Evaluation of indigenous fungal isolates and Metarhizium anisopliae var. acriidum against adult lesser wax moth, Achroia grisella (l) (Pyralidae: Lepidoptera)

Abstract

The lesser wax moth (LWM) is a widely distributed and devastating insect pest to the honey production sector in Ethiopia. The present study aimed at investigating the potential of native fungal isolates against the lesser wax moth and assessing non target effect of one isolate of Beauveria (IITA 18) and five isolates of Metarhizium (IMI 330189, DLCO-AA83, DLCO-AA 109, DLCO-AA5, DLCO-AA14) via inoculating Ethiopian honeybee race, Apis mellifera bandasii. The effects of these six fungal isolates were evaluated in the laboratory for their pathogenicity to adult lesser wax moths. Spore dilutions were prepared in 0.5% Tween 80. Adults were treated by spraying 2 ml of conidial suspensions ranging from 2x10⁴ to 2x10⁷ conidia/ml. Adult lesser wax moths were found to be susceptible to all isolates and concentrations used. Comparison of post-treatment mortality of adult, lesser wax moth (LWM) at the lowest concentration (2x10⁴ conidia/ml) revealed that infection of > 90% could be achieved by day 8 post inoculation. Investigation into effects of mycosis on percentage emergence of adults from fungal treated last instar larvae of the lwm showed no significant difference (P>0.05) between the treated and untreated controls. Laboratory based experiments on the host specificity of the six fugal isolates had no effect in which only 1 individual honeybee (0.5%) was infected with isolate IITA 18 (Beauveria spp.) while isolate DLCO-AA83 (Metarhizium spp.), caused infection in 2 individual honeybees.