At this time of year, a colony of bees will naturally start to produce males in readiness for the swarming season so it is a good moment to use a simple, chemical-free method of Varroa control.
In the photo below which was taken yesterday, you can see the domed male cells on the upper part of the frame and the flatter worker cells below.
One way of reducing the number of Varroa mites on honey bees is to encourage the colony to produce lots of male larvae and then to remove the resulting pupae before they emerge. Given a choice, Varroa females will lay their eggs on male bee larvae because these take longer to pupate inside their cells so giving more time for the Varroa to reproduce.
Yesterday, I opened one of my hives to put in an entire frame of male cells which had already been drawn out last year. This morning, on the tray underneath the hive I saw piles of debris where the bees had spent the night cleaning up the frame ready for laying by the queen.
Debris on the collector tray from the newly inserted frame of male cells
At lunchtime today, it was warm enough so I opened up the hive again to see what was happening on the frame and sure enough, there was the queen laying eggs in the newly cleaned cells. These cells should be capped by the worker bees in nine days’ time and I will then be able to remove the whole frame and with it, a good proportion of the Varroa mites in the hive.
The queen inspecting the cells to see where she should lay. Eggs (like small grains of rice) can be seen in the bottom of the cells in the clear area where there are no bees.
The queen laying an egg. She has her abdomen pushed right down to the bottom of the cell where she will stick the egg. Notice how all her attendants have formed a circle round her as they watch her progress.
If I do this three times in quick succession, I should have removed sufficient Varroa mites to avoid having to treat the hive in any way until after the honey harvest in August.