Characterization and biocontrol potential of a naturally occurring isolate of Metarhizium pingshaense infecting Conogethes punctiferalis

Abstract

An entomopathogenic fungus was isolated from an infected larva of Conogethes punctiferalis (Guen´ee) (Crambidae: Lepidoptera), a highly polyphagous pest recorded from more than 120 plants and widely distributed in Asia and Oceanic countries. The fungus was identified as Metarhizium pingshaense Q.T. Chen & H.L. Guo (Ascomycota: Hypocreales) based on morphological characteristics and molecular studies. Scanning electron microscopic studies were conducted to study the infection of C. punctiferalis by M. pingshaense. Bioassay studies with purified conidial suspension proved that the isolate was highly virulent to C. punctiferalis, causing more than 86 % mortality to fifth instar larvae at 1 × 108 spores/mL, under laboratory conditions. The median lethal concentration (LC50) of the fungus against late instar larvae was 9.1 × 105 conidia/mL and the median survival time (MST) of late instar larvae tested at the doses of 1 × 108 and 1 × 107 conidia/mL were 4.7 and 6.4 days, respectively. The optimal temperature for fungal growth and sporulation was found to be 25 ± 1 ◦C. This is the first report of M. pingshaense naturally infecting C. punctiferalis. Isolation of a highly virulent strain of this fungus holds promise towards development of a potential mycoinsecticide against this pest.