Small cell size important in breeding Varroa resistance

After reading the blogpost ”Breakthrough?” an European PhD-Scientist wrote me an email with the following comment:

After reading your post I realized that you do have small cell size, but you’re not mentioning it in the actual post. To make sure that the reader’s get the full picture, the main components of your management system, this should be explained for them.

For instance, for me it’s a fact, that the cellsize used in a selection program is a factor incorporated in the population just like springfeeding appears to create a dependency of that feed to make bees start an explosive spring behavior.

As our bees are still wild animals, you can select whatever you like (or forget to see as selection-factor) to specialize your bees. Feel very good that your selection works.

But looking at the picture I have, some more ’vitality’ comes with better Varroa control. More or less ’Race’-independent. Question for me: ’slight inbreeding effect’?”

A valuable comment which gives food for thought. Thanks!

Small cell size (SC) is so natural for me, that it’s the normal thing. I forget it sometimes. Those small quick bees flying directly into the entrance are what I expect when looking at a bee colony.

It’s interesting Eric Erickson in Tucson when he started his breeding project for Varroa resistance found that many survivors that he used in his program were on 5.1 mm cell size. This was quite smaller than the most common 5.4 mm. http://www.elgon.es/diary/?p=457

Eric_EricksonF Eric Erickson when I and Hans-Otto Johnsen visited him and Lenard Hines about ten years ago talking Varroa resistance.

Erickson is said to have been forced to retire earlier than he should have. He died earlier this year (2016) well above his 70th year. There were nice obituaries, but I couldn’t find a word about his Varroa resistance program. Strange.

Every spring since I started to take my bees down to small cell size, when I took care of the dead outs after winter I saw that many combs were poorly drawn. The bees had many times failed to follow the 4.9-pattern and drawn patches of sometimes bigger worker cells and sometimes a lot of drone cells. Also when managing struggling colonies during the season the same observation was many times made. This year very little of this was seen. But I still have some colonies that can’t follow the 4.9 pattern when drawing their own combs (but they do well on already drawn small cell combs, especially colonies with heritage from queens from other beekeepers I have found interesting to try.

At the same time I’m aware that there are beekeepers that havn’t treated against Varroa for many years that still use large cell sizes. I draw he conclusion that it is possible to keep bees on large cell size and still be treatment free. But I see very little reason for not going down in cell size. The most important reason is that the bees themselves go smaller when given the chance. It must have something to do with their fitness and survival, not actually in first place in relation to Varroa.

Concerning the earlier blog post “Breakthrough?” and that I have used very little Thymol this year. Last year at the end of July I had used Thymol on about 70% of the colonies. This year at the same time of the year I have used Thymol on 2 colonies out of about 150 (I had about 150 last year too). I find it hard to believe that the only reason would be a successful breeder queen. I think better pollen availability this year has given a better immune system. And reinvasion I think is less problematic. With the latter in mind, I can imagine that adaptation to better control the mites is developing in the bees. And the absence of chemicals, in this case thymol, do not disturb this adaptation.

Another change in management is that I don’t move bees between apiaries. When making splits they stay in the same apiary. If there’s only one colony in a yard I split that colony and build up the apiary again this way (from now on). Some minor movements of bees have been done though.

Breakthrough?

Last year I saw more wingless bees than I had expected and I used more thymol than I had expected. I realized that I could partially thank the bad weather fort thias. The bees had got too little of pollen. Their immune system was not at its peak.
It was not easy to find suitable breeder queens, ie, who showed great varroa resistance. I found a colony that had not needed varroa treatment for a few years and it had not had any wingless bees. VSH test could not be done as I found only one mite in more than 100 pupae. And this mite had no offspring. So if you would allow it to determine the VSH-level, this would be 100% VSH. However, the so-called statistical significance was non-existent because of the low number of mites (just one single one). Well, the low number of mites were decisive. S241 was last year’s most important breeder colony.
This summer, I have not seen much of mites and almost no wingless bees so far. Some odd mites in 4 colonies, of more than 140 hives. Well, those who got the most thymol last year, got Thymol in May this year and then got its Queen replaced. So that’s one explanation, about 15 colonies. A colony that was a split from one of those 15, which raised a queen of their own was the first. Due to it’s history it got Thymol as soon as I saw the wingless bee. The queen will be shifted.

