Effects of winter and spring rape seed treatment with neonicotinoids on honey bees

Abstract

Potential impacts of neonicotinoids (thiamethoxam and clothianidin) on honey bees (Apis mellifera L.) were explored in 2016–2018. The study aimed to evaluate the effects of thiamethoxam and clothianidin used for seed treatment of winter and spring rape (Brassica napus L.) on honey bees under Lithuanian conditions and to quantify the levels of neonicotinoids in the dust released during the sowing operation. Honey bee colonies were established for further field testing and sample collection. The samples of nectar, pollen and bee bread were analysed for neonicotinoid residues. The potential impact of the seed treatment with thiamethoxam and clothianidin on the normally developed bee colonies was investigated in 2017 and 2018. The obtained findings suggest that when sowing neonicotinoid-treated winter and spring rape seed in a dry soil, the concentrations of neonicotinoids in the dust released during the sowing operation were three times as high as the maximum permitted limit (0.05 mg kg-1) set by the European Committee for bee products. The residue levels of neonicotinoids detected in the honey, pollen and bee bread samples were minimal (±0.01 ng g-1). However, no evidence was found to indicate the negative effects of the nicotinoid-seed treatment on the development of bee colonies, wintering, well-being, and honey production.