Abstract
Malnutrition and pesticide exposure are severe factors contributing to the current losses of honeybee colonies. As these stressors often occur combined, we studied the synergistic effects of different diets and pesticide exposure on food choice and mobility of Apis mellifera. We fed beehives with different food sources and exposed the bees to sublethal doses of thiacloprid. After that three different types of honey and pollen were offered in separate choice assays and behaviour towards food was recorded. Thiacloprid significantly affected the food choice in the honey assay, increasing the bees’ preference of polyfloral honey, while pre-pesticide diet had no influence. The pollen choice remained similar regardless of treatments, as bees always preferred polyfloral pollen. Interestingly, pesticide exposure affected bee mobility differently, depending on the previous diet. These results indicate that the diet is an important factor influencing the susceptibility to pesticides.
Highlights
Honeybees contribute to ecosystem services by pollinating a large variety of wild and cultivated plants on which other biological processes and service-providing organisms depend on (Kremen et al 2007)
Monofloral honey is clearly favoured by control bees that had not been treated with pesticides, whereas pesticide-treated bees change their choice towards polyfloral honey (Fig. 2a)
We found out that pesticide exposure changed bee food preference towards polyfloral honey, while bees always preferred polyfloral pollen
Summary
Honeybees contribute to ecosystem services by pollinating a large variety of wild and cultivated plants on which other biological processes and service-providing organisms depend on (Kremen et al 2007). Losses of managed colonies have been recorded all over the world (Steinhauer et al 2018; Requier et al 2018; van Engelsdorp and Meixner 2010) The reasons for this are manifold and include diseases, constant intensification of agriculture, increase of monocultures, and the closely linked excessive use of agrochemicals, all together leading to habitat loss and a reduced availability of a balanced nutrition (Goulson et al 2015). Neonicotinoids are currently the most used insecticides in the world (Craddock et al 2019) They are systemic pesticides, implying that they end up in all parts of the plants, including pollen, nectar, and guttation fluids. This allows an effective and holistic protection against herbivores, and means that non-target organisms like pollinators are exposed to the neurotoxic compounds. The concentrations present in pollen and nectar may not cause direct mortality, but even sublethal doses can have far-reaching effects on the orientation and memory of honeybees (Yang et al 2008), endangering the individuals’ foraging-ability and affecting the survival of the whole colony (Henry et al 2012)
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