Bob Harrison said:

> The scenario above would have been quite different if we had another 98%
> control chemical (of a completely different chemical makeup) to alternate
> with Apistan would it not George?  Be honest.

> How long in your estimation would Fluvalinate taken to become ineffective if
> alternated with another 98% control chemical

Well, here's what may soon be "another 98% control", but its not a "chemical",
and it clearly works differently from both Coumaphos and Fluvalinate.

Yes, there may soon be a FUNGUS among us!   :)

==========================================================

Varroa Control with Fungal Pathogens may be an Option Soon
From News for South Carolina Beekeepers, Nov. 2002, Vol. 13, No. 3

The honey bee is of great economic importance to agriculture not only for honey
production, but also for crop pollination.  Currently, a parasitic mite, Varroa destructor,
is the most serious threat to beekeeping because it causes weight loss, malformation,
and a shortened life-span in honey bees and serves as a vector of diseases.

Without adequate control measures, bee mortality approaches 100% in hives infested
with the mites and colonies can perish within a few months.  This destructive mite is
now distributed across the United States and most of North America.

Apistan (tau-fluvalinate) and Check-Mite (coumaphos) strips are the most widely used
Varroa controls in the United States and Canada.  Other synthetic Varroa treatments
are labor-intensive, expensive, or leave toxic residues in honey and wax.  Mites
throughout Europe and North America are evolving resistance to miticides, threatening
the bee industry.

As a result, there is an urgent need for alternative control strategies that are cost effective,
environmentally friendly, and safe for human consumption.  As such, microbial control of
Varroa mites with fungi offers promising new avenues for the beekeeping industry.
Unlike bacteria and viruses, these fungi do not have to be ingested to cause infection,
but penetrate the host cuticle directly.  This characteristic makes fungi potentially easier
to apply than other pathogens.

We screened several isolates of the fungi Hirsutella thompsonii and Metarhisium anisopliae,
and found strains of both that were highly pathogenic to Varroa at temperatures similar to
that maintained by honey bees in a colony.  The infection time (the time it took for 90%
cumulative mortality of mites) ranged from 4 to 5 days.  Treating observation hives with
H. thompsonii resulted in a significant mite mortality that was sustained over 42 days.
Peaks in mortality occurred 3-4 days after the spores were applied.  Similarly, in
Weslaco, TX, we tested applications of Metarhizium anisopliae spores using both dusts
and strips coated with the fungus.  Both applications methods resulted in satisfactory
control of mite populations in honey bee colonies, and these fungal treatments were as
effective as Apistan, even 42 days after application.

In addition, the fungal pathogens had no harmful effects in the honey bees and did not affect
the fecundity of the queen.  At the end of the trial (42 days posttreatment), when Apistan strips
were replaced by coumaphos for two weeks, the daily mite-fall counts were similar to those
recorded with Apistan during the trial, suggesting that the mite populations were equally
susceptible to both Apistan and coumaphos.

The mite mortality observed was highly correlated with the number of spores we were able to
recover from the bees that we sampled at different time intervals.  Because workers and
drones drift between hives, the adult bees were found to spread the fungus between hives in
the apiary.  We were also able to recover the fungus from inside the dead mites, confirmation
that the fungus was infecting and killing the mites.  In addition, the pathogen was found to
reproduce on the mites.

We have now established a cooperative research agreement with Sylvan Bioproducts, Inc.
which will assist us in developing methods for producing and formulating the fungi for Varroa
control.  Currently, our research aims at developing more efficient application technology to
reduce the time required per application, and make the treatments economically viable for
beekeepers.  Overall, these fungi show good potential for serving as effective biological control
agents against the Varroa mite.  We hope to be able to offer beekeepers this new avenue of
control in the near future.

Footnote:  Mention of a commercial product does not constitute endorsement by the USDA.

Source:  Lambert H. B. Kanga, USDA, ARS, Beneficial Insects Research Unit, Weslaco, TX and
             Rosalind R. James, USDA, ARS Bee Biology & Systematics Laboratory,
             Utah State University, Logan, UT