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FINDING OUR WAY WITH VARROA MITES
We had tested 25% of our hives every year for varroa mites. In the spring of 2008 we found our first varroa mites in 3 yards. By fall they had spread, but not to a level that we felt it was necessary to treat. We have since tried several methods of monitoring and control. The following article breaks it into testing, breeding and treatment. Some we’ve liked, some could only be described as duds and some of them the jury is still out. What is clear is that our beekeeping will never be the same. We expect varroa mites to occupy most of our experimentation in the coming years. We have been told that it is not our responsibility to do the research, but we totally disagree with that. Who is better than us to figure out what works with our particular bees and mites in our particular area and climate?
24 hour Apistan/sticky board test
Originally we used the 24 hour Apistan/sticky board test on 25% of our hives every spring. In 2008 we found varroa mites in 3 yards (one yard was 1 mite on one board) by this method. It caught the mites at the beginning so that we were not surprised.
24 hour natural drop sticky board test
In the fall of
2008, we used the 24 hour natural drop sticky boards to monitor our mite
levels. Not surprisingly our drone mother yard showed the most
increase, but even it did not show levels necessary to treat.
In the fall of 2010 we used a 24 hour natural drop sticky board test on every hive. It is quick to do with screened bottom boards. Slide the board in and then slide the board out the next day. All the testing was done in two days. All the boards were labelled so that they could be read during off hours or poor weather. An obvious disadvantage from the beginning was the extra two trips to each yard. The bigger disadvantage was that they were more difficult to read which limited who could do it and therefore took a very long time to read samples. We did some alcohol washes too, to see whether the results on the same hives differed. Without the statistical ability to make this claim, we could see no significant difference.
In the spring of 2009 we used the sugar shake of quad pack hives in our yard. It took a long time during beekeeping weather, was not accurate, and gave us no real useable information. The mites did not come off the bees readily and impatience led to not having accurate counts. The so called advantage of using a sugar shake is that you don't kill the bees, but no one has actually followed those bees to prove that claim. In the end it didn’t matter. While a quad pack may give you information as to whether the yard is at a high enough level to medicate, it gave no relevant breeding data.
Alcohol wash of every hive
In the spring of 2010 we started using an alcohol wash on every hive. It was quick to do in the yard. We labelled the samples with the hive numbers and brought them in to read when the weather wasn’t nice enough to work with the bees. While it took a long time to read that many samples, it gave us useable breeding data. They are simple samples to read so we used all of our employees to get through the backlog. We found a couple of queens in the early samples so then we changed the procedure to either find the queen first or shake the bees on our queen finding excluder tub before it went into the sample jar. In 2012-2013 we switched to sampling every hive with a two year old queen that might be bred from and otherwise tested quad packs to determine treatment. Even though the sampling is quick and easy, the reading of so many samples gets old quickly.
|Therefore, right now our choice
of test is the alcohol wash. Since everyone can read the samples
during poor beekeeping weather, it allows us to get through the samples
However, we are still open to finding a better way to identify breeding stock that can co-exist with varroa mites.
In preparation for varroa we obtained and maintained a few purebred Russian lines of queens in isolation mating yards. We also open mated all of our stock with predominately Russian stock.
Russian Bee Stock
Dr. Thomas E. Rinderer, head researcher at the USDA's Agricultural Research Services, Honey Bee Breeding, Genetics and Physiology Lab in Baton Rouge, Dr. Robert Danaka, an entomologist, and Dr. Gary Delate, a technician initiated the research project to evaluate honey bees from the Primorsky region of eastern Russia for varroa mite resistance. The honey bees in the region had been living with varroa mites since at least 1952 and it was believed that they might be able to tolerate the varroa mite. In the fall of 1994, a preliminary fact finding mission determined that there was enough evidence and scientific support to initiate the project. In June of 1995, a test apiary was established in Primorsky. Queens from 16 separate beekeepers in Primorsky were collected and brought to the Honey Bee Quarantine Station at Grand Terre Island, Louisiana in 1997. In 1998, daughters were raised from the queens and mated to drones from the Russian queens. The evaluation continued in secure apiaries near Baton Rouge.
In 2000, Dr. Medhat Nasr in conjuction with the Ontario Beekeepers Association and the Saskatchewan Beekeepers Association, bought some Russian stock representing 3 lines from Baton Rouge. The queens were placed in apiaries in New York state to produce drones for semen collection. In late August and September, eggs and semen from the queens were imported to Smithville, Ontario. The result was some pure Russian stock and some cross mated Russian stock to Canadian stock. In 2001, larvae from the Ontario stock was raised into queens in Saskatchewan.
