# Resistance to varroa : what mechanisms?



## Snowhitsky (Mar 1, 2014)

What I'd like to know is the influence of hive continuity over pure genetics on VSH. In other words, how important is the influence of older bees passing on VSH traits to younger bees as opposed to those traits being inherited.

For example, has anyone tried requeening existing VSH hives and non-VSH hives with II VSH sister queens? If it's a purely inherited trait then the non-VSH hives should become VSH once the adult bee population is replaced with the VSH queen's offspring and within a couple of months both sets of hives should be exhibiting similar levels of VSH behaviour.

I'd be grateful if someone could point me to research on this aspect.


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## mike bispham (May 23, 2009)

Snowhitsky said:


> What I'd like to know is the influence of hive continuity over pure genetics on VSH. In other words, how important is the influence of older bees passing on VSH traits to younger bees as opposed to those traits being inherited.
> 
> For example, has anyone tried requeening existing VSH hives and non-VSH hives with II VSH sister queens? If it's a purely inherited trait then the non-VSH hives should become VSH once the adult bee population is replaced with the VSH queen's offspring and within a couple of months both sets of hives should be exhibiting similar levels of VSH behaviour.
> 
> I'd be grateful if someone could point me to research on this aspect.


I think its broadly understood that traits are inherited, not taught.

Thanks Eduardo. For those short on time, the conclusion is:

"In conclusion, this study presents colony level
characteristics in a population of surviving
honey bee colonies that limit the mite
population growth by either suppressing mite
reproductive success or limiting mite reproductive
opportunities by reduced brood production.
Although the exact mechanisms
behind these traits are not yet identified, the
information collected from this investigation
is a step forward towards understanding the
adaptive processes of mite tolerance in honey
bee colonies. The only documented sustainable
tolerance to V. destructor mite in European honey
bees are of colonies that have not been selected
by humans but that have been exposed to natural
selection pressures."

I'm not sure if that 'only documented' still stands up, or if the reason for it is lack of documentation of private beekeepers - who can't be documented. 

Mike (UK)


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## Eduardo Gomes (Nov 10, 2014)

Snowhitsky said:


> I'd be grateful if someone could point me to research on this aspect.


Snow, if I understand well your question in principle two sisters artificially inseminated with identical semen theirs offspring should present a very similar behavior with regard to VSH behavior. But it is a speculation, I don' t know no experimental design to test directly the issue. Already in VSH sisters mated outdoors the differences can be huge. View Erik Osterlund (POV in Beesource).

However Randy Oliver talking about the effectiveness of this behavior (varroa tolerance) he said that this behavior can be seriously compromised by the very conditions/ context of the apiary. Listen here http://kiwimana.co.nz/randy-oliver-from-scientific-beekeeping-km061/ from 38:55. As he says the answers to these and other questions about bees are anything but simple.


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## Snowhitsky (Mar 1, 2014)

You understood me perfectly. I wonder if everybody is going down the genetics line simply because most competent beekeepers can attempt to select for genes and other potential solutions are much harder to investigate. 

In everyday life we often approach problems by well-trodden routes because they work but also out of convenience/laziness. I've worked in quite varied sectors and as the complete beginner I've sometimes changed working practices by asking apparently "stupid" questions.

I suspect I'm barking up the wrong tree on this one but hey you never know!


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## Michael Bush (Aug 2, 2002)

My guess is it's a combination and testing for that would be difficult. But here are a few:

Male survivorship:
http://www.apidologie.org/index.php...29&url=/articles/apido/pdf/2002/01/Martin.pdf

Shortened pupation:
http://www.ingentaconnect.com/content/esa/aesa/1986/00000079/00000005/art00007
http://www.sciencedirect.com/science/article/pii/S0304380001004409

General Hygienic behavior:
http://www.apidologie.org/index.php...04/Apidologie_0044-8435_1996_27_4_ART0007.pdf

Varroa specific Hygienic behavior aka VSH:
http://herman.marc.usda.gov/SP2User...arris--Bees with Varroa Sensitive Hygiene.pdf

