Large-scale monitoring of effects of clothianidin-dressed OSR seeds on pollinating insects in Northern Germany: effects on large earth bumble bees (Bombus terrestris)
Large-scale monitoring of effects of clothianidin-dressed OSR seeds on pollinating insects in Northern Germany: effects on large earth bumble bees (Bombus terrestris)
Guido Sterk 0 1
● Britta Peters 0 1
● Zhenglei Gao 0 1
● Ulrich Zumkier 0 1
0 tier3 solutions GmbH , Leverkusen , Germany
1 IPM Impact , Gierkensstraat 21, Kuringen 3511 , Belgium
The aim of this study was to investigate the effects of Elado®-dressed winter oilseed rape (OSR, 10 g clothianidin & 2 g beta-cyfluthrin/kg seed) on the development, reproduction and behaviour of large earth bumble bees (Bombus terrestris) as part of a large-scale monitoring field study in Northern Germany, where OSR 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 10 bumble bee hives were placed at each location. At each site, three locations were directly adjacent to OSR fields and three locations were situated 400 m distant from the nearest OSR field. The development of colonies was monitored from the beginning of OSR flowering in April until June 2014. Pollen from returning foragers was analysed for its composition. An average of 44 % of OSR pollen was found in pollen loads of bumble bees indicating that OSR was a major resource for the colonies. At the end of OSR flowering, hives were transferred to a nature reserve until the end of the study. Colony development in terms of hive weight and the number of workers showed a typical course with no statistically significant differences between the sites. Reproductive output was comparatively high and not negatively affected by the exposure to treated OSR. In summary, Elado®-dressed OSR did not cause any detrimental effects on the development or reproduction of bumble bee colonies.
Bumble bees ● Seed treatment ● Plant protection products ● Neonicotinoids
-
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). However,
several studies suggest that there is a decline in populations
of pollinating insects (Kearns et al. 1998; Biesmeijer et al.
2006; Potts et al. 2010). While domesticated honey bees are
traditionally thought of as the economically most important
pollinator in crop monocultures, bumble bees can also be
important pollinators especially in temperate climates (Free
1970; Corbet et al. 1991). While commercially bred
colonies are available for the use in agriculture (Velthuis and
Doorn 2006), their use is often restricted to greenhouses so
that field crops rely on naturally occurring bumble bee
colonies.
However, declines in populations of bumble bees have
been reported worldwide (e.g., Kosior et al. 2007; Williams
and Osborne 2009; Colla et al. 2012; Kerr et al. 2015).
Multiple stressors may affect bumble bees, e.g., parasites,
lack of floral resources and plant protection products (PPPs)
(Goulson et al. 2015). In agricultural landscapes,
massflowering crops such as OSR serve as a valuable nectar and
pollen source for bumble bees (Westphal et al. 2006 2009),
but, on the other hand, agricultural practices such as the use
of PPPs may pose a risk to pollinating insects.
A class of PPP that has been commonly used in OSR are
neonicotinoids. Formulations containing neonicotinoids
may be used as a seed treatment; their active substances are
systemically taken up by the plants and distributed to all
tissues (Elbert et al. 2008). The use of seed dressing reduces
risks for non-target organisms, as fewer applications at
lower rates are used as compared to foliar spray
applications. However, concerns have been raised regarding 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 suspended in the European
Union in crops attractive to bees (European Commission
2013).
Various laboratory and semi-laboratory experiments
have been performed, where bumble bees were artificially
exposed to ‘field-realistic concentrations’ of neonicotinoids
(e.g., Whitehorn et al. 2012; Feltham et al. 2014). However,
whether concentrations used in these experiments are really
representative for the exposure in the field is still under
debate (Carreck and Ratnieks 2014). Furthermore, existing
laboratory studies for clothianidin (e.g., Franklin et al. 2004;
Scott-Dupree et al. 2009; Scholer and Krischik 2014;
Moffat et al. 2015) are inconsistent in their implications for
bumble bee colonies in the field.
Thus, a key question is how neonicotinoids influence
bees in real world agricultural landscapes (Schmuck and
Lewis 2016). However, only few monitoring studies at the
landscape level have been performed (e.g., Cutler and
ScottDupree 2014; Thompson et al. 2016). To (...truncated)