BIO-EFFICACY OF BIOPESTICIDES AGAINST Helicoverpa armigera (Hübner) INFESTING PIGEONPEA
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Date
2004-09
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Abstract
Investigations were carried out on “Bio-efficacy of biopesticides against Helicoverpa armigera (Hübner) infesting pigeonpea” during the years 2002 and 2003 at the College of Agriculture, Gujarat Agricultural University, Junagadh. The salient findings of the research are as follows. Considering the effectiveness and economics of different treatments Bt @ 1.0 kg/ha + endosulfan 0.035 per cent and Bb @ 1.5 Kg/ha + endosulfan 0.035 per cent per cent were found as effective as the recommended synthetic insecticides (endosulfan 0.07 %) for the ecofriendly management of H. armigera in pigeonpea, when they were applied twice first at 50 per cent flowering and second at 50 per cent pod formation. The treatments of Bt @ 2.0 kg/ha and Bb @ 3.0 kg/ha alone were found to be next effective ones. The results of the laboratory bioassays confirmed the results regarding field efficacy of biopesticides alone and in combination with insecticides against H. armigera.
The mortality of Helicoverpa larvae due to B. bassiana @ 2.0 g/lit showed a consistent decrease in all the six instars. Early instars larvae were found the most susceptible as compared to later instars. The cumulative (larva + pupa + adult) moratality in all the sixth instars ranged from 62.56 to 97.50 per cent with an average of 84.12 per cent. The persistence of B. thuringiensis @ 2.0 kg/ha became half within 3 days and caused the mortality in H. armigera larvae up to 7 days. The persistence of B. bassiana @ 3.0 kg/ha became half within 3 days and caused the mortality in H. armigera larvae up to 11 days. At higher dose of Bt i.e. 2.0 kg/ha had an adverse effect on larval feeding and oviposition of H. armigera. The topical spraying of B. bassiana @ 3.0 g/lit caused low pupation of Helicoverpa larvae and highest per cent deformed adults in post-larval development of H. armigera. During post-pupal development of Helicoverpa highest per cent deformed adults was recorded when B. bassiana @ 3.0 g/lit was applied through irrigation method. Thus, both the application methods (spraying and irrigation) of Bb proved to be equally effective in affecting the post-development of Helicoverpa larvae. The addition of sticker viz., Velvet 0.1 per cent was found the most effective to enhance the effectiveness of biopesticides. The neem extract viz., NSKE 5 per cent increased the potentiability of biopesticides when it was mixed.
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Bio-efficacy, biopesticides, Pigeon pea