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

2.5 Exposure of bees to pesticides
See EFSA 2012 http://www.efsa.europa.eu/en/supporting/pub/340e.htm.
Conclusions
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 metabolite 6-chloronitoctinic acid and fipronil and its metabolites were
detected at low levels in monitoring studies
Studies on residues deposited as dust containing neonicotinoids are summarised obviously
this does not take into account recent EU requirements to limit dust emissions through the
use of professionally treated seeds and deflectors. Drift during agricultural treatment
determines the deposition of pesticides within a small distance from the field edge. What is
less obvious is how to calculate the drift onto flowering weeds in the field margin as dust drift
is unlikely to behave in the same way as spray drift due to the wide variations in particle size.
Unfortunately the deposition data generated to date for grasses and flowering weeds in
flower margins have limitations in terms of the reporting of sowing rates and seed treatment
rates.
Contact of bees with treated surfaces may occur through resting on treated leaves or during
foraging on treated flowers. The major issue is that bees do not come into contact with the
treated plant over the entire surface of their body but primarily through their feet; however
Neonicotinoid pesticides and bees Page 42 of 133
Report to Syngenta Ltd