Sub-lethal effects of neonicotinyl insecticide (imidacloprid) colony exposure on honey bee (Apis mellifera L.) queen fecundity

Several factors have contributed to honey bee (Apis mellifera L.) decline in the US for the past five years including systemic neonicotinyl insecticides pervasively used in agriculture and ornamental plants to target various insect pests. Neonicotinoids can induce detrimental sub-lethal effects on individual worker bees such as impaired foraging, learning, and memory through direct consumption of the insecticide from nectar or pollen.  Less studied are the potential effects of neonicotinoids within a colony, particularly on the queen bee and worker larvae, which are fed indirectly through trophallaxis from worker bees. To assess sub-lethal effects of neonicotinyl insecticides on honey bee queen fecundity and brood viability, small colonies in observation hives were fed imidacloprid (0, 20, 50, 100 ppb) in sugar solution.  Two colony sizes (different number of worker bees) were tested to determine influences of colony size on queen and larval exposure rate. Queen egg-laying and locomotive activity were evaluated, and larvae and pupae were quantified after 3 weeks of exposure to assess impacts on brood production. Adult workers that developed during imidacloprid exposure were counted and weighed to assess effects on larval development.  Preliminary data suggests adverse effects of imidacloprid exposure on queen egg-laying ability and locomotive activity and on brood production and worker bee weight. This study will improve our understanding of how neonicotinoids may impact core functions, reproduction, growth and development, of honey bee colonies.