Field Dynamics of Entomopathogenic Fungi Attacking Sugarcane Planthopper, Pyrilla Perpusilla (Lophopidae: Hemiptera) in a Managed Agro-Ecosystem Comprising Sugarcane Germplasm

A three-year field study was carried out in a managed agro-ecosystem comprising sugarcane germplasm in the Malabar region of Kerala (Kannur), India to characterize the field dynamics of entomopathogens infecting nymphs and adults of sugarcane planthopper, Pyrilla perpusilla. The peak pyrilla population was noticed during June-July and the minimum during November–December. Entomopathogenic fungi (EPF) belonging to two genera viz., Metarhizium and Hirsutella were found to cause mycosis in nymphs and adults of P. Perpusilla with nymphal mortality by Metarhizium being higher than that caused by Hirsutella across the sampling period. The peak period of adult mortality by Metarhizium was recorded during the June–August monsoon period whereas adult mortality by Hirsutella was noticed during August–December post-monsoon period. The mummified cadavers bearing synnemata killed by Hirsutella, which served as a point of source for new infections had remained on leaves for a longer duration than that of Metarhizium. The spatial distribution analyses indicated that the dispersion of live adults was weakly aggregated to random and the dispersion of mummified adults was regular. In contrast, live and mummified nymphs were highly aggregated. Correlation analysis revealed that there was a significant and positive correlation between the live pyrilla population and monthly weather factors viz., relative humidity (RH), rainfall, and rainy days. The prevalence of monsoon and humid conditions with the daily average RH consistently clocking higher than 70% during the assessment period positively supported the occurrence of pathogenicity from entomopathogenic fungi. The study outcome emphasizes the conservative agricultural practices and strategies for the augmentative use of EPF for the sustainable management of P. perpusilla in sugarcane.