A problem hive had got a daughter of S241 last year. A Beeshaker test though showed 0% varroa level. Viruses still a problem in spite of no mites? 

The other day I saw a wingless bee on the hard board in front of the entrance of a colony that had got a lot of Thymol last year. It did not get Thymol in May as it was shifting its queen in May, I found a dead virgin on the hard board and drew that conclusion. I decided to make a test with the Bee shaker due to the wingless bee. I did it yesterday, July 20, 19 mites out of minimum 300 bees , 6.3% varroa level. The hive got Thymol.

1DWV 19 mites, 6.3% Varroa level – Thymol.

Today I came to an apiary with a daughter of the 241 (introduced in 2015) which have had no need for Varroa treatment in a couple of years, neither 2014 nor 2015. This colony was now a strong colony that given a good crop. With still some time to go for eventual more honey to come.

241d No need for treatment for a couple of years (2014 and 2015) plus probably this year. Actually lower Varroa level now compared with spring ( at least not bigger).

In May, I tested interesting candidates for being breeders with the Bee shaker. This 241-daughter was among those of course. The Varroa level was 2%. I didn’t give it Thymol as this was not more than 3%. I had several colonies, including several 241-daughters, that got only a few grams of thymol in spring 2015, which showed no mites at all (zero) out of more than 300 bees. The two best with different heritage (one was a 241-daughter) I used as breeders this year.

1% 4 mites, 1,3% Varroa level now.

2% -colony I tested today July 21 regarding the Varroa level, 4 mites out of a little more than 300 bees. 1.3% infestation level. At least not higher Varroa level after 2.5 months. A strong hive that has given a good crop. The Varroa level would have been much higher if the bees could not get rid of mites themselves. This colony has thus been able to get rid of mites by themselves. What a great feeling!
Now this does probably not only depend on the queen. It was introduced to a colony that had not needed any treatment for at least a year. The worker bees might have learned the new queen’s bees some tricks how to deal with mites. It would not surprise me if there is a combination of reasons for the mite fighting ability of this colony. http://www.elgon.es/diary/?p=880 http://www.elgon.es/diary/?p=890

The Bee Shaker – where to take the sample

It has been discussed where to take the bees when making the test for infestation level of Varroa mites with the Bee Shaker. From a brood frame or just near the brood. The first week of May, I did a test with the Bee Shaker of a number of bee colonies. After that I inserted sticky boards to collect the natural downfall. This happened to coincide so that two colonies tested with the Bee Shaker also got sticky boards. The sample of bees for the Bee Shaker were taken from the middle of a the super just above the queen excluder.

Skakburksprovtagning A good compromise place to take the beesample from to the Bee Shaker is in the middle of the first super above the queen excluder. You don’t have to look for the queen. Not close to the entrance where the number of mites are fewer than average. And not far awav from the brood, when there are many honey supers. The number seems to vary more there.

Those colonies tested were choosen as I had found them to be potential breeders. The two colonies mentioned both had one (1) mite in the Bee Shaker out of about 350 bees, ie about 0.3% infestation level. Three weeks of natural downfall thereafter gave 7 mites from one and 8 from the other. The sticky boards covered almost the entire bottom. Let’s say I missed seeing two mites. If so it was thus about 0.5 mites per day.

Multiplying this figure with 120 I have heard gives a figure for the total number of mites in the colony. 0.5 x 120 = 60 mites in total then. The number of bees in the colonies were at least 30 000. But let’s say it was 30 000. Then 60/30000 would maybe give an infestation rate = 0.2%. But now I’ve seen reports that one should multiply by 30 (20-40). Then it will be completely different figures (in “favor” of the Bee Shaker). Collecting natural downfall should be done during the normal brood period, not in the very beginning or the very end of the brood season. In the case of the natural downfall of varroa mites, mites will also come from mites emerging from brood cells that have hatched during these three weeks. The natural downfall should therefore have given more mites compared with the Bee Shaker if these methods should have given corresponding figures. Therefore, the conclusion should be that the Bee Shaker revealed a greater proportion of the total number of mites in the hives than the natural downfall did.

