Metarhizium brunneum, a common soil-borne entomopathogenic fungi was evaluated as a potential biological control agent against Varroa destructor, a devastating honey bee ectoparasitic mite. Although previous studies show Metarhizium can infect and kill varroa without harming the honey bee, virulence varies between species, strains, and application methods. Field trials conducted in 2016 tested the ability of a non-conidiating and conidating strain of M. brunneum to infect and kill varroa. Varroa fall onto sticky boards was collected every 48 hours, counted, and plated onto agar. The non-conidiating strain had no effect on varroa population numbers whereas the conidiating strain caused a significant increase in varroa mite mortality compared to control hives.  Peak varroa mortality occurred 5-7 days post treatment, with a decline in mortality starting at day 9; there is a loss of conidia viability at bee hive temperatures (35ºC). 

Presenter: Dr. Jennifer Han, Washington State University

Dr. Jennifer Han is a post-doctoral researcher at Washington State University in Pullman. Jennifer is currently researching the efficacy of Metarhizium brunneum, an entomopathogenic fungi, as a biocontrol agent against varroamites, a devastating honeybee pest.  She is working to improve the theromotolerance and virulence of M. brunneum using directed evolution techniques.  She hopes to develop fungal strains that are hypervirulent towards varroa with minimal negative impacts to honey bees and the surrounding environment.