TOXICITY AND PERSISTENCE OF SOME ORGANOPHOSPHOROUS INSECTICIDES AGAINST SAN JOSE SCALE QUADRASPIDIOTUS PERNICIOSUS COMSTOCK*

Abstract

San Jose scale Quadraspidietus perniciosus Comstock continues to be a serious insect pest of apple in Himachal Pradesh. Leaves and twigs become the first target of its attack before the pest moves on to the fruits. When the fruits are harvested, the pest thrives either on leaves or twig;, and a third generation of the pest emerges out during autumn.The attacked leaves and twig; beesorn: spotted, skinny and wither, ultimately affecting the quality of fruits in the following season. Investigations were, therefore, carried out to evaluate the toxicity and persistence of some recommended organophosphorous inszcticides on leaves and twigs of apple when sprayed during autumn as a prophylactic measure.