Description:
Agricultural intensification has increased the number of stressors that pollinators are exposed to. Besides increasing landscape fragmentation, that limit the supply of flower resources, intensive agricultural practices relying on the use of pesticides to control agricultural pests, also affect non-target organisms like honey bees. Most pesticides from the neonicotinoid group have been banned from the European Union, leaving acetamiprid as the only active substance that can still be sprayed outdoors. In the meantime, new substances like sulfoxaflor, that have a similar mode of action acting on the insect’s nicotinic acetylcholine receptors, have been approved for agricultural use. This active ingredient is allowed in the US, but its use in Europe is limited due to toxic effects already reported on bees. In this study homing ability tests with acetamiprid and sulfoxaflor were performed, in which honey bees were fed with three sub-lethal doses from each substance. After exposure, each honey bee was equipped with an RFID chip and released 1km away from the colony to evaluate their capacity to return to the colony - homing ability. Honey bees fed with 32 ng of acetamiprid exhibited a non-significant increase in their homing ability while the highest doses (48 and 61 ng/bee) did not affect their homing ability. Honey bees fed with 26 ng of sulfoxaflor showed a poor performance on their homing ability with only 28% of them reaching the colony instead of 75% registered in the control group. The highest sulfoxaflor toxicity might be related with the honey bees detoxifying mechanisms, which are more effective on cyano-based insecticides (i.e., acetamiprid). With this study we encourage the implementation of homing ability tests in the current risk assessment scheme for honeybees, providing a clear example of how sub-lethal doses could negatively affect honey bees