Informatics Publishing Limited

S. R. Wadyalkar ¹, D. L. Wasule ¹, S. J. Bhoyte ¹, R. M. Wadaskar ¹

Affiliations
1 Department of Plant Pathology, College of Agriculture Nagpur 440001, Maharashtra, IN

Abstract

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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A. M. PARIHAR ¹, D. B. UNDIRWADE ¹, R. M. WADASKAR ¹, S. S. MADANKAR ¹

Affiliations
1 Department of Agricultural Entomology, Dr. Panjabrao Deshmukh Krushi Vidyapeeth, Akola - 444104, Maharashtra, IN

Abstract

Effect of various temperatures on the efficacy of five biorationals, viz. Beauveria bassiana (1.15% WP), Metarhizium anisopliae (1.15% WP), Bacillus thuringiensis (0.5% WP), Azadirachtin (300 ppm) and Spinosad (45 SC) in terms of median lethal concentration (LC₅₀) value was evaluated against diamondback moth, Plutella xylostella larvae. The toxicity data for biorationals against P. xylostella on the basis of larval mortality revealed that M. anisopliae (1.15% WP), B. thuringiensis (0.5% WP), Azadirachtin (300 ppm) and Spinosad (45 SC) registered higher effectiveness (lower LC₅₀ value) at 25(sup>o</sup> C whereas, increase in temperature led to declined efficacy of biorationals; whereas, use of entomopathogenic fungi, B. bassiana (1.15% WP) was most effective at 30^o C and revealed lower effectiveness (higher LC₅₀ value) at 25^o and 35^o C temperatures. Data on the influence of temperature on toxicity of biorationals to P. xylostella on the basis of adult emergence revealed lowest LC₅₀ value for B. thuringiensis (0.5% WP) at 25^o C and the efficacy decreased with increase in the temperature, whereas, M. anisopliae (1.15% WP), B. bassiana (1.15% WP), Azadirachtin (300 ppm) and Spinosad (45 SC) were most effective at 30^o C and the higher LC₅₀ value were evident at temperature above 30^o C, indicating the reduced efficacy of biorationals with increase in temperature beyond 30^o C or preference for lower temperature regimes under laboratory conditions.

Keywords

Biorationals, Diamondback moth, LC₅₀, temperature regimes.

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