If you are a beekeeper you need to be aware that the oil seed rape will be sprayed with insecticides when it is in full flower. Hopefully you would have made farmers aware that you have beehives in the area and informed them that you would need to shut your bees in, the night before or very early in the morning before they spray.
BeeConnected is a service bringing farmers and beekeepers together, and keeping beekeepers notified when a neighbouring farmer is applying insecticides to their crops. You will need to register at beeconnected.org.uk but do not just rely on this, make farmers aware that you have beehives. Bees will forage up to five miles away from the hive.