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

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 colonies and therefore residues may be diluted. For pesticides (not
acaracides) the residues detected in the monitoring studies are lower than those reported in
field studies.
Water is collected by honeybees to dilute thickened honey, to produce brood food from
stored pollen, to maintain humidity within the hive and to maintain temperature within the
brood area. Water is not stored in combs by temperate bee colonies. The amount of water
required depends on the outside air temperature and humidity, the strength of the colony
and the amount of brood present. The production of water by evaporation of nectar to form
honey may address at least some of this need. Water consumption by honeybee colonies
has been assessed using confined of colonies provided with a source of water within the
hive. To date there have been no published studies that demonstrate significant exposure of
bees to guttating crops as a source of water in the field. Guttation fluid is unlikely to be
identified by honeybees as a source of sugar due to the low levels present. Bees are less
subject to dessication than most terrestrial insects due to their nectar diet and high metabolic
water production
Beeswax is produced by worker bees within the colony to house stores of nectar and pollen
and for brood production. Production begins when the worker is slightly less than one week
old, peaking at around two weeks and then reducing. It takes between 24 and 48 hours for
any particular honeybee worker to produce a moderate-sized wax scale. If unchanged by a
beekeeper wax within the colony may accumulate lipophilic residues over time both from
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