# Isolation and Characterization of Beauveria caledonica (Ascomycota: Hypocreales) Strains for Biological Control of Odoiporus longicollis Oliver (Coleoptera: Curculionidae)

## TL;DR

Researchers isolated and tested a fungus called Beauveria caledonica to control banana pseudostem weevils, a major pest affecting banana crops in China.

## Contribution

This is the first study to identify and evaluate B. caledonica as a potential biological control agent for Odoiporus longicollis in Yunnan, China.

## Key findings

- Four strains of Beauveria caledonica were identified from banana pseudostem weevils in Yunnan, China.
- The Cs-1 strain showed high virulence with 86.67% lethality after 20 days at high spore concentration.
- Greenhouse tests demonstrated that B. caledonica-treated weevils caused significantly less damage to banana plants.

## Abstract

The banana pseudostem weevil (BPW), Odoiporus longicollis (Oliver), is one of the most destructive pests of bananas that is seriously affecting the yield and quality of bananas. We isolated pathogens from banana pseudostem weevils in Xishuangbanna and Dongchuan, Yunnan, China, and explored their biological characteristics. The pathogenicity of the strains was verified through laboratory and greenhouse inoculation experiments. The results showed that four strains of fungi were identified and confirmed as Beauveria caledonica (Bc) via ITS-rDNA sequencing. Optimal in vitro culture conditions were found to be a photoperiod of 24 h light, 25 °C temperature, and 18 days on potato dextrose agar (PDA) medium with insect meal. Under these conditions, the Cs-1 strain achieved a colony diameter of 65.17 ± 0.74 mm and spore production of 1.24 × 108 cfu/cm2. The Cs-1 strain had the shortest lethal time (LT50) of 9.36 days at an inoculum of 1.00 × 109 cfu/mL, with a lethality of 86.67% after 20 days. The Cs-3 strain showed 77.78% lethality at 1.00 × 108 cfu/mL after 20 days. Despite variations in virulence, lethality did not correlate with major cuticle-degrading enzymes. The Cs-3 strain demonstrated effective biocontrol in greenhouse tests. Banana plants suffered significant damage without Bc-treated BPW, while the treated plantlets thrived. The mortality rate reached 82.78% after 35 days. This study marks the first identification of these entomopathogenic fungi (EPF) in Yunnan, China, highlighting B. caledonica’s potential for biocontrol application.