Biological control of Strophosoma spp. (Coleoptera: Curculionidae) in greenery (Abies procera) plantations using Hyphomycetes

Abstract

In Abies procera plantations Strophosoma melanogrammum and S. capitatum cause economic damage due to the adult stage feeding on the needles. No chemical treatments of these weevils are allowed in Denmark, so the potential of biological control was evaluated. We studied pathogenicity of thirteen isolates of entomopathogenic fungi and the field effect of soil application of Metarhizium anisopliae against Strophosoma spp. All of the tested isolates were capable of causing infections under laboratory conditions and average survival time at 20°C ranged between 13 and 23 days for S. melanogrammum and between 23 and 28 days for S. capitatum when dipped in a fungal suspension adjusted to 1×10⁷ conidia mL⁻¹. Under field conditions up to 90% of the living collected individuals died due to M. anisopliae infection in the treated plots, whereas less than 1% died of M. anisopliae infection in control plots. In accordance, the population of Strophosoma spp. was reduced in plots where the fungus was applied compared to control plots.

Keywords:

• Bioassay
• field studies
• Metarhizium anisopliae
• microbial control

Acknowledgments

The authors are greatly indebted to Stephen P. Wraight, two anonymous reviewers and Editor Mark S. Goettel, whose comments greatly improved the manuscript. Francoise Vermeylen, Office of Statistical Consulting, Cornell University gave statistical advice. Ann E. Hajek and Victoria Miranda, Cornell University corrected the English phraseology. Jan Martin, Chris Lomer (†), Holger Philipsen, Rasmus Eliasen, Charlotte Fisher, Karen Marie Kjeldsen and Jon Martin assisted in field work and development of ideas. Stefan Bech Skov and Hans Christian Jessen (The Danish Forest and Nature Agency) gave permission to use field plots. Peter Lüth, Stephan Brückner and Sebastian Kiewnick, from Prophyta GmbH in Germany, provided fungal material for the field experiment. All the above mentioned persons are thanked. Financial support was given by the Danish Environmental Protection Agency (Grant no. 7041-0317 and 7041-0081) and EU (BIPESCO, EU FAIR6 CT–98–4105).