Scientific Officer, Spices Research Centre, Bgangladesh Agricultual Research Institute, Shibganj, Bogra, Bangladesh.
Additional Agriculture officer, Rangpur Sadar, Rangpur, Bangladesh.
Senior Assistant Director, National Agriculture Training Academy (NATA), Gazipur, Bangladesh.
Scientific Officer, Regional Horticulture Research Station, lebukhali, Patuakhali, Bangladesh.
Scientific Officer, BINA, Mymensingh, Bangladesh.
The field experiment was conducted at Spices Research Centre, Shibganj, Bogra, Bangladesh during Rabi season of 2016-17 to evaluate the efficacy of different bio-rational insecticides for the management of thrips of onion. Six treatments were replicated three times in randomized complete block design. The treatments were T1= Spraying of Beauveria bassiana @ 5g/litre of water; T2= Spraying of Metarhizium anisopliae @ 4g/litre of water; T3= Spraying of Spinosad (Success 2.5 SC) @ 1.2ml/litre of water; T4= Farmers practice- Three spraying of Dimethoate (Tafgor 40EC) @ 1ml/litre of water; T5= Control (Water +Sticker i.e Trix @ 5ml/litre of water) and T6= Absolute control. All the insecticides were significantly better than absolute control in reducing thrips population after every spray. It was evident from the study that significantly lowest (4.30 thrips/plant) thrips populations were recorded from bio-pesticide Spinosad treated plot followed by farmers practice (7.95 thrips/plant) and Beauveria bassiana (8.46 thrips/plant) at 4th day after 3rd spray. Maximum marginal benefit-cost ratio was also obtained from Spinosad treated plot (33.09) followed by farmers practice (30.62) and Beauveria bassiana (15.96). This study showed that bio-pesticide Spinosad (Success 2.5 SC) @ 1.2 ml/litre of water three times at an interval of 10 days from the first appearance of thrips infestation may be recommended for the management of thrips of onion.