Assessing effectiveness of the green muscardine fungus Metarhizium anisopliae against lesser coconut weevil, Diocalandra frumenti Fabricius in Tra Vinh province

Abstract

The current study assesses the effectiveness of green muscardine fungus Metarhizium anisopliae on the lesser coconut weevil Diocalandra frumenti Fabricius in the laboratory, net house, and filed. Four strains of Metarhizium anisopliae at a concentration of 10⁸ conidia/mL killed adult beetles in the laboratory and net house. In the laboratory, the effectiveness of Ma-CK, Ma-CL1, Ma-TC1, Ma-CL3 is from 68,2% to 91,1% on the 19th day after treatment. Under the net house condition, the effectiveness is from 89,6% to 100% on the 15th day after treating. In the field, the infected rate on the coconut stack is significantly lower than the control on the 21st day after treating. On the 65th day, all of the treatments applied with M. anisopliae gave effective control just from 14,0% to 21,3% (ratios of infected bunches) and from 10,5% to 12,4% (ratios of infected fruits). Meanwhile, control treatments had a higher ratio of coconut bunches and fruits infected by this weevil (45,6% and 35,8%).