I would like to clear up a few questions regarding the use of Metarhizium
anisopliae for varroa control. I am a researcher for ARS who has been
working on this project.

First, I would just like to clarify that Green Muscle is a Metarhizium
anisopliae product used for grasshopper (locust) control in Africa. The
product is really a subspecies of the fungus that is very specific to
grasshoppers, and other closely related insects. Thus, it is highly
unlikely that it will work on varroa. However, some of the technology
developed for Green Muscle is useful in developig a varroa product.

Second, the fungus that Bill Ruzicka was working with in the 90's was
Hirsutella thompsonii, and we found that the particular strain he worked
with was not very pathogenic to varroa in lab bioassays. Other strains can
be quite pathogenic. However, that fungus is very difficult to produce and
formulate in a product that will work on bees. I am not saying that it
can't be done, but I had a very difficult time with it and subsequently
gave up the effort.

Last, but not least, I really doubt that we will be able to produce the
silver bullet for varroa control, and especially not in the form of a pill
that you can just drop down the hole in the inner cover. We have been
working on ways to apply spores to the hives, but that has not been one of
them. Beekeepers will have to apply the fungual spores more than once in
the life of a hive, and probably at least once a year. We are still working
on the question of just how frequently applications need to be made.

The beekeeping industry has been verbally very supportive of this project,
and we appreciate that.

--Rosalind James

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