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Subject:
From:
Juanse Barros <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Tue, 8 Jan 2013 22:08:14 -0300
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*
*

On Tue, Jan 8, 2013 at 6:51 AM, Ghislain De Roeck <[log in to unmask]>
 wrote:

> Against the current, I know ...
> http://www.boerenlandvogels.nl/sites/default/files/JEIT-D-12-00001_0.pdf


Well not that much I guess ...

From Eric Mussen's newsletter 'from the U.C. Apiaries University of
California' Nov/Dec 2012

*Nosema/Fipronil Synergy*

Most beekeepers are familiar with results of studies conducted at the USDA
Beltsville Bee Lab that demonstrated a synergy between imidacloprid and Nosema
ceranae infections. The infections became worse when the bees had been
exposed to the neonicotinoid. A group of researchers in France conducted a
similar experiment and obtained similar results with fipronil and
thiacloprid and Nosema ceranae. The French researchers expanded their
studies on the insecticide fipronil, a phenylpyrazole with the chemical
name (5-amino-1-(2,6- dichloro-á-á-á-trifluoro-p-tolyl)-4-
trifluoromethylsulfinylpyrazole-3- carbonitrile). In this case, they
decided to see if they would induce synergism when the treatments were
administered in four different regimes. In one approach, newly emerged bees
were inoculated with Nosema spores and exposed during the first week to a
sublethal dose of fipronil, right after emerging. In the second case, the
bees were exposed to the fipronil for a week at the beginning, but the
microbe was inoculated a week later. In the third situation, bees were
inoculated with Nosema ceranae right after emerging and the week-long
application of fipronil was applied a week later. Finally, the bees were
treated with both stressors at the same time, after being caged for one
week.

It turned out that over the 23 days of the trials, being exposed to
sublethal levels of fipronil alone, and being inoculated with Nosema spores
alone, did not change mortality very much from that of the controls - between
75 and 80 percent survival. However, when the toxicant and microbe were
combined, the survivorship dropped to between 23 and 39 percent. The only
difference was in timing of the mortality. If either the application of
toxicant or inoculation with the microbe was delayed a week, then the
mortality was delayed but showed a much steeper loss with time.

The authors of the paper suspected that the synergism could go one of two
ways. The toxicant could make the bees more susceptible to infections or
the exposure to sublethal doses might induce stress resistance to
infections. In this case, as in the case of mosquitoes and either
entomopathic fungus Beauveria bassiana or Metarhizium anisopliae and
permethrin, the combination was particularly hard on the insect. With
mosquitoes, that can be good. With bees, that isn't so good.

If you wish to examine this study, it should be available on the Internet.
The title is: "Parasite-insecticide Interactions: A Case Study for Nosema
ceranae and Fipronil Synergy on Honeybee." Authors are Julie Aufauvre, et
al. URL is: doi: 10.1038/ srep00326. The Journal is Scientific Reports 2:
326.

>
>

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