STUDIES ON WATERMELON THRIPS, Thrips palmi KARNY (THYSANOPTERA: THRIPIDAE)
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Date
2014-07
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University of Horticultural Sciences, Bagalkot
Abstract
Study was carried out during 2013-14 at College of Horticulture, Bagalkot, University of Horticultural Sciences, Bagalkot. Survey was carried out during 2013-14 to study the thrips species composition and extent of thrips infestation and watermelon bud necrosis viral (WBNV) disease incidence on watermelon in different localities of Karnataka viz., Bagalkot, Belgaum, Kolar and Mysore. The results revealed that the major thrips species consisted of Thrips palmi Karny and Thrips sp. Among these two species, Thrips palmi was more abundantly occurred on watermelon fields of all four localities surveyed. The thrips infestation and WBNV disease incidence in unsprayed watermelon fields ranged from 2.02 to 4.94 thrips per plant and 75.44 to 92.08 per cent disease incidence, respectively. Among the different localities surveyed the watermelon fields at Mysore recorded lowest thrips infestation and WBNV disease incidence (2.02±0.16 thrips/plant and 75.44 % disease incidence, respectively) as compared to the fields from Bagalkot, Belgaum and Kolar (4.94±0.24 thrips/plant and 92.08% disease incidence, 3.80±0.20 thrips/plant and 79.28 % disease incidence and 4.76±0.22 thrips/plant and 91.68% disease incidence, respectively). Study on the level of thrips infestation over a crop growth period indicated that the thrips infestation started appearing only around 35 days after sowing and it was lowest during vegetative stage of the crop. The infestation started to build up gradually as the crop stage advanced and reached its peak at 60 days after sowing which coincided with fruiting stage. Thereafter, the thrips infestation started to decline gradually. Significantly lesser level of thrips infestation (1.80±0.19 thrips/plant) and WBNV disease incidence (70.00±3.96%) was observed in the case of watermelon with silver colour UV reflective polyethylene mulch compared to watermelon without polyethylene mulch (6.30±0.86 thrips/plant and 94.00±0.85%, respectively). Management practices involving use of silver colour UV reflective mulch, seed treatment with imidacloprid 45 FS at 10 ml per kg seeds followed by foliar application of acephate 70 SP at 1 g per liter of water found to be most effective in managing thrips and WBNV disease incidence on watermelon.
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