Hi all

For years, while the rest of the world seems hell bent on proving that bees are succumbing worldwide to neonics, many of us having been trying to point out that the role of fungicides has been overlooked

Honeybee colony disorder in crop areas: the role of pesticides and viruses
Noa Simon-Delso, et al

As in many other locations in the world, honeybee colony losses and disorders have increased in
Belgium. Some of the symptoms observed rest unspecific and their causes remain unknown. The
present study aims to determine the role of both pesticide exposure and virus load on the
appraisal of unexplained honeybee colony disorders in field conditions.

From July 2011 to May 2012, 330 colonies were monitored. Honeybees, wax, beebread and honey
samples were collected. Morbidity and mortality information provided by beekeepers, colony
clinical visits and availability of analytical matrix were used to form 2 groups: healthy colonies and
colonies with disorders (n=29, n=25, respectively). Disorders included: (1) dead colonies or
colonies in which part of the colony appeared dead, or had disappeared; (2) weak colonies; (3)
queen loss; (4) problems linked to brood and not related to any known disease. Five common
viruses and 99 pesticides (41 fungicides, 39 insecticides and synergist, 14 herbicides, 5 acaricides
and metabolites) were quantified in the samples.

The main symptoms observed in the group with disorders are linked to brood and queens. The
viruses most frequently found are Black Queen Cell Virus, Sac Brood Virus, Deformed Wing Virus.
No significant difference in virus load was observed between the two groups. Three acaricides, 5
insecticides and 13 fungicides were detected in the analysed samples. A significant correlation was
found between the presence of fungicide residues and honeybee colony disorders. A significant
positive link could also be established between the observation of disorder and the abundance of
crop surface around the beehive. According to our results, the role of fungicides as a potential
stressor for honeybee colonies should be further studied, either by their direct and/or indirect
impacts on bees and bee colonies.

Hazards of pesticides to bees - 12th International Symposium of the ICP-PR Bee Protection Group

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