The influence of sublethal neonicotinoid doses on individual Apis mellifera scutellata thermotolerance

Abstract

Honey bee (Apis mellifera L.) thermoregulation plays an integral part in their behaviour and physiology and has been shown to be vulnerable to the effects of neonicotinoid insecticides. Baseline thermotolerance of 53.8 °C (defined as LT50; temperature at which 50% mortality is recorded) was determined for this subspecies. We evaluated the influence of sublethal dosages of three widely used neonicotinoid insecticides, clothianidin, imidacloprid and thiamethoxam, on individual Apis mellifera scutellata thermotolerance, each evaluated at a range of increasing ambient temperatures. For all three neonicotinoid treatments, A. m. scutellata thermotolerance was decreased by more than 3 °C as compared to the baseline data. Such a reduction in honey bee thermotolerance, especially under the increasing frequency and intensity of hot weather events, is a cause for concern when considering legislation and use of these neonicotinoids in the South African agricultural and suburban setting.