# Isolation, Identification, Biological Characterization, and Pathogenicity of Entomopathogenic Fungus from the Larvae of the Evergestis extimalis (Scopoli) (Lepidoptera: Pyralidae)

## TL;DR

A pathogenic fungus, Mucor hiemalis, was isolated from Evergestis extimalis larvae and shown to effectively control the pest, especially in younger larvae.

## Contribution

Identification and characterization of Mucor hiemalis QH01 as a novel biocontrol agent for Evergestis extimalis.

## Key findings

- Mucor hiemalis QH01 was identified as a pathogenic fungus infecting Evergestis extimalis larvae.
- The fungus showed higher pathogenicity to younger larvae, with significant survival reduction in second instar larvae.
- Optimal growth conditions for M. hiemalis QH01 were determined as SDAY medium, fructose, peptone, 25°C, pH 6.0–7.0, and a 0:24 light:dark cycle.

## Abstract

Evergestis extimalis is a significant pest of rapeseed crops. During our study on the biology of E. extimalis, we discovered a strain of pathogenic fungus that infected its larvae. Through morphological and molecular biological analyses, the strain was identified as Mucor hiemalis and named M. hiemalis QH01. Afterwards, the optimal growth conditions for strain QH01 were determined by evaluating mycelial growth rate and sporulation yield as indicators. We evaluated the pathogenicity of M. hiemalis against the larvae of the E. extimalis under laboratory conditions. The results indicated that the strain was highly pathogenic to the younger larvae, followed by the older larvae. Subsequently, the pathogenicity of the strain against the second instar larvae of the E. extimalis was further evaluated under greenhouse conditions. The results showed that the survival rate of the second instar larvae decreased significantly. Our findings will contribute to the development of M. hiemalis for the biological control of E. extimalis.

At Qinghai agriculture districts, Evergestis extimalis poses a significant threat to spring rapeseed cultivation through its larvae burring into the rapeseed kernels and feeding seeds. To protect the ecological environment of the Qinghai–Tibet Plateau, it is essential to research and develop biological control technologies for pest management. In this study, we isolated and purified a new entomopathogenic fungus from the carcasses of E. extimalis larvae, which was identified as Mucor hiemalis based on morphological characteristics combined with ITS rDNA and 18S rDNA sequence analyses. Subsequently, the optimal growth conditions for the strain were determined as follows: SDAY medium, fructose as the carbon source, peptone as the nitrogen source, 25 °C, pH 6.0–7.0, and a 0:24 (light:dark) photoperiod.However, UV can significantly reduce fungal spore production. The bioassay result shows its pathogenicity was a concentration-dependent effect on E. extimalis, and younger larvae were more susceptible. With 1 × 108 spores/mL inoculated, survival of second instar larvae decreased by the greenhouse pot experiment. In conclusion, M. hiemalis exhibits a significant biocontrol potential against E. extimalis.