Sublethal effects of crop protection on honey bee pollination: foraging behaviour and flower visits

Crop protection strategies essential for pest and disease control can pose risk to pollinators. Fruits cannot be grown commercially without the use of crop protection agents, either from organic or chemical origin. The use of products with toxic effects is banned during flowering, and precise pre-flowering intervals have to be respected in Good Agricultural Practice. Bee pollination is essential for fruit crops to guarantee maximal fruit quality (shape and size) and quantity (yield weight). Fruit growers in Belgium depend mostly on non-commercial beekeepers to provide sufficient colonies for adequate pollination. Under optimal circumstances, beekeepers and fruit growers have mutual benefits from this cooperation as both honey and fruit yield increase. In those European countries with a monitoring scheme, acute bee poisoning incidents have decreased considerably and hardly cause problems at present. In recent years, some concerns arose around sublethal effects (i.e., behavioural changes) of chemical crop protection on bees, especially with regard to increased winter mortality. Even though short-term effects can indeed be induced in individually exposed bees, studies that exposed complete colonies did not reveal any long-term consequences at colony level. However, from the fruit growers' viewpoint, potential short-term effects on foraging behaviour are relevant as they can bear on pollination efficacy.