Risk assessment for side-effects of neonicotinoids against bumblebees with and without impairing foraging behavior

Abstract

Bombus terrestris bumblebees are important pollinators of wild flowers, and in modern agriculture they are used to guarantee pollination of vegetables and fruits. In the field it is likely that worker bees are exposed to pesticides during foraging. To date, several tests exist to assess lethal and sublethal side-effects of pesticides on bee survival, growth/development and reproduction. Within the context of ecotoxicology and insect physiology, we report the development of a new bioassay to assess the impact of sublethal concentrations on the bumblebee foraging behavior under laboratory conditions. In brief, the experimental setup of this behavior test consists of two artificial nests connected with a tube of about 20 cm and use of queenless micro-colonies of 5 workers. In one nest the worker bees constructed brood, and in the other food (sugar and pollen) was provided. Before exposure, the worker bees were allowed a training to forage for untreated food; afterwards this was replaced by treated food. Using this setup we investigated the effects of sublethal concentrations of the neonicotinoid insecticide imidacloprid, known to negatively affect the foraging behavior of bees. For comparison within the family of neonicotinoid insecticides, we also tested different concentrations of two other neonicotinoids: thiamethoxam and thiacloprid, in the laboratory with the new bioassay. Finally to evaluate the new bioassay, we also tested sublethal concentrations of imidacloprid in the greenhouse with use of queenright colonies of B. terrestris, and here worker bees needed to forage/fly for food that was placed at a distance of 3 m from their hives. In general, the experiments showed that concentrations that may be considered safe for bumblebees can have a negative influence on their foraging behavior. Therefore it is recommended that behavior tests should be included in risk assessment tests for highly toxic pesticides because impairment of the foraging behavior can result in a decreased pollination, lower reproduction and finally in colony mortality due to a lack of food.

Israeli acute paralysis virus associated paralysis symptoms, viral tissue distribution and Dicer-2 induction in bumblebee workers (Bombus terrestris)

“…Callow workers were collected from virus-free colonies of B. terrestris (Biobest, Westerlo Belgium), and kept in microcolonies supplied with sugar water under standardized conditions in an incubator (Panasonic) at 30 C and 60 % relative humidity with continuous darkness (Mommaerts et al, 2010). The IAPV inoculum used in this study was produced by propagating virus reference isolates in 50 white-eyed honeybee pupae and preparing a chloroform-clarified extract in 10 mM phosphate buffer (pH 7.0)/0.02 % diethyl dithiocarbamate as described previously (Niu et al, 2014a).…”

“…We scored specific symptoms of paralysis and trembling, and when these appeared, those individuals were isolated. Additionally, we scored for abnormalities in worker behaviour, such as foraging, feeding and the response of the workers to a gentle shaking (challenge) of the micro-colony where normal workers would fly up immediately (Mommaerts et al, 2010).…”

Negative effects of pesticides on wild bee communities can be buffered by landscape context

“…Of 19 surveyed, two orchards applied petroleum oil early in the growing season to control overwintering mites and scales. With one of the highest application rates (5-8 kg ha 21 ) and relatively high BIQ (18.1), the single application of oil at the two study orchards increased overall pesticide use indices by 22 and 54%. We conducted linear models with and without oils and the results showed similar effects.…”

Investigating the impacts of field‐realistic exposure to a neonicotinoid pesticide on bumblebee foraging, homing ability and colony growth

“…However, not all neonicotinoids have the same toxicity to bees (Mommaerts et al . 2010; Moffat et al . 2015, 2016), so although bees exposed to thiamethoxam have been shown to behave differently when visiting flowers on their first foraging bout (Stanley et al .…”