# Endophytic Beauveria bassiana Blastospores Enhance Susceptibility of Ostrinia furnacalis to Chlorantraniliprole via Modulating Immune-Related Pathways

## TL;DR

A fungus called Beauveria bassiana makes corn borer larvae more vulnerable to insecticides by weakening their defenses.

## Contribution

Blastospores of B. bassiana enhance insecticide effectiveness by modulating immune pathways in Ostrinia furnacalis.

## Key findings

- Larvae feeding on fungus-colonized maize showed reduced food intake, slower growth, and higher mortality.
- Blastospores suppressed protective enzymes and detoxification genes while activating stress-response genes.
- Transcriptomic analysis linked increased insecticide susceptibility to downregulated detox genes and upregulated HSP70.

## Abstract

The Asian corn borer (Ostrinia furnacalis) is a major pest that causes significant damage to maize crops worldwide. Current control methods rely heavily on chemical insecticides, which can lead to environmental concerns and pest resistance. In this study, we explored an eco-friendly alternative using the beneficial fungus Beauveria bassiana. We found that when corn borer larvae fed on maize plants colonized by the fungal blastospores, they ate less, grew more slowly, and had higher mortality. Importantly, these larvae became more sensitive to the common insecticide chlorantraniliprole, meaning lower doses could be effective. Our findings indicate that the fungus weakens the larval defense system by suppressing protective enzyme activities and detoxification gene expression, while simultaneously activating stress-responsive genes. This research demonstrates that combining endophytic fungi with reduced amounts of chemical insecticides could provide a more sustainable and environmentally friendly approach for managing corn borer pests in agriculture.

Endophytic colonization by entomopathogenic fungi represents a promising sustainable pest management strategy. This study investigated the physiological and molecular effects of maize endophytically colonized by Beauveria bassiana (strain BbOFDH1-5) conidia and blastospores on the Asian corn borer, Ostrinia furnacalis. We evaluated larval development, protective enzyme activities, and subsequent susceptibility to the insecticide chlorantraniliprole, utilizing gut transcriptomic analysis to elucidate the underlying mechanism. Results demonstrated that larvae fed on maize colonized by either spore type, particularly blastospores, exhibited significantly reduced food consumption, body weight, and survival rates. Additionally, the activities of protective enzymes (SOD, POD, CAT) were markedly suppressed. Feeding on blastospore-colonized maize significantly increased larval susceptibility to chlorantraniliprole. Transcriptomic analysis revealed that this enhanced sensitivity is linked to the downregulation of detoxification-related genes, ABCC4, and the upregulation of stress-response genes such as HSP70. These findings confirm that B. bassiana blastospores can synergistically enhance the efficacy of chemical insecticides by impairing larval physiology and suppressing gut-associated resistance mechanisms, providing a novel basis for integrated pest management.