Comparative efficacy of some botanicals, bio-pesticides and insecticides against onion thrrips, Thrips tabaci Lindeman

摘要

Onion (Allium cepa L.) is an important vegetable crop in India. It is relished mostly as salad and Indian cuisine is incomplete without onion. India is the second largest onion producing country in the world with approximately 7.6 lakh ha area with anannual production of 12.20 lakh MT during 2009-10 (Anonymous, 2010). Thrips {Thrips tabaci Lindeman) is a regular and potential pest of onion and cau.se as high as 90 per cent of yield loss (Gupta el al., 1984; Dharmasena, 1998; Sudherma and Nair, 1999). Thrips attack onion at all the stages of crop growth, but their count increases from bulb initiation and remain high up to bulb development and maturity. Both nymphs and adults cause damage directly through feeding and indirectly through the transmission of lethal plant viruses. It is difficult to control this pest with insecticides because of its small size and cryptic habits (Lewis, 1997). Failure to control this pest causes considerable damage and results in immense economic losses by remarkably reducing yield (Anonymous, 2000). Farmers are extensively and using different types of insecticides for controlling the pest. However, repeated applications of chemicals is not a desirable practice, as this could lead to undesirable resistance problems. Toavoid further resistance in this pest, different non cheinical methods were evaluated. Use of natural plant products or plant-based insecticides has been found to be effective in controlling the insect pests in many vegetable crops (Gupta et al., 2002;Udainyan, 1994; Devi et al., 2003 and Bhandari, 2003). Vestergaard et al. (1995) and Brownbridge (1995) showed that B. bassiana, M. anisopliae and V. lecanii were more active against the Western flower thrips, Frankliniella occidentalis. The present study was carried out to test the efficacy of botanicals and biopesticides in comparison with the recommended insecticides for the management of thrips in onion.