Varroa is a relatively new scourge in New Zealand. It was introduced, by accident, around seven years ago. Varroa is a mite, the size of a pinhead, that lives on both the larvae and adult bees.
Large infestations of varroa will weaken your hive and destroy it. Knowing how to treat it is an essential beekeeping skill.
Varroa is a relatively new scourge in New Zealand. It was introduced, by accident, around seven years ago. Varroa is a mite, the size of a pinhead, that lives on both the larvae and adult bees. Large infestations will weaken the hive and destroy it. It is important to treat your hive twice a year, once in spring and again in autumn when you have harvested the last honey for the season. The reason for treating the colony at this time is that there are not many larvae around, which varroa feeds on, so you will get a good 
kill rate. Come spring, newly laid larvae should be pest-free.
There are several commercial preparations you can buy from beekeeping supply stores. As resistance to some preparations is becoming evident, it is recommended to alternate products from different chemical groups. The commercial treatments come in plastic strips. Two of these strips are inserted into the brood camber and left for 6–8 weeks. It is very important to remove them after this time or mite resistance can develop. It costs around $20 dollars a year to treat with these strips.
The top bar hive design helps with integrated pest management of varroa. The mesh floor allows any varroa knocked off adult bees to fall out of the hive. Varroa numbers can also be monitored by placing a piece of sticky paper under the mesh floor and counting varroa numbers.
As resistance to some preparations is becoming evident it is recommended to alternate products from different chemical groups.
As top bar bees build their own comb they naturally build the comb slightly smaller than if building using foundation frames (foundation comb is made bigger so that the bees are forced to fill with more honey). Varroa prefers larger sized comb so there is some evidence that the top bar hive creates a natural resistance to varroa.
Another organic way you can control varroa is to dust your bees with icing sugar. I do this by placing icing sugar in a cheese shaker, or similar, and dusting the bees when I am inspecting the top bar comb. The theory behind this is the bees will groom themselves and knock many varroa mites off in the process.
There are some organic varroa treatments about, some based on thyme. I have heard conflicting reports on their efficiency, but plan to use them alternatively with the mainstream treatments and monitor their success. They are best used when it is still warm so place them in hive in mid autumn.