Pedersen Apiaries was chosen as one of 3 beekeepers in Saskatchewan and 6 beekeepers across Canada to evaluate Russian Bee Stock on varroa mite resistance, honey production, winterability, spring build up, swarming, supersedure, agressiveness and tracheal mite resistance. The Russian queens we raised were put into yards with queens of our own stock and of the same age. Unfortunately, we did not keep a pure line of our own original stock, but instead open mated our queens to the Russian stock. Therefore, it has been difficult to evaluate differences. We dropped the pure Russian lines in 2010 when we could evaluate hives according to mite levels and breed accordingly. We have not noticed any significant differences in honey production, winterability or spring build up. We have noticed an increase in chalkbrood in the Russian stock. We have noticed an overall increase in the agressive temperment of our bees. The pure Russian lines seemed to be even more agressive than our hybrid stock. However after so many years we seem to have gotten it under control again.
Post Varroa Breeding
In 2009, we designated
3 of our best yards, or about 150 hives, as hives that we would not treat
with either drone catch or medication. We planned to instead breed
off of their survivor stock. To manage the economic risk of this
strategy we planned to treat our other hives. During the winter
of 2009-2010, we experienced higher than normal winter losses
in all of our hives. Therefore, we abandoned this particular
experiment until we recovered our numbers. Unfortunately, due to
other circumstances we have downsized our total operation and no longer
have enough hives to have a significant sample size with which to
conduct this kind of breeding.
We abandoned the isolated
mating yards in which we bred pure Russian lines in 2010. The extra
cost was not justified when we could instead test every hive and breed from
those with low varroa mite levels. Now we breed from 2 year old queens
with low varroa counts in the fall and above average honey production.
Screened Bottom Boards
As a pre-emptory mechanical
method to control varroa mites, we built screened bottom boards for about
1/4 of our hives during the winter of 2007 – 2008. We planned to have
screened bottom boards on all of our hives by 2012. Instead, with the
advent of varroa, all of our regular hives had screened bottom boards by
the 2009 season. We do not have the capacity to test how effective they are
in controlling varroa mites. However, it makes sense to us to provide
the opportunity for the mites to fall through the bottom board to the
pallet below rather than having them waiting on the bottom board for the
next bee that comes along. What is certain is that fewer bees from
the hive have to work at keeping the bottom board clean. Garbage does
fall through and they don’t bother to clean it up. During the winter,
we close off the screened bottom boards with corraguated plastic. During
the summer we
need to block the area between the hive and the pallet to prevent bees from
clustering under the screened bottom board when they are crowded because
that defeats the purpose of the screened bottom board.
There had been a question as to whether during the winter of 2009 – 2010, open screened bottom boards may have aggravated our winter losses. Therefore, we tried using our old non-screened bottom boards on half the hives in some yards. The only noticiable difference between hives on normal bottom boards versus those on screened bottom boards was that hives with screened bottom boards had fewer moldy combs.
Before and after we got varroa mites we were told that single storey hives were a good mechanical method for working with and dealing with varroa mites. We were told they were easier to treat because the cluster was not divided and they had fewer combs and distance for the mites to fall. We were glad to hear this because we use single storey hives. It seems to make sense that they would work well in conjunction with screened bottom boards.
It is well documented that varroa mites prefer drone brood and produce more offspring in drone brood. Our drone mother hives, only rivalled by our cell builder hives, increase their mite loads faster than our normal hives. It has been a longstanding honey producing strategy to limit the drone cell in the brood nests of our normal hives to less than 1% so that we produce workers rather than drones. This too makes sense that it would limit the population growth of mites in our hives. We have been told that all that does is ensure that the varroa reproduce in the worker cells injuring the workers instead, but fewer mites should also result in fewer injured workers. In the end, do more mites or limiting drone cell result in more injured workers? We do not have the capacity to answer this question. However, we do believe that this strategy is impacting our mite levels since they do not seem to multiply at the rates that we have been told to expect.
Starting in the summer of 2009, we used one round of plastic foundation drone combs in the brood nest to capture varroa mites. That first summer we found it time consuming to clean off those plastic frames. Therefore, we started experimenting with empty frames with a couple of wooden cross bars in which they can build their own foundation. This was much easier to clean up and so we abandoned the plastic drone combs except for raising drones in the queen yards. Every hive has had a drone catch comb inserted and removed every year. We do not find that this is any more time consuming than putting in strips. We put an empty comb in while we are pulling another comb out to start or boost our started hives. We plan to continue this practice.