Grooming behavior:
http://www.sciencedirect.com/science/article/pii/002220118790125X
https://hal.archives-ouvertes.fr/file/index/docid/891574/filename/hal-00891574.pdf

Biting mites (specific grooming behavior):
http://www.beesource.com/point-of-view/erik-osterlund/bees-biting-mites/
https://hal.archives-ouvertes.fr/file/index/docid/891574/filename/hal-00891574.pdf
http://www.annualreviews.org/doi/abs/10.1146/annurev.ento.49.061802.123155
http://www.apidologie.org/index.php...02/Apidologie_0044-8435_1992_23_2_ART0010.pdf
http://onlinelibrary.wiley.com/doi/...sCustomisedMessage=&userIsAuthenticated=false

Producing Varroa-Tolerant Honey Bees from Locally Adapted Stock: A Recipe
http://www.beesource.com/resources/...ney-bees-from-locally-adapted-stock-a-recipe/


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## mbc (Mar 22, 2014)

mike bispham said:


> Thanks Eduardo. For those short on time, the conclusion is:
> Mike (UK)


I read that (interesting study, thanks Eduardo) and thought the conclusion would be right up your street Mike, broad spectrum colony traits providing the resistance rather than specific vhs(or other) mechanisms. Seems more achievable by your low tech husbandry approach.


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## mike bispham (May 23, 2009)

Snowhitsky said:


> You understood me perfectly. I wonder if everybody is going down the genetics line simply because most competent beekeepers can attempt to select for genes and other potential solutions are much harder to investigate.


I think mostly people go down the genetic line because both thousands of years of empirical evidence and the entire body of modern husbandry understanding both indicate clearly that... the more genetics are neglected, the more problems tend to increase; and vice versa. 

Husbandry is about controlling genetics. Period.

Mike (UK)


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## Brandy (Dec 3, 2005)

I thought this interesting since many of their conclusions come from the % of fertile to infertile etc...

"In the surviving population, a total of 614 cells were examined in 23 colonies, and a total of 592
cells were examined in the 21 control colonies with observations between ten and 35 cells per colony" 

That doesn't sound like a very large sample group to me within each colony.. I think even the pin prick, triangle sample is at least 100 cells.


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## Eduardo Gomes (Nov 10, 2014)

Brandy said:


> I think even the pin prick, triangle sample is at least 100 cells.


I'm not a statistician , but I think there are statistical procedures robust enough to deal with small samples. I hope that was the case. Peer review is usually attentive these failures. But I am no expert I repeat.

"_A highly significant difference was observed in the average proportions of successfully reproducing Varroa mites between the surviving colonies 0.48±0.02 (x SE, n=23) and the control colonies 0.78±0.02 (x SE, n=21, F1, 41.4 =75.78, P<0.0001)._" p. 537


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## Brandy (Dec 3, 2005)

This was another study done here where they used 200 cells etc...

http://www.ars.usda.gov/SP2UserFile...9-Villa--Simplified methods of evaluating.pdf


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## Eduardo Gomes (Nov 10, 2014)

Brandy I'm confused about the rationale that you are following. In the study of colonies in Gotland , Sweden were analysed a little over 1200 cells to reach conclusions. The study you shows have been analysed, if I not misinterpreted, in a first trial 100 cells, 200 cells in the second trial and, in a third trial, 100 cells. Conclusions are reached from a total of 400 cells. What you draw from these figures about the credibility of both studies? If you can help me better understand your reasoning...


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## Eduardo Gomes (Nov 10, 2014)

Michael Bush said:


> Producing Varroa-Tolerant Honey Bees from Locally Adapted Stock: A Recipe
> http://www.beesource.com/resources/...ney-bees-from-locally-adapted-stock-a-recipe/


Thank you Michael Bush. A very practical recipe that illuminates me the way to get ahead in my project bees resistant/tolerant to varroa.
The latest data are from 2000. Are there more recent data and a follow-up?


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## Brandy (Dec 3, 2005)

In the section on "Suppression of mite reproductive success" they talk about how they measured mite reproduction and it's success or failure. They mentioned "In the surviving population, a total of 614 cells were examined in 23 colonies, and a total of 592
cells were examined in the 21 control colonies with observations between ten and 35 cells per colony."

