Re: Entomopathogenic Fungi--Metarhizium anisopliae

There are a couple  of aspect s of Metarhizium anisopliae (& the group
of  entomopathogenic fungi--a group of fungi found to infect insects)
not spelled out in Dee's list of articles.   Different strains have
varying virulence against different families of insects (lepidoptera,
coleoptera, hymenoptera, etc.  Second these fungi are often very
effective in a controlled setting but  can have variable response
because of changing environmental conditions during field evaaluation
which makes it a challenge for commercial development.

Lets start with strains--My guess is that the Metarhizium anisopliae
strain selected for mite control has very little effect on honeybee's.
Same species ( as far as scientist can tell) but different strains have
a profoundly differing effect on differing families of insect.  For
example I'm currently working with a strain of entomopathogenic fungi
that is very effective on a beetle, quite effective on a moth but will
not touch a looper.  Go figure!   Genetic screening may lead to better
information on why this is so. I can select (from the ARSEF culture
collection,
http://www.ppru.cornell.edu/mycology/ARSEF_Culture_Collection.htm)
strains that have been found on specific species of insects that are
ineffective against others in the same family.  This can be exploited,
tested for in the lab, selected for.  So the specific strain selected
for mite control probably has little to no effect against the Honeybee.

Number two--These fungi are very sensitive to environmental conditions,
particularly temperature & relative humidity.  Again laboratory
screening & selection can fine tune final  selection of a safe &
effective strain to be commercially developed to target a specific
insect (or mite in this case).  Safety to concurrent non-target or
beneficial insects is always done prior to roll out. You could not
develop a product that is shown to kill what you are trying to protect.
  Sometimes the actual site of effect is the separator.  For example, If
a fungus only works at cool temperature, say 20 degrees,  probably will
not be a threat to a colony of bees where the internal temperature is
well above that, in effect thermally neutralizing the fungus.
However, one concern might be--but again this will be screened for,
this strain must operate where the mites are which is in a hive at a
fairly warm temperature (by fungal standards) and might be of concern
if M. a. were to slightly infect honeybees.

Overall these fungi are very family specific, very safe ( hey I've
screened hundreds in the lab and never gotten sick) and I hope it
works. We need a diversity of tools to help beekeepers.  As I have seen
it it looks like it would be great if it could be rolled out as a
traditional biocontrol.  By this I mean that the beekeeper could spread
out the pathogen once and the fungus would remain present slowly
killing mites ever after.  However it would probably need to be an
ameliorative release where spores would be spread periodically more
like an insecticide--in this case a mycoinsecticide.

However after a good number of years of working with entomopathogens
leads me to a pragmatic view-

If Metarhizium anisopliae can be developed as a control it will not be
a silver bullet.  It will be another tool in our arsenal.  It may work
well sometimes  at others it may not.  IT may  be difficult to come by
as a commercial product--many companies producing & selling fungal
pathogens as registered control agents have not survived long ($$$)
and finally there may be some dust--fungal spore contamination issues,
pollen collectors may not want to dust, and there may be some weird
microbial balance disruptions because once you add something to a
biotic system things change.
Mike Griggs
http://bees.library.cornell.edu/

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