BIOEFFICACY OF <em>METARHIZIUM</em> <em>ANISOPLIAE</em> ISOLATES AGAINST TEAK SKELETONISER <em>PALIGA</em> <em>MACHOERALIS</em> (LEPIDOPTERA: PYRALIDAE)

Abstract

SAPNA-BAI N, REMADEVI OK, SASIDHARAN TO, BALACHANDER M & DHARMARAJAN P. 2013. Bioefficacy of Metarhizium anisopliae isolates against teak skeletoniser Paliga machoeralis (Lepidoptera: Pyralidae). Paliga machoeralis is the most malicious pest of teak responsible for epidemic defoliation of trees in plantations and natural forests. Metarhizium spp. have been a long standing model for biological control reported to have great potential for the management of over 200 insect species. The present study was conducted to evaluate the virulence of M. anisopliae isolates against P. machoeralis in the laboratory. Bioassay of 25 isolates of M. anisopliae was carried out using inoculum concentrations ranging from 103−108 conidia ml^-1. The dose-mortality and time-dose-mortality responses for these isolates were determined. Median lethal dose concentration (LC₅₀) values of isolates ranged from 0.11 × 105 to 3417.65 × 105 conidia ml^-1. Among the 25 isolates, MIS2, MIS7, MIS1 and MIS3 were found to be more effective with lower LC₅₀ values. MIS2 was
the most effective isolate with lowest LC₅₀ (0.11 × 105 conidia ml^-1) followed by MIS7 (0.15 × 105 conidia ml^-1). Lowest median lethal time (LT₅₀) of 3.4 days was also recorded for MIS2 followed by MIS7 (3.7 days), MIS1 (4.3 days) and MIS3 (4.9 days) at spore load of 107 conidia ml^-1. With respect to LC₅₀ and LT₅₀, MIS2 proved to be superior over other isolates. The results indicate prospects of isolates MIS2 and MIS7 in developing biopesticide formulation for management of teak skeletoniser.