Effectiveness of green muscardine fungus Metarhizium anisopliae and some insecticides on lesser coconut weevil Diocalandra frumenti Fabricius (Coleoptera: Curculionidae)

Abstract

This report aims to evaluate the effectiveness of treatment for lesser coconut weevil (Diocalandra frumenti) with green muscardine fungus (Metarhizium anisopliae) and some insecticides at laboratory and farmers’coconut orchard. The results showed that the isolates of Metarhizium anisopliae at the concentration of 108 spores.mL-1 killed adults under laboratory condition (T = 28-310C; RH = 60-70%). In the laboratory, the corrected effectiveness caused by Metarhizium anisopliae isolates of Ma5, Ma2 and Ma1 had preventive effects at 100%, 95.0% and 95.8% at 15 days after being treated. Both Emamectin benzoate and Fipronil can effectively control the beetles at 100% at 3 days after being treated. Among 4 tested concentrations, the effectiveness of M. anisopliae at 109  spores.mL-1 gave higher effectiveness up to 96.7% at 15 days after being treated. In farmers’coconut orchard, the results also showed  coconut fruits which were damaged by weevils clearly reduced from 35 days after being treated. At 65 days, all of treatments applied with M. anisopliae gave effective control just at 4.00% and 5.60% (ratios of infected fruits). Mainwhile, insecticide applied with treatments had a higher ratio of coconut fruits infected by this weevil (14.7% and 11.4%).