POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
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2. DRIVERS OF CHANGE OF POLLINATORS,
POLLINATION NETWORKS AND POLLINATION
studies. In particular, Goulson (2015), when reanalyzing a
study of the impacts of exposure of bumble bee colonies
to neonicotinoids, showed a negative relationship between
both colony growth and queen production and the levels
of neonicotinoids in the food stores collected by the bees.
Another study at wide field scale observed the effects of
the clothianidin applied on spring sown oilseed rape in
Sweden on managed honey bees and different wild bees
(Rundlöf et al., 2015). They showed that this insecticide had
no impact on managed honey bees but was reducing the
density of wild bees, the nesting of the solitary bee Osmia
bicornis, and the growth and reproduction of the bumble
bee B. terrestris colonies. Though it is unclear whether the
same results would be observed under different conditions
(e.g. different crops, climates, or modes of agriculture) these
results do show for the first time the effects of neonicotinoid
insecticides in field conditions. These new data have a
considerable importance, considering that oilseed rape is
one of the main crops worldwide, and is highly attractive
to bees, such that it competes successfully with other coflowering
vegetation for pollinator visits (Holzschuh et al.,
2011; section 2.2.2.1.7).
Among the reviews published to date, four out of six
(Cresswell, 2011; Van der Sluijs et al., 2013; Simon-
Delso et al., 2014; Pisa et al., 2014) do conclude that
sublethal effects of neonicotinoid insecticides on bees
have negative consequences on their individual and social
performances, suggesting their contribution to the decline
of bees. Such consequences are potentially worsened by
the fact that bees can be attracted by foods contaminated
by neonicotinoid insecticides (Kessler et al., 2015). There
is overall considerable evidence of sublethal effects of
neonicotinoids on bees, but still low agreement on their
in-field exposure levels and subsequent consequences,
resulting in considerable uncertainty about how sublethal
effects recorded on individuals (Figure 2.3.5) might affect
the populations of wild pollinators over the long term. This
knowledge gap makes it particularly difficult to assess how
sublethal pesticide impacts affect the delivery and economic
value of pollination services (Rundlöf et al., 2015; Raine
and Gill, 2015). As highlighted by Johnson (2015) modeling
may provide an approach to improve our understanding
of the potential impact of sublethal effects on honey bee
colonies (Becher et al., 2014) and other pollinators (Bryden
et al., 2013).
Finally, some of the reviews consider that synergistic and
chronic effects have been widely underestimated, and
should be studied much more.
Another issue is whether sublethal effects of pesticide
exposure affect the provision of pollination. A recent study
by Stanley et al. (2015) provided the first experimental
evidence that neonicotinoid exposure can reduce the
pollination delivered by bumblebees (B. terrestris) to apple
crops. Flower visitation rates, amounts of pollen collected
and seed set were all significantly lower for colonies
exposed to 10 ppb thiamethoxam than untreated controls
in flight cages. These findings suggest that sublethal effects
of pesticide exposure can impair the ability of bees to
provide pollination, which could have wider implications for
sustained production of pollinator-dependent crops and the
reproduction of many wild plants. Although currently there
is no evidence of such impacts on pollination under field
conditions (Brittain and Potts, 2011).
2.3.1.5 Evidence of effects of pesticide
mixtures
Pollinators may be exposed to mixtures of pesticides
through a number of routes, including collection of nectar
and pollen from multiple sources, storage of these in
colonies of eusocial bees, tank mixes, and overspray
of crops in flower where systemic residues are present
FIGURE 2.3.6
Analysis of the numbers of reported sublethal endpoints at different levels of organisation reported for the neonicotinoid insecticides
(imidacloprid, clothiandin and thiamethoxam) conducted on Apis, Bombus and other bee species and the relative abundance of data
on specific endpoints (excluding mortality) in honey bee individuals and colonies (as reported in Fryday et al., 2015).
250
Field colony sublethal
Number of endpoints reported
200
150
100
50
0
Apis
Bombus
Other
Semi-field colony
sublethal
Individual mortality
Individual sublethal