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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?


TESTING

testing with sticky boards 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.

Sugar shake of quad packs

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 quicker.  

However, we are still open to finding a better way to identify breeding stock that can co-exist with varroa mites.
   


BREEDING

Pre Varroa Breeding

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 Russian Queen 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.


TREATMENT


We are evaluating some different methods of control.

Management Techniques

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.

Single storey hives

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.

Limiting drone cell in brood nest

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.

Drone catch


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.


Medication

Organic/Soft chemical treatments (organic compounds in food already)


Icing sugar dusting

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.

Oxalic acid sugar syrup drizzle

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.
 
Formic acid

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 helped 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.

During the 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:

  1. Change entries on hives from top to bottom early - before the bees are flying.  The application of formic acid requires a change from the top entrance to the bottom entrance.  This results in a lot of early drift, weakening some hives and over-populating others.  In the spring of 2013, we changed the entrances as soon as we uncovered them from the snow.  There has been less drift and it didn't seem to hurt the hives.
  2. Keep or move the cluster to one side of the hive.  Apply formic to the other side.  Formic can be hard on brood and queens.  This practice has lowered the damage.
  3. Two year old queens are more likely to be killed by formic acid than a young queen.  In 2011, we killed many of our chosen breeder queens because we didn't know this.  Double check that all the bottom entries are fully open (free of debris).  A one year old queen may survive a partially blocked entrance, but a two year old queen will not.
  4. Formic acid treatment is finished in less calendar time than a synthetic chemical treatment making it an attractive spring treatment for a late spring.  
  5. Formic acid has delayed spring build up in our hives.  We have begun to wonder if we should be feeding our hives at the same time we apply formic acid.  Usually, we have not needed to spring feed.  They have lots of feed and access to early flowers for stimulation.  However, we realized that spring feeding was probably standard practice where formic was developed.  They may not have realized that it could be a variable.  Also a few cold slow springs have limited the access our bees have had to continual spring flower stimulation.

Thymol

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.

  
Chemical


Apistan (Fluvalinate)

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.

Apivar (Amitraz)

We used Apivar for the first time in the fall of 2015.  It achieved a good level of control, but the next spring we were surprised to find that the hives still met the economic threshold needing treatment.  We found out that Apivar works far better as a spring treatment and might not have done the job as well if the fall had gotten too cold too soon.  We were also frustrated by having to adjust the spacing of the combs to accomodate the strips.  We had more wax to clean off the combs next spring.  Finally, we are limited to treating 100 hives/day/person by the label, which means that Apivar takes longer to apply than some of the other treatments.  We will continue to use Apivar as one of the tools to manage Varroa mites and 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.


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