Bioprospecting entomopathogens as biopesticides against walnut weevil, Alcidodes porrectirostris Marshall (Coleoptera: Curculionidae)
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Date
2021-09
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Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu
Abstract
The weevil Alcidodes porrectirostris Marshall is a monophagous pest of walnut Juglans regia L. and is responsible for large scale damage of latter especially in Jammu region of J&K. The present day control measures of walnut weevil exclusively rely on application of commercial pesticides. The widespread development of resistance to chemical insecticides and the effects on non-target organisms coupled with regulatory and environmental concerns has stimulated efforts to develop alternative methods for management of A. porrectirostris. The use of entomopathogenic fungi offers an effective alternative to control this weevil because of the characteristic of the former to control the concealed pests. In this direction, investigations on “Bioprospecting entomopathogens as biopesticides against walnut weevil, Alcidodes porrectirostris Marshall (Coleoptera: Curculionidae)” were carried out to isolate and determine the potential of naturally occurring entomopathogens viz., Beauveria bassiana (Bals.) and Metarhizium anisopliae (Metchnikoff) for management of this pest in Jammu region. A total of four entomopathogen fungal isolates, two of B. bassiana Bb-BH1 & Bb-BH2 from Bhaderwah, and two of M. anisopliae Ma-PO1 & Ma-PO2 from Poonch were collected and subjected to morphological characterization under laboratory conditions. The potential of entomopathogen isolates for management of the A. porrectirostris was evaluated on larvae and adults of walnut weevil under laboratory conditions and same was translated for the management of larvae under field conditions. The pathogenicity of isolates was also confirmed through Koch’s postulates.
Prior to the evaluation of pathogenicity of tested fungal isolates, percent potential yield loss caused by A. porrectirostris across different walnut growing locations was estimated. The potential yield loss caused by A. porrectirostris larvae varied from 6.24– 25.63 per cent across Jammu region. The yield loss was found more in Bhaderwah (25.63 per cent) followed by Udhampur (12.34 per cent) with minimal in Reasi (6.24 per cent).The mortality of A. Porrectirostris larvae and adults with four different tested isolates at different concentrations ranged from 10.00-71.66 and 7.50-62.50 per cent, respectively with significant differences between the concentrations in each isolate under laboratory conditions. The highest mortality was observed with the B. Bassiana Bb-BH2 (71.66%) followed by B. bassiana Bb-BH1 (58.33%) in larvae and with the B. bassiana Bb-BH2 (62.50%) followed by B. bassiana Bb-BH1 (47.50%) in adults, respectively. A significant positive correlation between concentration and mortality was also observed. Under the field conditions, high larval mortality was observed with the B. bassiana Bb-BH2 (57.00%) as compared to M. anisopliae Ma-PO1 (35.00%). The LC50 and ST50 values of four entomopathogenic isolates varied from 3.15 × 106 to 1.47× 109 spores/larvae and 9.72× 106 to 3.46× 109 spores/adult, and 8.97 to 13.50 days and 11.98 to 16.67 days, against larvae and adults, respectively. The LC50 and ST50 values of B. bassiana Bb-BH2 isolate were significantly lower as compared to other isolates. It was concluded that B. bassiana Bb-BH2 isolate has a considerable potential for eco-friendly management of A. Porrectirostris and can be used as a promising viable alternative to chemical insecticides in Jammu region. However, further study is demanded to augment the pathogenicity of these isolates for long term use if the dream of organic agriculture is to be relished in real sense.
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Preferred for your work. Guroo, M. A. 2021. Bioprospecting entomopathogens as biopesticides against walnut weevil Alcidodes porrectirostris Marshall (Coleoptera: Curculionidae). Ph.D. thesis, SKUAST-Jammu, India.