I merely mentioned and thought that most of the studies I've seen use a greater number of cells as a sample group. I'm not a statistician either but 35 cells out of a frame with potentially 3500 cells on one side seemed small. 

The other study I mentioned used a few more. I think we're all just trying to understand/verify what will give us an accurate reading when we apply some of these tests to our own colonies..


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## Eduardo Gomes (Nov 10, 2014)

Brandy said:


> I think we're all just trying to understand/verify what will give us an accurate reading when we apply some of these tests to our own colonies..


Yes I get it the pragmatic goal you seek. 

The collection procedure in the Swedish colonies is described below:
"_Complete mite families from single-mother mite-infested cells were removed using a fine brush and examined under a stereo microscope. Within each pupal cell, the following information was collected:
1. Whether the mother mite reproduced; 2. The total number of offspring per mother mite, 3. Whether an alive male was present or absent, 4. The number of dead mite progeny, and 5. The developmental stage of each individual mite offspring._" pg. 536.

This procedure is not practical for the beekeeper .
In my opinion we should look to a level above this , the colony level and the visible manifestations of varroa and / or counting of mites by convencional methods.
As for the total sample of cells analysed in both studies, the Swedish study is 3 times higher. In this respect we have different opinions.


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## Fusion_power (Jan 14, 2005)

I am seeing evidence of accumulation of multiple small genetic effects that result in gradually increasing mite tolerance. This is accompanied by ongoing attrition as susceptible stocks are wiped out year after year. The way to keep this going is to produce large numbers of colonies, let mites destroy the susceptible as fast as possible, and breed from the resistant colonies. Guess what treating for mites prevents?

IMO, it would be counterproductive to focus entirely on one trait such as VSH when other traits such as mite entombment are available and effective. We should be working on bees that combine as many resistance traits as possible, caveat that some may be mutually exclusive.


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## Eduardo Gomes (Nov 10, 2014)

Fusion_power said:


> IMO, it would be counterproductive to focus entirely on one trait such as VSH when other traits such as mite entombment are available and effective. We should be working on bees that combine as many resistance traits as possible, caveat that some may be mutually exclusive.


Do you know what is the mechanism(s) that your resistance/tolerance to varroa feral swarms use in USA? Do you know if some research has been done on this aspect?


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## Eduardo Gomes (Nov 10, 2014)

Fusion_power said:


> IMO, it would be counterproductive to focus entirely on one trait such as VSH when other traits such as mite entombment are available and effective. We should be working on bees that combine as many resistance traits as possible, caveat that some may be mutually exclusive.


Yes Fusion the data from this research show that the mechanisms of resistance / tolerance to varroa are other than the grooming or hygienic behaviour. The conclusion I draw is that the response of bees to the challenge of the plague of mites can be and is very plastic . Here too the maximum that " beekeeping is local " seems to apply.

"_Based on the results of this study, *neither hygienic behaviour nor grooming behaviour can be considered characteristics responsible for the mite tolerance observed in this surviving honey bee population in Sweden*. Therefore, selection for these traits was probably not as important as traits related to mite reproduction for their survival with Varroa mites. This is an important observation considering the attention mite-resistant breeding programmes put towards these behavioural traits (Büchler et al. 2010; Rinderer et al. 2010)._" pg. 539

"Our results clearly demonstrate a significant reduction in the reproductive success of Varroa mites (measured as the ability to produce at least one viable offspring) in a European population of A. mellifera colonies where no mite control was practiced for more than 10 years. The surviving colonies had on average almost twice the proportion of infertile mites, more than twice the proportion of dead progeny, significantly reduced fecundity and an overall reproductive success rate of less than 50% compared with over 75% in control colonies. Delayed egg- laying by the mother mites was proportionally the most frequent cause of reproductive failure with dead progeny as the second most common cause. *Reduced fecundity, along with the reduced ability to produce viable female offspring clearly, is important to explain the lower mite infestation rates in the surviving population.*"pg.538


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## Eduardo Gomes (Nov 10, 2014)

This other research carried out in feral swarms of Avignon, France, to 2000 Km of Gotland, Sweden, hereby presents data also very interesting, in my opinion. For those who want to deepen the analysis and reflection on this subject I leave the site where they can consult the paper. The discussion of researchers around the phenomenon of coevolution deserved a lot of attention from me.

