# Growth Inhibition, Mortality Induction, Adverse Impacts of Development, and Underlying Molecular Mechanisms of Thymol Against Spodoptera frugiperda

## TL;DR

Thymol, a natural compound, inhibits the growth and causes mortality in fall armyworm larvae, offering a potential eco-friendly pest control method.

## Contribution

This study reveals the molecular mechanisms by which thymol affects Spodoptera frugiperda larvae using RNA-Seq analysis.

## Key findings

- Thymol at 2.0 and 4.0 mg/g significantly inhibits the growth and development of S. frugiperda larvae.
- RNA-Seq identified 1754 and 1022 differentially expressed genes affected by thymol treatments.
- Thymol impacts genes related to chitin metabolism, cuticle synthesis, and digestion processes in larvae.

## Abstract

The fall armyworm, Spodoptera frugiperda, is an economically important pest that has caused extensive damage to many crops all around the world over the past decade. Due to the advantages of being bioactive, biodegradable, and ecologically safe, thymol, one of the principal ingredients identified in essential oils, has exhibited its potential in pest control. However, the effects and toxicological mechanisms of thymol on S. frugiperda are still unclear. In this study, we evaluated the bioactivity of thymol on the larvae of S. frugiperda. RNA-Seq was performed to explain the preliminary toxicological mechanisms of thymol on larvae by the identification and functional enrichment analyses of differentially expressed genes (DEGs). Overall, our findings indicate that thymol also exhibits the potential for the control of S. frugiperda.

The global migratory pest, Spodoptera frugiperda, has garnered widespread attention due to the serious damage it inflicts on agricultural productivity, particularly in maize. Thymol is a phytochemical that exhibits functional diversification in plant defense, encompassing antibacterial activities and insect pest management. However, the impact of thymol on S. frugiperda is still undetermined. This study examined the growth inhibition and mortality induction in S. frugiperda larvae after thymol exposure. The detrimental effects of 2.0 and 4.0 mg/g thymol treatments on the growth and development of S. frugiperda were also examined. RNA-Seq was used to investigate the probable toxicological mechanism of thymol on S. frugiperda, resulting in the identification of 1754 and 1022 DEGs impacted by 2.0 and 4.0 mg/g thymol treatments, respectively. The DEGs associated with chitin metabolism and cuticle synthesis, hormone biosynthesis, and protein and fat digestion were subjected to additional analysis. Our findings demonstrate the efficacy of thymol in controlling S. frugiperda and lay the groundwork for understanding the molecular toxicological mechanisms of thymol on larvae.