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

metabolite 6-chloronicotinic 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 during resting
and cleaning they may transfer residues from their feet to other parts of their bodies.
The exposure of bees to pesticides in pollen depends on both the residues present and the
amounts of pollen collected by the bees. The amount of pollen collected by a colony per day is
highly variable and depends on pollen availability, crop species and the needs of the colony. On
oilseed rape the amount of pollen collected varied with the stage of flowering with most collected in
the latter stage. Bee bread is pollen processed from the pollen loads by bees for storage by
combining with nectar or honey and addition of antimicrobial agents. This results in higher
residues in bee bread than in pollen which may relate to differences in availability for residue
analysis following processing of the pollen by bees.
Flower morphology is an important factor in the pesticide content of nectar: flowers in which the
nectar is deeper, such as clover, were less contaminated than shallower flowers such as cabbage
and nectar yield/flower was less important in determining pesticide content. To date, there are no
reports of pesticide residues in aphid honeydew after spray application but the intake by bees may
be expected to be similar to that of nectar sources.
Residues in honey formed from contaminated nectar and stored within the hive will depend on the
concentration of nectar through evaporation of water to produce honey and degradation of
residues through biological and chemical factors in honey. Both factors are slow and counter each
other to some extent and there are differences between honey contained in open and sealed cells.
The residues of neonicotinoids pesticides detected in stored nectar and honey in field studies and
available monitoring data for samples taken directly from colonies are summarised. Monitoring
data for processed honey has been excluded as honey is combined from a large number of
Neonicotinoid pesticides and bees Page 8 of 133
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