Evaluation of entomopathogenic fungi against pest complex of chilli (Capsicum annuum L.)

Abstract

An investigation entitled “Evaluation of entomopathogenic fungi against pest complex of chilli (Capsicum annuum L.)” was carried out during 2012-14 at College of Agriculture, Vellayani. The objectives were to evaluate the efficacy of Beauveria bassiana (Balsamo) Vuillemin, Lecanicillium lecanii Zare & Gams and Metarhizium anisopliae (Metschnikoff) Sorokin against pests of chilli, assess the compatibility of the fungi with pesticides and develop products of the fungi. Three fungi viz. Fusarium solani (Mart.) Sacc and Penicillium oxalicum Currie and Thom infecting Aphis gossypii Glover and Isaria javanica (Friederichs & Bally) Brown & Smith infecting Bemisia tabaci Gennadius were isolated and the reports on these insects are new in India. An yeast, Meyerozyma caribbica (Vaughan-Martini, Kurtzman, S.A. Meyer & E.B. O'Neill) Kurtzman & M. Suzuki infecting B. tabaci has been isolated and the report of the yeast is new. The pathogenicity of fungal isolates was evaluated against A. gossypii, B. tabaci, P. latus and S. dorsalis. All the treated insects showed symptoms of infection by all the isolates except Llm. The virulence of the fungi was evaluated @ 108 spores ml-1. At 48 hours after treatment, the highest mortality of 99.97 per cent to A. gossypii was caused by L. lecanii (Ll8). I. javanica caused the maximum mortality of 83.61 per cent to B. tabaci. With respect to P. latus, the highest mortality of 80.65 per cent was recorded in B. bassiana (Bb5a) and it was on par with the mortality in L. lecanii (Ll8) and B. bassiana (Bb21). The effect of all the fungi except L. lecanii (Llm) to S. dorsalis was on par. The LC50, LC90 and LT50 values of the fungal pathogens to A. gossypii, B. tabaci, P. latus and S. dorsalis were worked out. To achieve control of these sucking pests in the shortest period, the field doses fixed for B. bassiana (Bb5a), B. bassiana (Bb21), L. lecanii (Ll8) and M. anisopliae (Ma4) ranged from 1.68 × 108 to 5.10× 109, 1.68× 108 to 5.75× 109, 2.76× 108 to 4.12× 109 and 3.11× 108 to 3.12× 109 spore ml-1 respectively. Talc based products of the fungi were prepared and their shelf life was determined. The cfu observed at 60 days after storage was 1.03× 108 ml-1, 0.44× 108 ml-1, 0.68× 108 ml-1 and 1.18× 108 ml-1 for B. bassiana (Bb5a), M. anisopliae (Ma4), L. lecanii (Ll8) and Bb21 respectively. The compatibility of the fungal pathogens with pesticides was assessed. Dimethoate (0.06%) was the most inhibitory to all the fungal isolates. M. anisopliae (Ma4) was least inhibited by the pesticides. Field experiment was conducted to evaluate the fungal pathogens and newer molecules of insecticides against pests of chilli. The treatments B. bassiana (Bb5a) and L. lecanii (Ll8) @ 20 g l-1 and acetamiprid (0.004%) were found to be on par in reducing the P. latus population. B. bassiana (Bb5a) 20 g l-1 was found on par with acetamiprid (0.004%), spiromesifen (0.02%) and emamectin benzoate (0.002%) in their effectiveness to S. dorsalis at 7 DAT. The fungal isolates did not affect the spider population. The benefit cost ratio was highest for the treatment with B. bassiana (Bb5a) 20 g l-1 (2.62). To conclude, the fungal pathogens viz. B. bassiana (Bb5a and Bb21), L. lecanii (Ll8) and M. anisopliae (Ma4) @ 20 g l-1 are safe, economical and ideal for integration with newer pesticide molecules viz. emamectin benzoate (0.002%), spiromesifen (0.02%) and acetamiprid (0.004%) for management of pest complex of chilli.