Everything Varroa

by Dennis van Engelsdrop

Part 5

Tools to Control cont.

As a rule of thumb, 5% of beekeepers own 95% of the colonies and what they do to manage their colonies is completely different than the 95% of the beekeepers who own 5% of the colonies, which are the backyard beekeepers. The following results are from an experiment of a grad student in Belgium. She wanted to compare the US situation with the Belgium situation. She wanted to concentrate her effort on this region. We know that treatments and their effectiveness are regionally dependent. As we know, treating in Mississippi in August is ridiculous because everywhere is too hot and all the honey’s gone, so they changed it to June. She used high levels of cuomafos, hop guard wasn’t very efficient, amatraz was very efficient. What combinations worked? As it turns out, you probably need to treat a lot fewer times than in the north. It goes against the convention of the continuous brood we’re in, but it’s consistent.

Over three years, we saw no effect for people who used screened bottom boards and two years we did see an effect. You’re losing 4-18% of your mites but if you have a treatment in there, it removes them from the population. You’re slowing resistance build-up. Every time you open a colony, it increases the number mites that get dropped. We know this because we put water treatments as our control treatment on some colonies and we see increased mite drops. It’s not from the water, it’s from the fact that we put the water on the colony and open it. Moving your colony around with screened bottom boards, you’ll lose mites too. I don’t think you need to shut these down in the winter. Colonies are very good keeping at the cluster size; I would not close my screened bottom boards. In the Northern states, there is a much more dramatic and significant effect than in the Southern states.

Brood Management

Next, I want to talk about brood management and drone brood removal. if I was drilling my comb and I found a frame that had more than a fist-sized frame of drone brood, i would call that comb because drone brood is a great breeding grounds for mites. If you really wanted to produce drones, put a drone comb in there so you know where the mites are. Drone brood removal works because varroa mites prefer drones. If there was a way to pull the drones out regularly, it would be great because then we can remove the drones and the varroa that are feeding on them. If you’re going to do this, you have to come in every 24 days and remove that comb because if you don’t do it on day 24, you’ve just excelerated the number of mites. We developed a 2 tower system to help alleviate excuses of not taking out the comb in extreme conditions. They are two full blown colonies with a queen with a flush queen excluders and honey supers. The great thing about this is it had exactly the same advantages of a double queen system: you actually produce 30% more honey so you have a 2 queen system. I will say that one of the problems we had with this is if one of these sides goes queenless, they didn’t replace the queen. But, these bees would take a care of this comb. We’ve basically bought more time by using the drone brood treatment, it didn’t allow you to forego it.

Experimentally, small cell size doesn’t work. The epidemiological data suggest no significance. There’s no validity across regions, as well.

This is the long term solution: we need mites that are resistant to bees. We’ve got different types of bees, Russian, vas, buck fast, but one of the big problems is we see these landmines where we see these populations spreading. When you’re breeding bees, something important to remember is that you’re breeding only one generation of them. How many generations of mites are there? Lots. There are populations where we find resistant bees like in the Araknot forest in NY, you see colonies of bees in trees and they’re doing fine without mites. But, they’re in isolation because they’re 3 kilometers away from any of the other colonies, which means that if the mites kill the colony, they kill themselves. Those mites are less virulent. They’re not having as many kids and so in many cases these resistant stocks are in fact simply because the mites are less virulent than not. Having said that, I would certainly be using those stocks less than 10% than survey participants are, but we don’t see a lot of evidence are doing better than not. One thing we do find in some year s is that the people who use one type of bee do better than those who different types in their apiary. That goes to the idea of consistency where you want all the bees in your population to be the same size. It’s much more amenable to management. I don’t think they work on their own. They really own work in isolation and when you have control on those landmines invading.