"_Honey bee societies (Apis mellifera), the ectoparasitic mite Varroa destructor, and honey bee viruses that are vectored by the mite, form a complex system of host–parasite interactions. Coevolution by natural selection in this system has been hindered for European honey bee hosts since apicultural practices remove the mite and consequently the selective pressures required for such a process. An increasing mite population means increasing transmission opportunities for viruses that can quickly develop into severe infections, killing a bee colony. Remarkably, a few subpopulations in Europe have survived mite infestation for extended periods of over 10 years without management by beekeepers and offer the possibility to study their natural host–parasite coevolution. *Our study shows that two of these “natural” honey bee populations, in Avignon, France and Gotland, Sweden, have in fact evolved resistant traits that reduce the fitness of the mite (measured as the reproductive success), thereby reducing the parasitic load within the colony to evade the development of overt viral infections. Mite reproductive success was reduced by about 30% in both populations. Detailed examinations of mite reproductive parameters suggest these geographically and genetically distinct populations favor different mechanisms of resistance, even though they have experienced similar selection pressures of mite infestation. Compared to unrelated control colonies in the same location, mites in the Avignon population had high levels of infertility while in Gotland there was a higher proportions of mites that delayed initiation of egg-laying. Possible explanations for the observed rapid coevolution are discussed.*_" in http://onlinelibrary.wiley.com/doi/10.1002/ece3.248/full


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## Snowhitsky (Mar 1, 2014)

mike bispham said:


> I think its broadly understood that traits are inherited, not taught.
> 
> 
> Mike (UK)


Mike, 

Yes that would seem to be the case according to this study: http://www.gmb.org.br/Revistas/V18/v18a028.pdf

However, I note on p178 that the II queens were introduced into mating nuclei containing brood, honey and pollen. Although they don't mention it, I suspect they must have added adult bees too and this seems to be implied a couple of paragraphs further on when they explain how they waited three months to be sure all adult bees were the II queen's offspring. I assume the added bees were from the same hive as the II queen and shared her traits.

I'd love to find out if the results would have been the same if the added bees had been from another hive with different but measurable VSH characteristics. That would clearly prove without a shadow of a doubt that VSH is a wholly inheritable trait and not a one transmissible between adult bees.

I know I'm grasping at straws but...

Thanks to Michael Bush for the list of articles, much appreciated.


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## Michael Bush (Aug 2, 2002)

>The latest data are from 2000. Are there more recent data and a follow-up?

Erickson retired shortly after that study. The model for the study was Dee Lusby. She is still not treating and keeping the number of hives she can keep up with (currently about 600 or so). At the time of the study her husband (now deceased) and her were keeping about 1,000.


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## Eduardo Gomes (Nov 10, 2014)

Thank you Michael Bush. Do you know if the average production of colonies of Dee Lusby is equal, higher or lower than average production of colonies in conventional manner in the region? As beekeeper who lives than the hives give me this aspect for me is very important. If you are comfortable to talk about your case will be better.


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## Eduardo Gomes (Nov 10, 2014)

For those who do not know it and are interested, in this short article of 2 pages the authors explain some questions and answer to some criticism to development programs of bees resistant/tolerant to varroa (see here please http://www.ars.usda.gov/SP2UserFile.../515-Danka--Comments on Varroa destructor.pdf.)


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## Michael Bush (Aug 2, 2002)

>Thank you Michael Bush. Do you know if the average production of colonies of Dee Lusby is equal, higher or lower than average production of colonies in conventional manner in the region?

I do not know her exact yield and I'm sure it varies greatly since she is in the desert. But she sells a lot of honey. Last I heard she had about 600 hives. She feeds no syrup and feeds back honey in a bad year. She has no other income except bees.


