# Analysis of Toxic Components in Secondary Metabolites of Entomopathogenic Fungi Clonostachys rosea (Hipocreales: Bionectriaceae) from Cephalcia chuxiongica (Hymenoptera: Pamphiliidae)

## TL;DR

This study identifies toxic compounds in a fungus that kills pine-forest pests, showing potential for biological pest control.

## Contribution

The study identifies specific secondary metabolites from Clonostachys rosea responsible for its insecticidal activity against Cephalcia chuxiongica.

## Key findings

- The crude extract at 7.5 μg/mL showed highest toxicity, with 65% larval mortality in non-diapause stages.
- Contact toxicity was more effective than oral exposure in killing C. chuxiongica larvae.
- Nine toxic compounds were identified, with eight showing notable contact toxicity except 2-piperidone.

## Abstract

Clonostachys rosea, an entomopathogenic fungus that infects Cephalcia chuxiongica, is highly pathogenic and has significant potential for controlling the damage this pest causes to pine forests. To investigate the role of C. rosea secondary metabolites in fungal pathogenicity, we conducted toxicity assays using crude metabolite extracts. These assays evaluated the effects of different concentrations, larval developmental stages, and exposure methods on larval mortality. Gas chromatography–mass spectrometry (GC–MS) was subsequently employed to identify the chemical constituents of the crude extracts, and the toxicity of the identified compounds was assessed. The results showed that the crude extract at a concentration of 7.5 μg/mL exhibited the highest toxicity. Two hours post-treatment, the mortality rate of non-diapause larvae reached 65%, which was significantly higher than that of the diapause group. Moreover, contact toxicity was more lethal to C. chuxiongica larvae than oral exposure. A total of 23 compounds were identified from the crude extract, of which nine exhibited toxicity: 2-piperidone, hydrocinnamic acid, phenethyl alcohol, oleic acid, tryptophol, stearic acid methyl ester, myristic acid, dodecanoic acid, and benzeneacetic acid. Except for 2-piperidone, which showed low toxicity, the other eight compounds demonstrated notable contact toxicity against C. chuxiongica larvae. These findings confirm the insecticidal potential of C. rosea secondary metabolites and provide a valuable reference for the biological control of C. chuxiongica and other chewing insect pests.