Studies on mycosis of Metarhizium (Nomuraea) rileyi on Spodoptera frugiperda infesting maize in Andhra Pradesh, India

Abstract

Background Mycosis on the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), infecting maize was observed in research farm of Regional Agricultural Research Station, Anakapalli from October 2019 to February 2020. Main body High relative humidity (94.87%), low temperature (24.11 °C), and high rainfall (376.1 mm) received during the month of September 2019 predisposed the larval instars for fungal infection and subsequent high relative humidity and low temperatures sustained the infection till February 2020. An entomopathogenic fungus (EPF) was isolated from the infected larval instars as per standard protocol on Sabouraud’s maltose yeast extract agar and characterized based on morphological and molecular analysis. The fungus was identified as Metarhizium (Nomuraea) rileyi based on ITS sequence homology and the strain was designated as AKP-Nr-1. The pathogenicity of M. rileyi AKP-Nr-1 on S. frugiperda was visualized, using a light and electron microscopy at the host-pathogen interface. Microscopic studies revealed that all the body parts of larval instars were completely overgrown by white mycelial threads of M. rileyi, except the head capsule, thoracic shield, setae, and crotchets. The cadavers of larval instars of S. frugiperda turned green on sporulation and mummified with progress in infection. In vitro pathogenicity tests revealed the potential of AKP-Nr-1 strain of M. rileyi in management of S. frugiperda. Short conclusion The results indicated the potential of M. rileyi AKP-Nr-1 as biocontrol agent for management of the fall armyworm. This AKP-Nr-1 strain of M. rileyi needs further evaluation under field conditions to evaluate its efficacy against S. frugiperda and its effects on other hosts.

Identification of entomopathogenic fungus Metarhizium rileyi infested in fall armyworm in the cornfield of Korea, and evaluation of its virulence

“…Then, it gradually changed to olive blue, and sporulation began from the 12th day. This is similar to the results of Visalakshi et al (2020), who showed sporulation at 10 days and onwards.…”

“…Entomopathogenic fungi (EPF) are effective biocontrol agents that can provide an alternative for the integrated pest management of FAW. EPF pathogenicity is significantly affected by various environmental conditions, such as humidity, rainfall, and temperature, in a species‐specific manner (Maurya et al, 2013; Visalakshi et al, 2020).…”

“…Among the EPFs, Metarhizium rileyi (Farlow), previously known as Nomuraea rileyi , is effective against several lepidopteran pest species, including S. frugiperda (Visalakshi et al, 2020), S. litura , and Helicoverpa armigera (Keller & Zimmermann, 1989). It produces airborne conidia, which can adhere to the body surface of host insects and germinate, develop a germ tube that penetrates the host cuticles, and colonize the insect's hemocoel, resulting in the insect's death (Srisukchayakul et al, 2005).…”

“…Previous studies have identified various isolates of M. rileyi from different geographical regions and demonstrated their pathogenicity against important agricultural pest species (Devi Vimla et al, 2003; Keller & Zimmermann, 1989; Visalakshi et al, 2020). However, there have been no studies on the identification of potential biological control agents for the invasive FAW in Korea.…”

Virulence of Beauveria sp. and Metarhizium sp. fungi towards Fall armyworm (Spodoptera frugiperda)

“…Unlike most synthetic insecticides, biological control agents are often host speci c and hence tend to have less effect on non-target species and the broader environment (Dodd 1959 (Dodd 1959), and entomopathogenic fungus (Beauveria bassiana) to control coffee berry borer (Hypothenemus hampei) in Colombia (Aristizábal et al 2016) and many more (van Lenteren et al 2018). In India and Uganda, various species of parasitic wasps and nematodes, predatory insects, and fungi have been implicated as playing important roles in suppressing S. frugiperda populations (Firake and Behere 2020; Visalakshi et al 2020;Otim et al 2021), highlighting the potential value of biological control, particularly within broader IPM systems.…”