Pest Records on Transgenic Cotton in the Marathwada Region

Survey of rainfed cotton growing areas of Marathwada region during 2006–07 and 2007–08 revealed that incidence of various pests e.g., bacterial blight, grey mildew, Alternaria blight, root rot, wilt, reddening, and mealybugs is on rise on different transgenic cotton lines. Bacterial blight and greymildew diseases are causing significant yield losses and on the verge of epidemics. Grey mildew, that used to appear at harvesting stage could be seen affecting young as well as at vegetative stage. Survey indicates wide occurrence of bacterial blight, grey mildew and Alternaria blight with higher intensity (33.5%; 19.7% and 14.9%), respectively on Bt than their non-Bt conterpart in all the districts. Though Bt has provided relief from Helicoverpa, another insect pest, mealybug has now emerged as key insect pest causing yield losses. Irrespective of cultivars it is the most prevalent pest in its occurrence in the surveyed region. The farmers are suffering huge losses in terms of yield as well as increased cost of production. Maximum severity was observed in Parbhani with 41.0% leaf infestation and 35.8% green boll damage. Lowest incidence was recorded in Hingoli district with 11.4% leaf infestation and 10.1% green boll damage. Like Helicoverpa mealybug is also polyphagous and found infesting weeds especially Parthenium, Xanthium strumarium, Psorolia spp, wild okra, vegetable and ornamental crops growing in the cotton ecosystem. If left unchecked mealybug incidence is capable of undoing all benefits incurred due to Bt in terms of increased yield and reduction in use of chemical pesticides in Marathwada and other cotton growing areas.