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Subject: Entomology × Author: Kalita, Biraj × End date: 2019 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Efficacy of some biopesticides and synthetic insecticides against banana leaf and fruit scarring beetle, Nodostoma subcostatum Jacoby (Coleoptera: Chrysomelidae)
    (2018) Kalita, Biraj; Gogoi, Inee
    Field and laboratory experiments were conducted in the experimental farm, Department of Horticulture, Assam Agricultural University, Jorhat and Department of Entomology, Assam Agricultural University, Jorhat during 2017-18to evaluate in vitro and in vivo efficacy of biopesticides and synthetic insecticides against banana leaf and fruit scarring beetle A preliminary laboratory bioassay was carried out to determine the LC50 and relative toxicity of the treatmentsviz., azadirachtin 0.03 EC, Beauveria bassiana WP, Metarhizium anisopliae WP, imidacloprid 17.8 SL, profenofos 50 EC along with check chlorpyriphos 20 EC and control. From the present work on bioassay, the order of toxicity with respect to LC50 values was profenofos 50 EC>imidacloprid 17.8 SL>azadirachtin 0.03EC>Metarhizium anisopliae WP>Beauveria bassiana WPfor the exposure period of 1,3 and 5 days, respectively.For field bio efficacy, the treatments were tested at three critical stages of growth of the banana plant and among the treatments tested, chlorpyriphos @ 0.05% proved to be the best treatment at all the three stages of growth in perusal of its ability in reducing the beetle population at 3, 7 and 15 days after treatment, followed by profenofos @ 1.5 L/ha and imidacloprid @ 20 g a.i./ha. Among the biopesticides, azadirachtin @ 2.5 L/ha arrayed up itself as the best over the other two. Plants that were bud injected with imiacloprid registered highest pulp to peel ratio, fruit weight, bunch weight, yield and B:C ratio. Seasonal incidence of leaf and fruit scarring beetleon Dwarf Cavendish was recorded at fortnightly intervals from May, 2017 to April, 2018. Highest population and scars were recorded during second fortnight of September, 2017 and lowest during first fortnight of January, 2018. The average population and scars produced by the insect showed positive and significant correlation with various meteorological factors except morning relative humidity. Multiple regression analysis of beetle population and scars produced by Nodostoma subcostatum with different meteorological parameters showed 69.2 % variation in population and 72.6 % variation in scars due to the combined effect of various meteorological parameters. On considering all the above facts and figures and hitherto due to nonexistence of other anticipatory technology, the bud injection method with imidacloprid and azadirachtin proved to be safer and competent preventive technique for reducing the percentage of blemished fruits (<15%) caused due to banana leaf and fruit scarring beetle in comparison to spraying method of application. This technology required very less quantity of pesticides and was able to keep the original superficial fruit peel appearance and significance, which in turn will able to fetch better price on quality fruits in market and provide financial profit to banana growers and traders.