"Bad weather in spring prevented honey bees in many areas from collecting nectar from early flowering crops such as oil seed rape, and the rain continued in many places throughout June and July preventing honey bees from foraging on later crops, " he said.

BBC: Honey harvest 'devastated' by wet summer

To investigate, scientists looked at two common pesticides: neonicotinoids, which are used to control pests on oil seed rape and other crops, and a group of organophosphate chemicals called coumaphos, which are used to kill the Varroa mite, a parasite that attacks the honey bee.

BBC: Neonicotinoid pesticides 'damage brains of bees'

It is suing him for patent infringement, accusing him of illegally obtaining and planting its oil-seed rape (canola).

ECONOMIST: Canada