Relative Susceptibility of Tea Mosquito Bug, Helopeltis Theivora Waterhouse and Red Spider Mite, Oligonychus Coffeae Nietner Eggs to Commonly Used Pesticides

The tea mosquito bug (Helopeltis theivora Waterhouse) and red spider mite (Oligonychus coffeae Nietner) are the two major pests of tea (Camellia sinensis L.).Their intensity of infestation was increasing day by day in an alarming proportion and increasing resistance to pesticides constitutes a serious problem in North Bengal tea plantations, India.One of the insecticide resistance management strategies is the use of chemicals that can effectively control the pest in the initial life stage (egg stage).However most of the earlier studies were done to control the mobile stages of H. theivora and O. coffeae.The present experiment was conducted to evaluate the effectiveness of acaricides/insecticides in killing its eggs.On the basis of LC 50 values, the descending order of ovicidal toxicity of different commonly used insecticides to H. theivora eggs were: etofenprox, β-cyfluthrin, cypermethrin, imidacloprid, fenpropathrin, λ-cyhalothrin, deltamethrin, profenofos, monocrotophos, thiomethoxam, alphamethrin, dimethoate, quinalphos, chlorpyriphos, oxydemeton methyl, acephate, azadirachtin and endosulfan.In case of O. coffeae eggs the lowest LC 50 value was determined for fenazaquin, which was followed by profenophos, propargite, fenpropathrin, ethion, dicofol, abamectin and finally by azadirachtin.The data obtained in the present study may be used as a tool of IRM (integrated resistance management) strategies that can effectively control the pests in the initial stage itself (egg stage).