Selection of (Hypocreales: Cordycipitaceae) strains to control (Curculionidae: Scolytinae) females.

BACKGROUND

Eichhoff (Coleoptera: Curculionidae) is an ambrosia beetle reported to affect avocado trees ( Mill.). The use of the entomopathogenic fungus (EPF) (Bals.-Criv.) Vuill. for ambrosia beetle control represents an alternative to insecticides.

METHODS

This study was designed in two stages to select strains with potential to control females. In the first stage, 19 Mexican strains from EPF collection, isolated from Coleoptera (CHE-CNRCB, http://www.gob.mx/senasica/documentos/coleccion-de-hongos-entomopatogenos), were tested. Analyses included radial growth rate, conidial yield, spore germination, and germ tube length. Results were analysed by Principal Component Analysis (PCA) to identify clusters within favourable growth phenotypes. For the second stage, 10 selected strains were re-analysed for virulence-related metabolic characteristic, including cell wall-bound cuticle-degrading enzymes-Pr1-like proteases and β-N-acetyl glucosaminidases (NAGase) chitinases, conidial hydrophobicity and monopolar germination parameters. A second PCA analysis was run for those virulence parameters analysed, and upon results strains CHE-CNRCB 44, 171, 431 and 485 were selected and tested against females. Females were treated with a 1 × 10 conidia mL suspension (recommended rate), using a Potter Tower.

RESULTS

All strains showed insecticidal activity, inducing up to 58% mortality; about 30% dead beetles developed aerial mycelia (CHE-CNRCB 485) and the fastest mortality rate was = 1.95 (CHE-CNRCB 44).

CONCLUSION

Since all selected strains showed virulence against females, results indicated the possibility of selecting strains based on multiple metabolic attributes, as a preliminary test to perform bioassays against order-related target insects.