Neonicotinoid Pesticides and Bees - The Food and Environment ...

It is also vital to understand the disease status of individuals used in pesticide assessments since
both the honeybee (Apis mellifera) and the bumble-bee (Bombus terrestris) perform poorly in
proboscis extension reflex (PER) memory tests when their immune systems were challenged by
lipopolysaccharide.
Honeybees are the target of a large number of viruses with a total of 18 identified to date. Often
virus vectoring by Varroa, which is a significant stressor in honeybee colonies by feeding on the
haemolymph causes a variety of physical and physiological effects on the colony, and results in
infections from viruses which are otherwise present as covert infections resulting in severe disease
and mortality within the colony. In addition viruses can be transmitted within the colony by
trophallaxis, contact, faeces and salivary gland secretions. However to date there are no reports of
interactions between neonicotinoids and viruses
Exposure (update EFSA review) including available data from incident monitoring schemes
Bees are exposed to pesticides via a number of routes and the relative importance of each
depends on the life stage of the insect and the mode of application of the pesticide. Adults may be
exposed directly to pesticides through direct overspray or flying through spray drift, by consumption
of pollen and nectar (which may contain directly over-sprayed or systemic residues), by contact
with treated surfaces (such as resting on recently treated leaves or flowers), by contact with dusts
generated during drilling of treated seeds, or by exposure to guttation fluid potentially as a source
of water or as dried residues on the surface of leaves. The exposure of larvae is primarily via
processed pollen and nectar in brood food. Data available in the literature includes residues in
pollen, wax and nectar within colonies, pollen and nectar residues from plants, in pollen loads on
bees returning to the hives and in adult workers. Such data also includes the residues of
veterinary medicines detected and the distribution of chemicals around the hive.
The routes of exposure of bees to pesticides has been assessed and recently reviewed in an
EFSA Scientific Opinion particularly in relation to quantifying uptake and extended to include other
non-Apis species where data were available. The exposure of bumble bees to pesticides has also
been reviewed and showed there are key times in the year when exposure of queens may be
particularly important in determining the fate of a colony.
A review of residues in bees after pesticide applications in the EFSA review (2012) provides
evidence of the exposure of bees to applications aggregated through all routes of exposure, i.e.
through direct overspray, foraging on treated crops and consumption of treated food and water as
samples were collected over time after exposure. This showed peak residues in the first sample
after application with declines for spray applications over the following week. No data from
systemic seed or soil application field studies were available but residues of imidacloprid and its
Neonicotinoid pesticides and bees Page 7 of 133
Report to Syngenta Ltd