Varroa: A Personal History
After 50 years as a commercial beekeeper, both with his family’s business, Arataki Honey, and his own Berry Beekeeping, respected Hawke’s Bay apiarist John Berry has wound back to 24 hives for the coming season. His beekeeping will take a more research-centric approach as he aims to further give back to the industry he has been a part of for so long. Top of the research priorities? Varroa destructor, which he has battled for over 20 years now. This is his history, in his words, with the vicious honey bee parasite.
By John Berry
Varroa was first discovered in New Zealand on April 11, 2000, in South Auckland.
Its discovery caused a huge shock to all those involved with or dependent on bees. A huge amount of time was put into the problem by both the Ministry for Agriculture and Fisheries (MAF) and beekeepers, with many putting in huge hours doing delimiting surveys, and on July 12 the government decided not to target eradication, but instead to try and slow varroa’s spread.
The inevitable spread
Movement controls were put in place that restricted the movement of hives. These restrictions did slow the spread within the North Island and to the South Island, but ultimately varroa spread like everyone knew it would. We first detected it in our own hives on December 20, 2003, in an area where we would have expected to find it from natural spread. That autumn we treated every hive we had, regardless of whether they showed signs or not. By the next season it had pretty much spread to every hive we had.
The cost of eradication was estimated at $55-70million, whereas the cost to New Zealand of varroa was estimated at $400-900 million over the following 35 years. My personal guess would be it’s currently costing between 30 and $50 million a year.
The Minister for Biosecurity at the time, Marian Hobbs, believed that the incursion was caused by the illegal importation of queen bees and this was widely believed within government circles. I believe this had some impact on the decision not to target eradication. Most beekeepers did not believe it came from illegal imports. If it had come from illegal imports (or a swarm) then you would have expected both European foul brood and tracheal mite to arrive at the same time. Although, to be fair, chalk brood was almost certainly brought into New Zealand with the illegal importation of Caucasian bees and we didn’t get tracheal mite from that importation. Even today New Zealand’s beekeeping industry is still quite a small closed group and I have never heard any rumours associating anyone with illegal imports at that time, whereas it is general knowledge in the beekeeping community who was responsible for the illegal importation of Caucasian bees.
The Ministry for Agriculture and Forestry also believed that varroa had been in New Zealand for up to five years, which I find very hard to believe as we quickly found out that hives would go from clean to dead within 12 months at the most. Personally, I think it quite likely came in on a florist’s flower and a very unlucky bee took it home.
When we first heard about varroa my brother and I considered our options. One of those was to extract every ounce of honey and then gas the bees, press out all the wax and then find another job. I will always be grateful for the movement controls and the help and knowledge that was freely given by beekeepers who had already had to deal with varroa for a few years. When it came time for our turn, if we hadn’t had that knowledge, we would have lost a lot of hives in a very steep learning curve. As it was, with their help, we lost very few hives and, while we didn’t always get it right, most of the time we managed pretty well with varroa.
Aiding us were increasing honey prices and, surprisingly, increased honey crops (less competition from feral hives). Overall, our 10-year average had increased by 10kg/hive 10 years after varroa arrived. In one area where there had been a lot of feral hives the average per-hive increased by 20kg in the same period. Varroa certainly brought the beekeeping industry together in a way that I’ve never seen before – and certainly never seen since. Branch meetings were huge and attended by not only beekeepers, but also orchardists and farmers concerned about the future.
Our bee scientists also worked long hours trying to work out answers to the problem and pass them on to the beekeepers. Many beekeepers, including myself, helped with trials using various treatments. I learned a lot working with Michelle Taylor and Dr Mark Goodwin and there were a lot of other people doing good work.
One advantage New Zealand had was that many other countries had already suffered this fate and treatments were already available. We also knew exactly what would happen if we misused the varroa treatment products we had available, but unfortunately – and I believe stupidly – no controls were placed on the use of these products, other than having to follow the recommendations of the manufacturers and even those were never enforced.
At the time I was helping out with AP2 work for the American Foulbrood Management Agency and I frequently came across hives that had several years’ worth of strips in them. It also came as no surprise to me that the area that I first saw resistance to synthetic pyrethroids was next door to a beekeeper who did not alternate treatments for over 10 years. Those beekeepers that wished to use “alternative” treatments should have been allowed to, but all those using the so-called conventional treatments should have had to treat their hives within certain timeframes, both spring and autumn, so that all hives in an area overlapped in their treatment times. Further to that, they should have had to supply proof that the treatments had been taken out. Alternating treatments, spring and autumn, should have been compulsory and the same for all beekeepers.
Treatments were always going to fail
We knew this, or at least anybody that studied what had already happened overseas knew this, and we also knew that, as time went by, it would take less and less varroa to kill a hive. We could have perhaps delayed this for several more decades. However, despite lobbying from the scientific community, no controls were put in place that could have helped extend the effectiveness of treatments and funding was not ongoing for the only other alternative, which is varroa tolerant bees.