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## mike bispham (May 23, 2009)

Eduardo Gomes said:


> For those who do not know it and are interested, in this short article of 2 pages the authors explain some questions and answer to some criticism to development programs of bees resistant/tolerant to varroa (see here please http://www.ars.usda.gov/SP2UserFile.../515-Danka--Comments on Varroa destructor.pdf.)


Wonderful, thanks Eduardo! To add an opinion:

"We agree with Dietemann et al. (2012) that the effectiveness of IPM programmes (presumably including genetically resistant bees) for varroa control, depends on the dedication and proficiency of individual beekeepers. Our experience is that small-scale beekeepers are further ahead than large-scale beekeepers in acceptance of resistant bees. This is understandable, because commercial beekeepers are necessarily more averse to risks and the technology is new. However, the rate of adoption of agricultural technology tends to follow a logarithmic trend. Thus the adoption of resistant strains can be expected to accelerate, in part because of recent advances in basic IPM of varroa (e.g. improved sampling techniques for large-scale beekeeping; Lee et al., 2010) and in knowledge about the negative effects of acaricides on bees (e.g. Johnson et al., 2009)."

The broad understanding that treatments are now the sole cause of the problem they try to fix is becoming more widespread, and with that a general awareness that that's a daft situation. The myth that bees cannot adapt rapidly is being steadily worn away. The facts are starting to shine through. Thank God for the handful of conscientious and dedicated researchers.

Mike (UK)


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## squarepeg (Jul 9, 2010)

mike, i'm no expert but it seems that you are giving too much weight to the impact that treating for varroa has on the progress that the bees are making toward developing resistance. 

i'm not saying there is no impact especially in and around larger commercial settings. the distribution of the species however is widespread and the development of resistance carries on despite what we beekeepers do or don't do.

even in the treatment context, and given that treatments are not 100% effective, natural resistance is likely to develop albeit on a less accelerated timeline.

those willing to locate and propagate naturally adapted stock are having success off treatments, and the hope is that the traits will become understood and become more widely integrated into the metapopulation including commercial stock.

the real problem with treating is that treatments have been seen to become ineffective over time. this is a huge concern for those whose lives and livelihoods are invested in beekeeping. the commercials more than any of us have a vested interest in the promotion of resistant bees. calling for the widespread halt of treatments is just not realistic.


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## mike bispham (May 23, 2009)

squarepeg said:


> mike, i'm no expert but it seems that you are giving too much weight to the impact that treating for varroa has on the progress that the bees are making toward developing resistance.
> 
> i'm not saying there is no impact especially in and around larger commercial settings. the distribution of the species however is widespread and the development of resistance carries on despite what we beekeepers do or don't do.
> 
> ...


I think we'll have to agree to disagree on this one SP  In my understanding removing the pressure to adapt precisely does that. Again, in my understanding, in the specific case of varroa resistance I think its recognized that some of the governing genes are recessive, meaning a little interference goes a long way. 

Perhaps a lot of my passion about this is a local feature. I think that in most places in Europe beekeepers have, and are continuing, to suppress adaptation. We don't have the strong effort to move toward non-treatment that has been a feature of US beekeeping. I agree, it is happening in pockets. Then again I'm not well in touch with UK beekeeping, so perhaps I just don't know. 

Mike (UK)

Breeding for resistance to Varroa destructor in Europe*
Sélection d’abeilles résistantes à Varroa destructor en Europe
Auslese auf Widerstandsfähigkeit gegen Varroa destructor in Europe (2010)
Ralph Büchler1, Stefan Berg2 and Yves Le Conte3
http://www.apidologie.org/articles/apido/full_html/2010/03/m09147/m09147.html

Abstract
The rich variety of native honeybee subspecies and ecotypes in Europe offers a good genetic resource for selection towards Varroa resistance. There are some examples of mite resistance that have developed as a consequence of natural selection in wild and managed European populations. However, most colonies are influenced by selective breeding and are intensively managed, including the regular use of miticides. We describe all characters used in European breeding programs to test for Varroa resistance. Some of them (e.g., mite population growth, hygienic behavior) have been implemented in large-scale selection programs and significant selection effects have been achieved. Survival tests of pre-selected breeder colonies and drone selection under infestation pressure are new attempts to strengthen effects of natural selection within selective breeding programs. Some perspectives for future breeding activities are discussed.

