Thermo-tolerance characterization and bioassay of selected entomopathogenic fungal (EPF) isolates on larva of Spodoptera litura Fab.

Abstract

Entomopathogenic fungi viz. Metarizhium anisoplae and Beauveria bassiana are well characterized in respect to pathogenicity to several insects and have been used for biological control of agriculture pests worldwide. Despite their potential, several factors like low resistance to elevated temperature have hindered widespread adoption of fungi as part of biological control regimes. In this study, five isolates of B. bassiana (Bb 01, Bb 02, Bb 03, Bb 04 and Bb 05) and two isolates of M. anisoplae (Ma 01 and Ma 02) were evaluated for thermotolerance capacity and bioefficacy against third instar of Spodoptera litura. Among the isolates studied, Bb 04 recorded the higher temperature tolerance up to 34oC with mean spore germination of 35.00 percent and mean dry mycelial weight of 443.38 mg. Further, in the bioassay studies, Bb 04 caused significantly (@ P<0.01%) higher percent mortality of S. litura larva at 1×108 spores ml-1 on fifth day (80.00 %) with LT50 value of 4.08 days and LC50 value of 2.07×104 conidia ml-1 at five days. Investigation results indicated that BB 04 is a suitable EPF isolate for management of S. litura where higher temperature prevails.