I’ve just treated all my colonies with oxalic acid this afternoon. That should hopefully see off most of the varroa in the colonies and help them get off to a good start this year. All the colonies were alive and strong, which is a relief after the recent prolonged cold spell.
Now is the ideal time to treat, as there should be little brood in the hives after the cold spell. Leaving it a couple more weeks would probably not have been as effective as by then the queen could have started laying a few eggs. Oxalic acid treatment is effective against varroa on the adult bees but has no effect on mites in sealed brood cells. Oxalic acid can also do some harm to brood. Hence it is imortant to time the treatment to coincide with the colonies having no or minimum brood.
The easiest and safest way to apply the treatment is by dribbling a solution of oxalic acid in sugar syrup onto the bee cluster. You can buy ready made solutions which is the easiest and safest way. I lift the crown board, count the number of seams* of bees and then fill a syringe with 5ml of solution x number of seams. i.e. with 6 seams of bees I fill the syringe with 30ml. This is then slowly dribbled onto the bees spreading it as evenly as possible across the bees.
Having opened up all the colonies I now know that three of my colonies will benefit from being given some fondant. Although they are OK right now, they don’t have a lot of spare stores and I would rather not take any chances. If they don’t need it they won’t eat it, but if they do, it will keep them alive.
* by ‘seam’ I mean the number of gaps between the frames that contain bees. At this time of year colonies are clustered and don’t occupy all the seams as they usually do in the summer.