7. PERSPECTIVES
⦁	Accustomed management techniques have to be revised. *Regular and uniform treatments of bee populations with highly effective acaricides are in opposition to field selection for resistance. *(MB's emphasis) To support the spread of more resistant stock, beekeepers need to identify (through monitoring infestation level) and exclude highly susceptible colonies from further propagation. As soon as the individual infestation of a colony exceeds certain threshold levels colonies should either be destroyed, or treated and requeened to prevent domino effects. Preference of shorter brood rearing periods, acceptance of temporary breaks in brood rearing and complete brood removal once a season are some tools beekeepers can use to lower the population growth of Varroa and thus to reduce their dependence on the use of miticide treatments which mask the advantages of mite resistant stock.


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## jim lyon (Feb 19, 2006)

squarepeg said:


> mike, i'm no expert but it seems that you are giving too much weight to the impact that treating for varroa has on the progress that the bees are making toward developing resistance.
> 
> i'm not saying there is no impact especially in and around larger commercial settings. the distribution of the species however is widespread and the development of resistance carries on despite what we beekeepers do or don't do.
> 
> ...


Well said SP. We are always concerned about resistance but from my perspective as commercials learn new management techniques the big picture is that things are getting better not worse. Sure, I treat, but I also incorporate TF stock into our operation and put a lot of effort into our selection process. We have our ups and downs as do all beekeepers but our ability to deal with varroa is infinitely better than when we were first impacted over 20 years ago. One shouldn't forget that since the impact of varroa a new market has developed for nearly 2 million strong hives in California in late winter and, whether it's fair or not, the ability of our industry to satisfy that demand has now become the new yardstick for bee health. For me, restocking our losses for a northern honeyflow is laughably easy compared to trying to get a high percentage of our hives strong enough to make grade in California. 
OK, I'm off the soapbox and back to work.


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## mike bispham (May 23, 2009)

Why doesn't that reassure me Jim! 



jim lyon said:


> We are always concerned about resistance but...


... other things matter more...



jim lyon said:


> ... from my perspective as commercials learn new management techniques the big picture is that things are getting better not worse.


Your perspective being you are better able to control varroa with a mix of treatments and management techniques that allows you to carry on not having to worry about whether your bees are developing resistance or not?



jim lyon said:


> Sure, I treat, but I also incorporate TF stock into our operation and put a lot of effort into our selection process.


Well, ok, this is the cruncher: do you mean selection for resistance? If so, how much effort? How do you judge its success? What progress are you making?

And then: what does that 'we' cover/ Is it your own operation? Is it all commercial operations?



jim lyon said:


> We have our ups and downs as do all beekeepers but our ability to deal with varroa is infinitely better than when we were first impacted over 20 years ago.


But is that simply because you've got better at managing varroa-vulnerable bees that are dependent on you? If so, how is that meant to impress the tf forum? 



jim lyon said:


> One shouldn't forget that since the impact of varroa a new market has developed for nearly 2 million strong hives in California in late winter and, whether it's fair or not, the ability of our industry to satisfy that demand has now become the new yardstick for bee health.


Quite. The yardstick is: can we operate competitively to meet this 'imperative' the holy 'market demand'. The trouble is that if you think like that there's no limit to the damage you can do. 



jim lyon said:


> For me, restocking our losses for a northern honeyflow is laughably easy compared to trying to get a high percentage of our hives strong enough to make grade in California.


I'm not sure what your point is here. But, sorry Jim, these sound to me like the same arguments made by fishermen as they dredge the last bits of life from the bottom of the ocean. 'Its ok we can do fish farming'. 

Maybe I have you wrong. Maybe you are concerned not to participate in the treatment cul-de-sac, and are making concrete steps to raise resistance?

Mike (UK)


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