I was one of the very few, at the time, who advocated for eradication. I believed then and I believe now that, even if we had to kill every hive in the North Island, it would have been worth it in the long run. Time has proven me right and we are now in a situation where synthetic pyrethroids no longer provide adequate control in some areas and, even when treatments do work, the viruses spread by the varroa are still killing hives.
This autumn I have experienced this phenomenon myself for the first time and it’s plain frightening. The previous autumn I heard of massive hive losses in some areas and put it down to resistant varroa but, having seen what I have seen this autumn, I’m now certain that in a lot of cases the treatments did kill the varroa. This autumn I have seen hives at treatment time with what I would have considered light to moderate levels of varroa collapse and die despite the fact they had few or no varroa left in them. Many other hives went from two boxes of bees with plenty of brood down to two or three frames of bees and only showed signs of recovery after two months of treatment.
To when we first got varroa… Synthetic pyrethroids would clean out varroa ‘just like that’. Hives that had really bad parasitic mite syndrome would be looking much improved within a couple of weeks of treatment and would normally survive fine. I also found that amitraz worked well but, while it too had a quick knockdown, a few varroa always seem to survive for quite a while and a 10-week treatment was necessary. Provided you got your hives treated at the right time, apart from being an expense and a lot of extra work, varroa was not the end of the world.
Every year varroa has got just that little bit worse. Every year a higher percentage of queens fail for no good reason. Every year I have wondered whether what I have done in the past would still work.
While we had a temporary increase in production, the feral hives were soon replaced by a huge increase in beekeepers and beehives. It was also not possible to run as many hives as we used to because of the extra workload from varroa and the importance of treating hives in a timely manner.
Alternate treatments to synthetics
I have, over the years, experimented with most of the alternative treatments. Thymol based products, of which there are quite a few, do kill mites and sometimes even a reasonably large percentage of mites. However, they are not always reliable and I found they seem to disrupt the hive considerably.
Oxalic acid dribbles and oxalic fogging appear to be reasonably effective, but only when there is no brood in the hive. Oxalic acid/glycerine strips are reputed to be effective, but when I have used them I found that, while they caused no harm to the hive, they also did very little good. I had high hopes for these strips but I cannot get them to work.
Food-grade mineral oil, both as a fog or in coils may be a useful carrier for some substances, but on its own is useless snake oil in my experience.
Formic acid is something I have used very little because I just think it’s dangerous for both the user and the bees. It does however work, but expect to lose some bees which will come as no surprise when you see that it burns the grass outside the hive entrance.
Drone brood trapping is an effective way to slow down the build-up of varroa, but is labour-intensive and if you are a few days late it’s worse than if you never tried in the first place.
Varroa tolerant bees have been bred in New Zealand but it is not simple and offspring, even from 100% tolerant queens, have very varied tolerance. If every beekeeper in New Zealand selected for this trait we might get somewhere but, 20 years on from varroa getting here, I haven’t seen any evidence of tolerance in the general bee population.
We need to remember that what works overseas will not always be as effective here, because we have a very long breeding season and some areas have no broodless period at all.
I have, until this year, got away with a spring and autumn treatment (except for the first year when reinvasion was horrendous). Some people will still get away with this, but many will not and I absolutely believe that, to be safe, it is now necessary to treat hives at least three times per year.
Things may have been worse than normal for me this autumn because there has been no honey flow for months and it has been one of the worst autumns I can remember, but I have seen plenty of bad years without this sort of hive collapse happening.
I’m fairly sure I could keep a few hives at home using a combination of drone brood trapping and periodically caging queens to create an artificial broodless period and then treating with oxalic acid dribble. I may also use formic although, like I said before, I don’t like the stuff.
What commercial beekeepers are going to do I have no idea, but whatever they do has to be viable both economically and timewise. We have to remember that what may have worked in the past may no longer work, because of both resistance and the simple fact that it takes a lot less varroa to do damage. Therefore, treatments have to be very effective to work.
There are a few glimmers of hope on the horizon, but they are by no means certain. We live in a time where our wonderful scientists have to study what they are paid to study rather than what is needed and MPI seem to be totally oblivious to a threat that will not only cripple New Zealand beekeeping, but also those that depend on bees for pollination. There are still plenty of beekeepers out there that have not yet experienced what I, and many others, have experienced and many of them are denying there is a problem.
There is a problem and it’s coming your way...
I am taking the easy way out and retiring, although I will keep some hives for experimental purposes because I not only want to beat varroa, I want to help others beat it as well.
I hate ending this on a pessimistic note, but I can’t help wondering what would have happened to my varroa weakened hives this year if we also had European foulbrood or, probably worse, small hive beetle.
One problem at a time though huh?...