The European Food Safety Authority commissioned Helen M Thompson of the Food and Environment Research Agency to produce a report on the "Interaction between pesticides and other factors in effects on bees". She generated a 200 page document which thoroughly covers the topic. She wrote, in part:

This review considered state-of-the-knowledge through search of information from scientific
literature, study reports and other documents. To provide an overview of the interactions
between pesticides and other factors in effects on bees considering:

• The importance of the different exposure routes in relation to the overall exposure of bees
to pesticides.
• Multiple exposure to pesticides (including substances used in bee medication) and
potential additive and cumulative effects.
• Interactions between diseases and susceptibility of bees to pesticides.


Some conclusions:

• There are a wide range of factors which affect the immunocompetence of bees including the
quality of the pollen diet, the presence of other diseases, such as N ceranae, or pests, e.g.
Varroa, and in-hive treatments such as antibiotics. In addition, the confinement of colonies or
individuals may result in stress leading to immunosuppression. It is important that these
factors are taken into account in studies determining the effects of pesticides on both
individual and social immunity.

• The effect of the diet on both the immunocompetence and the xenobiotic metabolising
enzymes within the gut are important and impact on both the effects on the toxicity of other
pesticides and the impacts on disease susceptibility. Pathogens may also impact on some
measures of sublethal effects of pesticides. It is therefore important that the realistic routes of
exposure are used in mixture studies, i.e. oral for contaminated pollen and nectar, and that the
disease status of bees used in pesticide studies is fully understood.

• Currently there is no clear evidence from field based studies that exposure of colonies to
pesticides results in increased susceptibility to disease or that there is a link between colony
loss due to disease and pesticide residues in monitoring studies.

SOURCE:
http://www.efsa.europa.eu/en/supporting/pub/340e.htm

reported by:
Peter Loring Borst
Ithaca NY USA
peterloringborst.com

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