Investigating Metarhizium anisopliae for control of the biting midge Culicoides brevitarsis

Summary

The biting midge Culicoides brevitarsis is the principal vector of bluetongue and Akabane viruses in cattle in Australia. The aim of this project was to investigate Metarhizium anisopliae, a fungal pathogen that infects and kills insects, as a control option for C. brevitarsis. Four different isolates of Metarhizium were used in the testing. Adult C. brevitarsis were killed, dying 3-8 days after walking on a substrate treated with M. anisopliae indicating that it has potential as a surface treatment or topical application control strategy. Incorporating Metarhizium into freshly excreted cattle dung, where the midge develops for up to 14 days, reduced the emergence of adult midge to very low levels indicating that Metarhizium has the potential to control C. brevitarsis at the larval stage if fed to cattle. Dung beetles play an important role in pasture management so the potential of Metarhizium to affect dung beetle populations was also investigated. Metarhizium was found to infect dung beetles with infection and mortality rate varying between isolates. However, one isolate capable of controlling C. brevitarsis was found to have a minimal affect on dung beetles.