Natural Incidence of Entomopathogenic Fungus Metarhizium rileyi (Farlow) Kepler S.A. Rehner & Humber (Ascomycetes: Hypocreales) in the Scarce Rainfall Zones of Andhra Pradesh

Metarhizium rileyi (Farlow) Kepler S.A. Rehner & Humber, an entomopathogenic fungus of Lepidoptera, targets many noctuids, which are key pests of agricultural crops. Since indigenous isolates of entomopathogenic fungi are more likely to survive and endure and are better suited to the local climate, employing them to control insect pests is an efficient way to fight pesticide resistance and resurgence. In order to identify and isolate native fungal isolates, a survey was carried out in a number of locations inside Andhra Pradesh’s Scarce Rainfall Zone (SRZ). Insect cadavers were collected for this purpose. The surveys were carried out from October to January 2021-2022 and October to December 2022, during which infected larvae samples were collected from various locations including Kurnool, Anantapur, Prakasam, Kadapa, and Chittoor. The crops surveyed for mummified caterpillars included groundnut, greengram, redgram, tomato, castor, blackgram, rice, onion, chili, soybean, cowpea, and maize. The pests observed during the survey were Spodoptera frugiperda, Spodoptera litura, Helicoverpa armigera, and Aproarema modicella. Most M. rileyi infected cadavers were found in pulse crop infested insects, while no mummified larval cadavers were found in other crops such as brinjal, okra, tomato, cotton, rice, cauliflower, cabbage, and chili. Cadavers from various sites were collected separately in sterilized vials or polythene bags and brought to the laboratory. The average maximum and minimum temperatures reported in the Andhra Pradesh SRZ during the survey period were 29-36°C and 14-28°C, respectively. Rainfall varied from 59.40 to 302.00 mm, while the average relative humidity in the morning and evening was 49-77% and 81-100%, respectively.