Isolation and identification of <i>Metarhizium anisopliae</i> from <i>Chilo venosatus</i> (Lepidoptera: Pyralidae) cadaver

Abstract

Sugarcane stem borer, Chilo venosatus Walker (Lepidoptera: Pyralidae) is a significant sugarcane pest in South China. Conidia or mycelia collected from the surface of sugarcane stem borer cadavers were cultured. The colony morphology, mycelia and conidial yield were observed with three-agar culture media: potato dextrose agar medium (PDA), potato dextrose with 1% (w/v) peptone agar medium (PPDA), and oatmeal agar medium (OMA). 16 different isolates were identified as Metarhizium anisopliae (Metschnikoff) based on macromorphological, micromorphological, and molecular characteristics, and PPDA was the better culture medium for vegetative growth and conidial yield (10⁹ conidia/ml) than PDA (10⁸ conidia/ml) and OMA (10⁸ conidia/ml). To confirm whether these isolates were pathogenic to  C. venosatus, their virulence to the sugarcane stem borer was tested in the laboratory. Both HS (10 isolates) and LY (6 isolates) strains were pathogenic to C. venosatus. Several highly virulent strains were screened in vitro (the mortalities of the eight isolates HS1, HS6, HS7, LY2, LY3, LY6, HS3 and HS9 were from 96 to 100%), and tests for controlling the sugarcane stem borer were preliminarily performed in vivo. The results show that significant (p=0.01) reductions in adult population were caused by the strains. So, M. anisopliae isolated from the cadavers of C. venosatus Walker is a potential biocontrol agent against this pest in South China.

Keywords: Metarhizium anisopliae, isolation, identification, Chilo venosatus, culture medium, biological control