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

equirements. There data can be used to identify possible RUDs but limited confidence can
be held in these.
There was insufficient data available to assess the exposure of solitary bee species.
2.6 Sublethal and chronic effects of neonicotinoids
A large number of studies have been undertaken ion the sublethal and chronic effects of
neonicotinoid pesticides on bees. These are summarised in Tables 37-47 and show the wide
range of dosing approaches and endpoints reported in both Apis and non-Apis (primarily
Bombus) species. Data for fipronil are included in the tables for completeness but as there
are no data available for residues in nectar the data are not discussed further.
2.6.1 Honeybees
The reported effects of neonicotinoids on honeybees under laboratory conditions is shown in
Table 11 to Table 14. By far the majority of the reported literature relates to imidacloprid..
Table 15 to Table 18 summarise the semi-field and field studies reported with neonicotinoid
insecticides and fipronil again the majority of the studies relate to imidacloprid given the
concerns about the limited dataset for the RUD the rates used have been compared in
Figure 3 and Figure 4. These show that a large number of dosing studies have been
conducted at dose rates and concentrations in excess of the reported maximum
concentrations for imidacloprid and thiamethoxam in nectar following use as seed
treatments. Where effects were observed at or below rates close to this value (studies 4,
11,19 and 31 for imidacloprid) three were related to biomarkers such as acinus diameter in
the hypopharangela gland, the proboscis extension reflex to sucrose, and one (Belien et al
2010 a short summary paper where detailed data were not available) was associated with an
adverse colony level effect at 1 µg/Kg. There were far fewer studies with thiamethoxam and
none reported effects at or below the maximum field nectar residue reported (5.2 µg/Kg)
following seed treatment.
2.6.2 Bumblebees
Table 19 to Table 21 summarise studies undertaken with non-Apis species. The vast
majority have been undertaken with bumble bees and Figure 5 shows that in many
imidacloprid was used at concentrations in excess of the maximum rate reported in nectar
although the study by Whitehorn et al (2012) using colonies dosed in the laboratory and
Laycock et al (2012) using worker only microcolonies does report effects following dosing at
field realistic rates. Figure 6 highlights that only a small number of studies have been
undertaken in bumble bees with clothianidin and thiamethoxam and they do not show effects
at field realistic rates.
2.6.3 Conclusion
A large number of studies have been undertaken on the sublethal and chronic effects of
neonicotinoid pesticides on bees using a number of different exposure scenarios and
endpoints and by far the majority of the reported literature relates to imidacloprid that a large
number of dosing studies have been conducted at dose rates and concentrations in excess
of the reported maximum concentrations for imidacloprid and thiamethoxam in nectar
following use as seed treatments. Where effects were observed at or below rates of
imidaclorpid close to the maximum reported in nectar only one appears to be a nonbiomarker
effect at the colony level. There were far fewer studies with thiamethoxam and
Neonicotinoid pesticides and bees Page 45 of 133
Report to Syngenta Ltd