Isolation and virulence of entomopathogenic fungi against larvae of hazelnut weevil Curculio nucum (Coleoptera, Curculionidae) and the effects of combining Metarhizium anisopliae with entomopathogenic nematodes in the laboratory

Abstract

An approach to ensure effective pest biocontrol would be to select native isolates of biological control agents (BCAs). A survey to isolate entomopathogenic fungi (EPF) from a hazelnut growing area has been carried out. EPF were recovered from 133 of the 295 soil samples. The main species isolated were Metarhizium anisopliae sensu lato (36%) and Beauveria bassiana sensu lato (42.8%). With regard to controlling abiotic factors, altitude had an effect on the distribution of B. bassiana, but not on M. anisopliae. Cropping system did not have an effect on the occurrence of these EPF, while pH appeared as a predictive variable for both. In addition, we tested the virulence of six of these isolates: three M. anisopliae and three of B. bassiana against larvae of Curculio nucum L. The highest larval mortality (reaching 80%) was due to M. anisopliae (strain 34) when applied in simultaneous combination with four entomopathogenic nematode species: Steinernema carpocapsae (strain B14), Steinernema feltiae (strain D114), Steinernema. sp. (strain D122) and Heterorhabditis bacteriophora (strain DG46). The effect of nematodes was greater and no antagonistic or synergistic effects were observed.

Keywords:

• Metarhizium
• Beauveria
• Steinernema
• Heterorhabditis
• combination
• synergism

Acknowledgements

This research was supported by a Spanish Ministerio de Educación y Ciencia Project (AGL2006-037228/AGR). Many thanks to Gonçal Barrios, Jordi Mateu, Anna Aymamí from the Servei de Sanitat Vegetal (Generalitat de Catalunya) and Frederic Mallol (ADV Associació pel Desenvolupament Rural de les Muntanyes de Prades) for all their effort and help and to Helena Sanchez and Romina Torre for the technical assistance. We thank Rob Nunny for language revision of the manuscript.