We think, but have no capacity to test the theory, that drone catch works better when it is combined with limiting drone cells in the brood nest. The bees want to build the burr comb and the foundation to drone cell and the mites prefer those spots because there is not other drone comb to choose. We then cut out the capped burr comb and remove the capped drone catch comb.
We had problems trying
to get rid of the drone catch that we cut out. We do not have enough
freezer space to freeze all the combs and we cannot justify the energy
to increase our freezer space. The energy used to melt the wax
was not justified in the wax obtained. We didn’t want to leave them
outside for other bees to investigate and potentially carry varroa mites
to their hives. Having them hatch inside a warm space where the
mites can be contained made a huge mess to clean up. We considered
burying them, but that is a lot of work. We finally discovered that
our neighbour’s pigs love to eat them.
|We plan to continue using all
of these management techniques, including screened bottom boards, single storey
hives, limiting drone cell in the brood nest and drone catch. They
may not reduce the mites a lot, but every little bit helps.
In 2009, we used icing sugar dusting on 5 frame nucs that had been started from the cell builders hives. It was honey season so we did not want to use anything that had the potential to get into the honey. We tried several methods of application including a Glory Bee duster and a bee brush. It was time consuming, difficult to do, and did not seem to have any effect. Like using icing sugar to test for mites, we do not plan to use icing sugar dusting again.
In 2009, we used a fall oxalic acid sugar syrup drizzle application in the hives that were not designated for the post varroa breeding project. In the spring of 2010, those hives did have significantly fewer mites than the hives we did not treat.
We chose to use the
sugar syrup drizzle method instead of the vapourization method because
it is safer for humans and because it seemed to us that it would take
less time. Our hives are well sealed except for the screened bottom
board and entrance, but even then it seemed like it would be very time
consuming to seal the hive and wait 2 minutes/hive for the vapourization
to take place. We started using an Optimiser to treat the hives.
The Optimiser just didn’t have the capacity to do the number of hives that
we needed to do in the day. It jammed in the yard and would have to be brought
home for service. Therefore, we have bought cheap veterinary syringes
to use. They work great, though we found that you have to get fresh
ones each year to deliver a smooth quick application.
|So far this is our favourite
method of medication. We have used it every fall after they stopped
raising brood. It is cheap, quick, safe and seems to work. The
treatment method does not remain to get in the way or have to be removed
and reapplied the next time you work the hive.
We first tried
formic acid in the spring of 2010 on a few hives. Many of the
hives that spring were too weak to use it. Until
2014, we used it as a spring treatment. We first used
Mite Away II and then moved on to using Mite Wipes soaked in formic
acid applied every 4 days. So far we have
a love-hate relationship with formic acid. Mite Away II clearly
to keep our mite levels down, but its use has also harmed our
hives. It's irrelevant because Mite Away II is no longer
available. We are not convinced that Mite Wipes applied every 4
days is effective, but
it is extremely time consuming and expensive.
spring of 2014, we bought some Mite Away Quick Strips (MAQS) to try on
some of our hives. They were difficult to source because we were
too small to get them directly and too large to get them from suppliers
who were used to supplying hobbyists. Our regular suppliers do
not carry them. We found a supplier, but we had to order them
ahead. In the end, we did not use them because our hives were not
close to the economic threshold for Varroa Mites. They had
expired by the time our hives were at an economic threshold. We
would like to try them, but we cannot stop thinking that we can't
afford to buy them to not use them, but we cannot wait to order them
until we have done the sampling. It's a conondrom.
Lessons Learned Using Formic Acid:
We tried Thymol
in the form of Thymovar for the first time in a few yards during the
spring of 2015. It was easy to use, however it did not knock back
the mites much if at all. We will try it again, but this time in
a fall application. We are not convinced that we have a long
enough window in the spring before putting honey supers on that meets
the temperature requirements of Thymol.
We used Apistan for 24 hours in 25% of our hives in the spring for approximately 10-15 years before 2008 to test for mites. In the spring of 2010, the fall of 2013 and the spring of 2016 we treated our hives with Apistan. There is no evidence of resistance to Apistan in the mites following those treatments. The next time that we need to use a chemical control we will consider Apivar to ward off mite resistance.
|Our current plan is to incorporate
varroa mite control into our overall philosophy on treatment of all diseases
and pests. That philosophy is to monitor the disease or pest,
breed for resistance, use mechanical methods of control, and finally
use chemical treatments as a last line of defence when necessary.
We will continue to consider and try management and treatment options
until we find methods that work for us.
Revised: March 17, 2017.
Copyright © 2002 Pedersen Apiaries. All rights reserved.
Original Design & Graphics by Karen Pedersen
Photographic images are under copyright and used with permission of John Pedersen or Karen Pedersen