First report of Metarhizium koreanum, a natural pathogen of Pyrilla perpusilla walker (Hemiptera: Lophopidae)

Pyrilla perpusilla Walker (Hemiptera: Lophopidae) commonly referred to as the sugarcane leaf hopper/ plant hopper, is widespread in Asia and is a severe threat to sugarcane farming, particularly under waterlogged conditions in Andhra Pradesh. In February 2023, natural mycosis was observed on adults and nymphs of the sugarcane leaf hopper in China Ogirala village of Krishna district, Andhra Pradesh. An entomopathogenic fungus was isolated from infected adults and nymphs on Sabouraud’s Dextrose Yeast extract agar in the laboratory following standard protocol. It was then identified by morphological and molecular analysis. Natural infection of P. perpusilla by Metarhizium koreanum under field conditions was noticed in the form of whitish mycelial growth on soft body parts turning into green with sporulation. Stereomicroscopic analysis showed extensive colonization of thorax and abdomen, but sparse growth on the snout, legs, and wings. The fungus was cultured on SDAY medium with the formation of septate hyaline mycelium, branched conidiophores, and ellipsoid conidia. In laboratory bioassays, the M. koreanum PCO1 isolate resulted in the mortality of 81.67% of the adult insects on day 9 after inoculation, LT50 = 6.39 days, and 84.66% of the nymphs at day 6 after inoculation, LT50 = 3.80 days. Molecular identification using ITS and Tef-1α gene sequencing identified the isolate as M. koreanum. Phylogenetic analysis placed the isolate close to M. koreanum strains and well separated from all other species of Metarhizium. This study is the first to report that M. koreanum naturally infects both adults and nymphs of the sugarcane leafhopper P. perpusilla. Preliminary laboratory tests validated that the M. koreanum PCO1 isolate is pathogenic on both life stages of P. perpusilla. These findings provide a foundation for further research into the use of M. koreanum as a biological control agent to manage sugarcane leaf hopper populations.