This is an interesting study from the UK about the pesticide Thiamethoxam. More study is needed but this is very concerning. Pesticide affects for bumblebees may have similar affects on honeybees as well.
“We consistently found that neonicotinoid exposure, at levels mimicking exposure that queens could experience in agricultural landscapes, resulted in reduced ovary development in queens of all four species we tested,” said lead researcher, Dr Gemma Baron of Royal Holloway University of London.
“These impacts are likely to reduce the success of bumblebee queens in the spring, with knock-on effects for bee populations later in the year.”
Read more here from the BBC: Bumblebees: Pesticide ‘reduces queen egg development’