Estimation of yield losses due to sucking pests in transgenic cotton

摘要

Cotton is an important fibre, feed and food crop of global significance cultivated in more than seventy countries. In India, it occupied in 11.6 m ha with a production of 32.5 m bales and productivity of 552 kg lint /ha during 2013-14(www.cotcorp.gov.in). In our country, about 162 insect pest species are found to damage cotton and the monetary value of estimated yield losswas 3,39,660 million annually (Dhaliwal et al, 2010). Sucking insects and bollworms are two important groups causing serious damage to the cotton. Introduction of the Bt cotton is a major milestone in cotton cultivation in India. The major three bollworms, the American bollworm (Helicoverpa armigera), the spotted bollworm (Earias vitella) and the pink bollworm (Pectinophora gossypiella) have attained a non pest status on Bt cotton. On the other hand, the cotton leafhopper Amarasca devastans has become a major production constraint and appearing in serious proportions during the entire crop growth period and can cause seed cotton loss to the extent of 309 kg / ha (Murugesan and Kavitha, 2010). By taking the advantage of nonappearance of bollworms on Bt cotton, the cotton farmers are growing more plants per unit area with excess application of fertilizers with an aim to harvest more seed cotton. Such conditions create a favorable microclimate in the crop canopy for development and growth of sucking pests. Hence, to devise the implementable insect pest management strategies against sucking pests on Bt cotton, it is essential to document the potential yield loss due to sucking pests in Bt cotton. The investigation was therefore undertaken to quantify yield losses due to sucking insect pests in transgenic cotton.