Dr. David Boyle of Maritime MicroBiologicals Inc. reports on his research, on behalf of the New Brunswick Beekeepers Association, into the possibilities of using a beneficial fungus as a biological method of controlling Varroa mites in honey bee colonies:

Biological Control of Varroa Mite of Honey Bee

NBBA and Maritime MicroBiologicals Inc.

As we know too well, Varroa mites are a real problem for beekeepers. Control options are limited, especially since the mites have become resistant to many chemicals that have been directed against them. Therefore, when reports about fungi that controlled Varroa appeared about eight years ago, they were greeted with great interest.

The idea was that these disease-causing fungi, by targeting the mites but not bees (or beekeepers), could be used as biological control agents. Analogous “biocontrols” have been successful against other agricultural pests, so why not use them against Varroa?

Indeed, some subsequent test results were very encouraging (see e.g. paper by Kanga et al. 2006)… but others were not (see James et al. 2006).

In 2006, the NBBA, with financial support from the Canada/NB EIAA program, initiated a research project with Dr. David Boyle of Maritime MicroBiologicals Inc (MMBI), the goal being to assess and further develop this control option.

Initial lab work identified some fungal isolates that killed mites.

Other work served to identify potential reasons for the contrasting results reported in the cited papers.

Foremost among these was high hive temperature, measurements showing that this sometimes went over 35°C. Of the many candidate fungi tested, most became inactive at temperatures over ca 30°C. A few did however continue to grow at 35°C.

Of these, most were of tropical origin, but interestingly, one temperature-tolerant isolate was from New Brunswick. This one is being used in tests being done now.

Another potential problem concerned anti-fungal activity detected in propolis and beeswax. It is hoped that it will be possible to overcome this problem by using appropriate formulation and application methods.

Additional small scale testing of various candidate biocontrol fungi is continuing at MMBI, but to really know if biocontrol of Varroa works, it will be necessary to do the tests in hives. It is hoped that this will happen during a subsequent phase of this project. This will require planning, which should start soon.

For further information, please contact:

Literature cited:

Kanga, H.B, L. Jones, W.A. and C. Gracia. 2006.
Efficacy of strips coated with Metarhizium anisopliae for control of Varroa destructor (Acari:Varroidae) in honey bee colonies in Texas and Florida. Exp. Appl. Acarol 40:249-258

James, R.R., G. Hayes and J. E. Leland. 2006.
Field trials on the microbial control of Varroa with the fungus Metarhizium anisopliae. American Bee Journal. Nov. 2006 issue. Pp. 968-972