Impact of Temperature on Pesticide Effects in Bumblebees

The impact of pesticides on bumblebees is strongly influenced by temperature, a finding highlighted by researchers at Imperial College London. Certain pesticides, particularly some neonicotinoids, are known to reduce the numbers of bumblebees and other essential pollinators. Explanations for this effect vary globally and do not fit a single model. Recently, British scientists demonstrated that the strength and character of this impact can change markedly with temperature. In their study they observed six behavioral parameters of bumblebees under the influence of two pesticides, the neonicotinoid imidacloprid and the sulfoximine sulfoxaflor, across three temperatures: 21, 27 and 30 degrees Celsius. Imidacloprid exhibited a stronger influence on four behavioral parameters at lower temperatures, specifically reaction rate, propensity to move, walking speed, and the rate of food intake. These findings indicate that pesticides may disrupt nest maintenance tasks more severely in cooler conditions. Yet the effect on flight range, a key indicator of foraging and overall activity, showed the greatest sensitivity to higher temperatures. Flight distance remained consistent between 21 and 27 degrees, but declined sharply at 30 degrees. The maximum flight range of bumblebees and other pollinators is a critical factor in ensuring successful crop yields and protecting wild plant populations. The researchers emphasize that farmers and others in the agro-industrial sector should consider these temperature-dependent effects when applying pesticides to field areas. The study also underscores a potential vulnerability for bumblebees in the face of global warming, signaling that rising temperatures could intensify certain risks to pollinator health and ecosystem services.