STATUS OF INSECTICIDE RESISTANCE IN LEAFHOPPER , AMRASCA BIGUTTULA BIGUTTULA ( ISHIDA ) ON COTTON

Cotton is one of the most important cash crops of India. It is grown for its lint and seed. In India, cotton was cultivated on an area of 11.70 million ha with a production of 29.00 million bales of seed cotton during 2013-14. Average productivity of cotton in India is 540 kg lint per ha, which is low when compared to world average of 766 kg lint per ha (AICCIP, 2013-14). The major limiting factor in its production is damage due to insect pests. After the introduction of Bt cotton, there was a check to the bollworm complex, but the sucking pest population increased gradually reaching economic injury level in many parts of India (Mohan and Nandini, 2011). Among the sucking pests, the cotton leafhopper, A. biguttula biguttula, is an important sucking pest causing both quantitative and qualitative losses. Though it is an early phase pest, it occurs all throughout the season serving as one of the limiting factors in crop production. Cotton leafhopper nymphs as well as adults suck sap from the leaves and damages the phloem tubes causing the distortion of leaves resulting into a condition known as ‘hopper burn’. Severe infestation on cotton results in shedding of leaves, squares and young bolls which leads to significant yield losses (Narayanan and Singh, 1994, Memon and Chang, 2005). Inspite of repeated use of insecticides, it is becoming difficult to manage this pest. Though control failure may be due to many factors, one of the major factors is the development of resistance to insecticides (Jeya Pradeepa and Regupathy, 2002). The indiscriminate use of insecticides has resulted in the development of resistance in insects to insecticides and resurgence of sucking pests (Rohini et al. 2012). Insecticide resistance is the development of an ability in a strain of insects to tolerate doses of toxicant which would prove lethal to majority of individuals in a normal population of same species. This pest was found to have developed resistance to various insecticides viz., malathion, dimethoate, oxydemeton methyl and phosphamidon (Singh and Jaglan, 2005). Resistance in leafhopper population against organophosphates has also been reported by Sagar et al. (2013). Although various insecticides have been recommended for the control of the pest but the pest problem is aggravated due to control failures in many areas in Punjab (Dhawan and Simwat, 2002). Newer insecticides belonging to neonicotinoid group viz., imidacloprid, thiamethoxam and acetamiprid have been introduced which were found to be quite effective at very low doses and are relatively safer than conventional systemic insecticides (Chalam et al., 2003). Neonicotinoids have historically given very good control of leafhopper, in recent past, field level failure of neonicotinoids was noticed in the leafhopper population of Andhra Pradesh (AICCIP, 2008-09). As neonicotinoids along with other insecticides have been recommended in Punjab to control sucking pests of cotton, there was a need to assess the level of resistance developed by this pest against these insecticides. Keeping this in view, present studies were planned to know the status of insecticide resistance and to determine the relative toxicity of different insecticides against this pest.