Effects of Neonicotinoids and Temperature on Crop Pollination

In NEOPOLL we investigate sub-lethal effects of Current Use Pesticides (CUPs) (i.e. the neonicotinoid clothianidin) on important pollinators, namely bumblebees. There is a limited number of studies quantifying the effects of neonicotinoids, in field realistic settings. Studies have shown that both climatic/weather conditions and pesticides negatively affect bumblebees, but the additive effect of these drivers have previously never been studied. We have conducted a laboratory experiment where we monitor individual learning, search behaviour and flower handling under different pesticide exposure levels. These experiments were conducted under two different temperature regimes, 12°C and 28°C, to see whether the negative effects of the pesticide changes with temperature. Our hypothesis was that the negative effect of the pesticide is stronger at lower temperatures, when the bumblebees experience temperature stress. Data from these experiments have not been analysed yet. In relation to this experiment Malin Røyset Aarønes has analysed clothianidin accumulation in the exposed bumblebees and showed that there is accumulation both in the head and bodies of bumblebee workers. She found no effect on brood production and mortality, but the proven accumulation suggest that sub-lethal effects are possible, and that prolonged exposure might have adverse effects. In collaboration with NIVA we have developed laboratory procedures for analysing clothianidin exposure from nectar and pesticide accumulation in bumblebee honey, larvae and workers. These results are presented in master thesis of Aarønes that has now been published in the scientific journal Environmental Toxicology and Chemistry. We have also conducted a semi-field experiment focusing on foraging behaviour. Bumblebees were chronically exposed to two different pesticide doses and later allowed to forage outdoors in natural vegetation. By use of a custom-made video recording system, we have measured individual foraging bouts lengths. In this experiment we also found no effect on brood production and mortality, showing that the exposure levels represented sub-lethal doses. We did find that foraging bout length increased with exposure level but that the effect with the temperature the bumblebees experienced. Control bumblebees (not exposed) were not sensitive to temperature, while bumblebees exposed to low concentrations spent longer time foraging under low temperatures. For the bumblebees subject to high concentrations the effect was even stronger. These results were part of the master thesis of Pawel Kolano and is also published in a special issue in the Journal of Pollination Ecology. We have also conducted several experiments in Reading in collaboration with our partners at The University of Reading. Here bumblebee colonies were exposed to different doses of clothianidin and flupyradifurone under contrasting temperature regimes. Colony development has been analysed and published in the master thesis of Nora Kildebo. We found that the effect of flupyradifurone on colony development (number of workers at the end of the experiment) was lower for flupyradifurone than for clothianidin, but that the effect of flupyradifurone was temperature dependent. Colonies exposed to low doses of flupyradifurone had lower growth at high temperatures, but higher growth at low temperatures, when compared to control colonies (unexposed). For colonies exposed to high levels of flupyradifurone the pattern was reversed; higher growth at higher temperatures and lower growth at lower temperatures. Colonies exposed to high levels of clothianidin had lower growth than control colonies, irrespective of the temperature conditions.

I forbindelse med våre møter hvor Mattilsynet har vært invitert har vi presentert resultater som viser tydelig at de negative effektene av sprøytemidler avhenger av temperaturforhold, da særlig at effektene kan være større under lave temperaturer. Vi håper at disse resultatene blir tatt inn i risikovurderingene av plantevernmidler, slik at de faktiske effektene, under Norske forhold, blir lagt til grunn.

In this project we will investigate how the neonicotinoid clothianidin affect bumblebee behaviour, colony development and ultimately pollination service. First, we will use indoor flight cages to monitor individual behaviour (learning and foraging efficacy) under different exposure to clothianidin. The colonies will be fed sugar solution with increasing concentrations of clothianidin. We will repeat our experiments under different temperature regimes to better understand how the focal pesticide affects bumblebee behaviour under different climatic conditions. In the same colonies we will monitor colony development, i.e. production and mortality of larvae and workers) Second, we will construct a setup where the bumblebees are kept indoors but allowed to forage out in the open. Also here the exposure to clothianidin will be given through sugar solution. We will monitor foraging efficacy by weighing individual bumblebees as they leave the colony and as they return. We will also measure the weight of the entire colony, accounting for the number of workers and larvae present. Third, to get a better understanding of how clothianidin might affect pollination service and ultimately crop yield, we will conduct a semi-field experiment by use of large pollination exclusion cages. Oilseed rape will be grown from treated and untreated seeds and bumblebees will be allowed to forage on them. We will monitor visitation frequencies to assess effects on pollination and count pods and seeds per pod as well as plant yield to assess effects on crop production. Finally we will address the environmental risk assessment (ERA), which is composed of both an exposure and an effects assessment, targeting the link from observed exposure and accumulation from the plants to the bumblebees, and to the observed mortality and more importantly sub-lethal behavioural effects, including pollination.