticide.