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Metarhizium anisopliae is a potent microbial insecticide against Helicoverpa armigera (Hübner), a potential threat to successful cultivation of many economically important crops, Pathogenicity study conducted with 10⁸ spores/ml concentration of fungal suspention revealed larval mortality of 100.00,90.00,76.67, and 56.67 per cent against I^st, II^nd, III^rd and IV^th instar larvae of H. armigera, respectively. Five media were compared at four temperature levels. Emersons's Yeast Phosphate Soluble Starch (YPSS) medium recorded highest conidial count of 22.00 x 10⁷ spores/ml at 27° C followed. by 25⁰ C, Sabouraud's Dextrose Broth + Yeast (SDB+Y) and Potato Dextrose Broth (PDB) being on par with YPSS at 27⁰ C. Poor cultural growth was recorded in Barners medium at all temperature levels. Amongst the five media used for the mass multiplication studies, Potato Dextrose Broth was found to be hetter in terms of spore production, viability of conidia and its production cost. Bioassay data analyzed by log dose Probit method revealed LC₅₀ values of 6.0x10⁴, 1.2xlO⁶, 4.8x10⁶ and 5.0x10⁷ spores/ml for I^st, II^nd, III^rd and IV^th instar H. armigera larvae, respectively, with very shallow slopes.

Keywords

Helicoverpa armigera, Media, Metarhizium anisopliae, Pathogenicity, Temperature.

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