Everything Varroa

by Dennis van Engelsdrop

Part 4

Tools to Control

Let’s talk about what types of tools we have to control the mites. The mites reproduce in the brood cells and cause damage at this level, critical for the winter, and they reproduce at a rate that doubles the colony every month. We’ve seen the national averages and that over the last five years we’ve done this, the average mite load in this country come August is in excess of what we think is causing damage to colonies. The average load in September or October is well above what we think doesn’t cause damage.

Let’s talk about the Bee Informed Management Survey results. You’ll see on the graph whiskers that aren’t what you usually see as error bars on the data. These are 95% confidence intervals. If I were to sample this population again and again, that average would fall between the two lines on the chart 95% of the time. If the two lines overlap, that means that the populations are not significantly different. They’re exactly the same statistically. If they don’t overlap, we consider them significantly different. The people who reported using a known varroa mite control product lost a lot fewer colonies than those who didn’t. What’s worrying though is that 60-70% report not using a known varroa mite control product in the last 12 months. It’s useful to look at the history of treatment in Germany because they’ve been dealing with this problem for longer than we have. In 1982 when they got the varroa mites, they used a product based on fluvalinate as a treatment once a year. It stopped working by 1987 and they started using 1-2 winter treatments of coumaphos, a different, active ingredient using it twice a year, five years after the introduction. In 1995, after that didn’t work anymore, they had problems in the summer so they started using formic acid as a mid-season treatment and then using coumaphos in the winter. Today, they have to be much more aggressive with mite levels and treat more often. They use drum brood removal in the spring, two formic acids in the summer, and oxalic acid treatment in the winter. In Germany, their treatment regimes have changed dramatically.

We’ll break this down and talk about each product. On the chart we have all the known varroa mite control products: the purple is for people who use this product, the yellow is someone who used the product but not the product in question. Amatraz lost fewer colonies than those who used another product and certainly more than others.

I’ll go through each of these products and summarize them in terms of how to think about them. If we think about amatraz, cuomofos, and fluvalinate, these are our synthetic products; our hard chemicals we used first. They’re fairly safe in terms of humans because they’re lipifilic — they like fat, which means they don’t migrate into honey, they migrate into wax. But, they build up there. Then you have softer, bio-based products, like apiguard, apilifevar. These are essential oil based so they’re thimal and fumigants. We also have the organic acids: the formic acid and acelic acid. This is correlative data, which is not the same as causation. In 2013 and 2014, people who used cuomafos or fluvalinate lost the same number of colonies as those who reported not using anything at all because these two products have lost their efficacy. However, the next year 2014-2015, we did see the people who used the products lost fewer colonies than those who used nothing at all but it wasn’t different than any of the products. Our real concern is that it builds up in the wax. The bee bread that we test, not the wax, have these known miticides in them. So we’re feeding a miticides to young bees and that has negative effects on them.

Amatraz users lose fewer colonies than those who use nothing at all or use another known varroa mite control product. It’s one of the newer products on the market that has lower colony losses. Commercial beekeepers used none at all and lost about 34%, used it once and lost 30%, used it twice and lost 24%, used it three times and lost 20%, used it four times and lost 10%. To use this product four times a year is a disaster waiting to happen. If you’re going to use it more than once, you’ll want to combine it with an organic acid or an essential oil based product. Even if you kill 99% of the mites, that 1% of mites who are resistant to amatraz can be knocked out by that other product. Just using one product consistently like this is in the long term is a short sided option.

We also do mite resistance asay so if you’re part of a tech transfer team, you’ll send in your kits and we’ll check the mite levels and their susceptibility to certain products. We also do this randomly across the country. Basically, we put a handful of bees in your yard with your mites as long as they have 5 or more mites per hundred. We’ll put them in a jar with a little bit of the product, we’ll wait 6 hours, we count how many mites died, then we kill all the mites to figure out what percentage of mites died in the presence of the product. If a mite population is considered susceptible, it means that 85% of the mites die within 6 hours. We haven’t detected any populations that are truly susceptible to any of our main products, including flumethrin, which isn’t registered in the product (it’s used in Europe but it’s our out-control). We have some level of resistance. They’re not killing more than 85% of the mites. In fact true resistance is also rare. It occurs if more than 85% of the mites are surviving, we’d consider that resistant population. We have one or two colonies evidence of cuomafos or flavalinate. We have yet to find that in amatraz. However, there are a lot of beekeepers complaining about the product. They’re putting the strips in, coming back, and finding high levels of mites because there’s been a switch to a homemade formula versus these strips. The strips are much more expensive but it’s a great way to insure that you’re not getting out of the control and speed up resistance development. Use low doses of the strips. The product that stands out the most, with over 50% of detections, are the varroa sides. We’re killing an arthropod already on an arthropod. There’s no question that the presence of cuomafos, fluvalinate, and amatraz negatively affect the queens and workers. It’s a lot like chemotherapy — you don’t do it because it’s good for you, but because it’s better than the alternative. Fortunately, we do have softer, organic products like oxalic and formic acids. I would make sure that 40 days before I had the super, I would put in the finewall treatment if I had detectable levels (maybe apiguard or apiliphar). If you’re honey flow ends early, I would do another check and if I have detectable levels of three or more mites by August, I would put on a formic acid pad. I would do three treatments: essential oil, formic acid, and an oxalic treatment. There have been some complaints about formic not working: if you’re doing a mid-season formic acid when it’s really hot out, what happens when you’re putting those pads on that formic gets flashed out there, they start to work in the first 24 hours, but what happens is that it gets under the capping kills 80% of the varroa under capping. If you can damage them, that’s great because you don’t have to wait for them to come out, but it turns out that it doesn’t kill them. But, it’s damaging the hairs on it’s pedipalps, which means that the mites aren’t able to smell the right stage brood anymore. So often, your mite levels are three times higher than before you treated maybe because you have fewer percentage in the brood because you’ve damaged those adult varroa mites. Sometimes, that mite check after a formic treatment will give you a heart attack but will decrease 2 weeks after. My personal preference would be the thimble, formic, and drip oxalic when it’s broodless.

We’ve talked about these organic acids and essential oils as if they’re somehow better for the bees than the synthetics. They may be better but nothing is free. We wanted to treat colonies that didn’t have any mites and then look at the expression of different stress bees to see if the treatments themselves had immeasurable effect on the stress of the bees. The answer yes. And that’s true for cuomafos, amatraz, formic acid, and thimal. If we can slow the population growth down, it means we have more time for intervention. If we can get to three mites per hundred by October rather than September, it gives us more time because we want to keep our honey supers on, which means more honey, but we have to take them off to put the treatments on. There are different methods to stretch that time period. One is this new product that prevents the invasion of mites into the colony from your neighbor. They’ll be these varroa gates that the bees will have to crawl through. It’ll be a treated strip.