The Bee Shaker could therefore be trusted to be an enough reliable tool to show infestation levels of Varroa mites, when samples are taken close to the brood, but not from brood frames. http://www.elgon.es/diary/?p=914

Wingless bees and varroa level

Before varroan came there could be seen occasional bees with undeveloped/deformed wings in spring. Maybe it was the influence of DWV, Deformed Wing Virus. But it may also have been chilled brood. During the final phase of the pupa development to finished bee the wings are formed. Cold nights and too much of brood could maybe have caused undeveloped wings.

Today, one can probably assume that when you see a wingless bee, it’s DWV responsible. Varroa mites are paving the way for many viruses into pupae and adult bees that had not previously bothered bees. Moreover, these viruses multiply in mites. So today mites spread viruses more efficiently than when the mite had just arrived in Europe. Why that is so is another interesting discussion that probably involves the use of miticides.

 

The Bee Shaker

The Bee Shaker is a great way to keep track of the level of mites in the bee colony, especially in spring and late summer, so the amount of virus can be kept reasonably low by allowing people to fight the mite if it exceeds a certain degree of infestation. (If that is the strategy chosen.) A good benchmark that many use today is 3%, three mites on one hundred bees (9 mites in 300 bees/1 deciliter of bees).

It also means that to develop a bee stock towards better varroa resistance, you don’t treat against the mite, especially below a mite level of 3%, whenever in the season it is measured.

But if there are wingless bees in the bee colony? It’s usually a sign of DWV and thus too many mites. Here is the Bee Shaker again a good tool, to find out if there really is a high degree of infestation of mites when you see a wingless bee. If you decide to treat against mites if the level is high you might do it to prevent the spread of mites to other colonies nearby.

 

A colony with a wingless bee

Last year’s breeder queens seem to have produced many queens that have given colonies that control the mites quite well. One of these daughter queens was introduced to a colony that had problems with mites. Perhaps the biggest problem was virus.

This colony was quite weak in this spring and developed slowly, compared to the other colonies in the apiary. I concluded that I would have to check the brood nest to find out the cause. Maybe the colony was shifting their queen?

On a later visit to the apiary about June 20, I saw one, only one, wingless live bee on the hard board in front of the entrance. I then looked in the brood nest, but saw no more wingless bees on the brood frames. But the brood frames had a so called shot gun pattern with a lot of “holes” where you would have expected capped brood as the other cells on the comb contained capped brood. Many pupae seemed to have been removed by the bees. Most likely not due to inbreeding as the queen had mated in the apiary and the number Elgon colonies in the neighborhood was quite high. No trace of any brood disease could be seen so I concluded that a likely cause could be cleaning out of varroa-infested brood. Or could the bees detect virus in the pupae and remove it, without there being a mite in the cell, and remove the pupae?

Could that be the reason why the colony developed so slowly – that the bees were throwing out mites? How had they managed? The wingless bee could indicate that they had not done so well and that the amount of mites was big. Now it was time for a Bee Shaker test to find out the level of Varroa infestation. (Here you can read more about The Bee Shaker, its uses and possibilities: http://www.elgon.es/diary/?p=809)

Here you can see a video clip when doing this test (sorry I’m talking my mother tounge Swedish):

The sample showed zero (0) mites! Then it’s no use to treat, There were far too few mites in the colony. Why had there been a wingless bee recently before the test?

VarroaVirus The brood frames looked less spotty and the colony stronger.

July 8 I was visiting the apiary again. Once again I saw a wingless bee on the hardboard. But now I knew the Varroa level was low. Still no use treating. I looked in the brood nest. The colony was a little stronger still and the brood frames had fewer “holes”. The bees look healthy. They were recovering.

Virus apparently remain in the colony for a while after mites are eradicated – by the beekeeper or the bees.