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Large-scale monitoring of effects of clothianidin-dressed oilseed rape seeds on pollinating insects in Northern Germany: effects on red mason bees (Osmia bicornis)
Large-scale monitoring of effects of clothianidin-dressed oilseed rape seeds on pollinating insects in Northern Germany: effects on red mason bees (Osmia bicornis)
Britta Peters 0
● Zhenglei Gao 0
● Ulrich Zumkier 0
0 tier3 solutions GmbH , Leverkusen , Germany
The aim of this study was to investigate the effects of Elado® (10 g clothianidin & 2 g beta-cyfluthrin/ kg seed)-dressed oilseed rape on the development and reproduction of mason bees (Osmia bicornis) as part of a large-scale monitoring field study in Northern Germany, where oilseed rape is usually cultivated at 25-33 % of the arable land. Both reference and test sites comprised 65 km2 in which no other crops attractive to pollinating insects were present. Six study locations were selected per site and three nesting shelters were placed at each location. Of these locations, three locations were directly adjacent to oilseed rape fields, while the other three locations were situated 100 m distant from the nearest oilseed rape field. At each location, 1500 cocoons of O. bicornis were placed into the central nesting shelter. During the exposure phase, nest building activities and foraging behaviour were assessed repeatedly. Cocoons were harvested in autumn to assess parasitization and reproduction including larval development. The following spring, the emergence of the next generation of adults from cocoons was monitored. High reproductive output and low parasitization rates indicated that Elado®-dressed oilseed rape did not cause any detrimental effects on the development or reproduction of mason bees.
Solitary bees ● Osmia ● Seed treatment ● Plant protection products ● Neonicotinoids
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Pollination is one of the most essential ecosystem services
provided by nature not only to wild plant species, but also
for a number of arable crops (Klein et al. 2007). While
domesticated honey bees (Apis mellifera) are traditionally
thought of as the economically most important pollinator in
crop monocultures, recent research indicates that wild bee
pollinator species can be equally important (Garibaldi et al.
2013). Solitary bees are able to provide pollination services
in certain crops with similar or sometimes superior level of
efficiency (Bosch et al. 2006). In this regard, it has been
shown that they can replace honey bees (Winfree et al.
2007) or act synergistically with them (Garibaldi et al.
2013; Brittain et al. 2013). However, several studies imply
that populations of pollinating insects decline (Kearns et al.
1998; Biesmeijer et al. 2006; Potts et al. 2010). As one of
the factors responsible for the observed decline the
intensification of agriculture was identified, which might also
endanger pollination services (Goulson et al. 2015).
In Central Europe, a crop of high economic value is
oilseed rape (OSR). Mass-flowering OSR fields were found
to have a strong positive influence on the abundance of
generalist solitary bees (Holzschuh et al. 2013) and bees
of the genus Osmia have been shown to be efficient
pollinators of OSR (Jauker et al. 2012a). Furthermore, several
studies indicated that high amounts of OSR at the landscape
scale have positive effects on solitary bees nesting in
seminatural habitats (Jauker et al. 2012b; Diekötter et al. 2014).
However, foraging in agriculturally managed fields also
enhances the risk of pollinating insects to be exposed to
PPPs, which might potentially harmful. Unmanaged (wild)
pollinators are considered to be more vulnerable than honey
bees due to different foraging behaviour and the fact that
nesting sites cannot be moved or covered during PPP
applications (Scott-Dupree et al. 2009), which is mostly
relevant for spray applications.
One class of PPPs commonly used in OSR are
neonicotinoids. Formulations containing neonicotinoids are often
used as seed treatment; their active substances are
systemically taken up by the plants and distributed to all tissues
(Elbert et al. 2008). The use as a seed dressing reduces the
risk for non-target organisms, because fewer applications
and lower rates are used than in foliar spray applications.
However, concerns have been raised about the exposure of
flower visiting insects due to the potential presence of the
substances in nectar and pollen (Blacquière et al. 2012).
Due to these concerns the use of the three neonicotinoids
imidacloprid, clothianidin and thiamethoxam was
temporarily banned in the European Union in crops attractive to
bees (European Commission 2013) to allow for more
studies on potential side effects on pollinators.
Despite their ecological value and their potential as
pollinators in certain crops, solitary bees were not part of
the testing regime routinely used for the registration of
PPPs. It should be noted that the toxicity of products may
vary between Osmia and A. mellifera (Ladurner et al. 2005;
Biddinger et al. 2013). Also, differences in life history
strategies and foraging behaviour may alter the risk under
field conditions. Only recently have solitary (...truncated)