varroa mites

Feral colonies and the quick spread of varroa mites

Feral colonies fall to varroa mites just as easily as managed colonies.

Feral colonies were killed by varroa mites as they spread across the continent. Today, few of the very old wild colonies still exist.

I received many well-reasoned responses to yesterday’s post about the spread of varroa mites. Rather than attempting to answer them separately, I decided to write a follow-up.

Honey bees have naturalized in North America

You are absolutely right that honey bees are not native to North America. But from the time they were imported by the colonists in the early 1600s, until the introduction of the varroa mite in 1986, honey bees naturalized across the continent. They thrived and could be found nearly everywhere. But all that ended when the varroa mite entered the feral stock and, for all practical purposes, wiped it out.

Some estimates in the scientific literature put the remaining feral stock at about 2% of pre-varroa levels. Other accounts say the number is zero, and any seemingly feral colonies simply escaped from managed hives within the last two years and will not survive.

I’m not an expert on this issue, but I’ve heard many accounts of hives that have persisted for more than a decade and are still going strong. I believe at least some of these stories, so I tend to side with the 2% group.

Drifting bees transmit mites as easily as swarms

One of you wrote that it wouldn’t be necessary for bees to swarm to transmit diseases to the wild stock. You point out that the spread would happen naturally as populations of bees mix together. That is also true. In my post yesterday, I was not suggesting we could protect wild populations by keeping our bees from swarming. Not, at all. My objection was to the idea that we are somehow helping populations of “all bees” by letting our swarms go.

I don’t believe swarms on the loose are going to help or hurt feral colonies—not at this late date. But there are many reasons to manage your swarms, especially if you are an urban beekeeper.

Besides, if “helping the bees” were that simple, we could all let our swarms go this summer and the whole bee crisis would be over in one season.

Survivor stock may fail under different environmental conditions

Several of you wrote that if we let managed swarms escape, the principle of “survival of the fittest” would take over and before long these colonies would morph into varroa-resistant, disease-resistant stock. That would be great. That is what we all want. But so far, it hasn’t happened. Many of the feral colonies that have been used as “survivor stock” have not persisted under managed conditions—a situation that suggests environmental factors, rather than genetic ones, kept them alive in the wild.

The honey bee genome is a flaky thing. Whereas almost all insects evolve tremendously fast—think mosquitoes and cockroaches—honey bees do not. They do not have the wide array of genes for detoxification and disease resistance that other organisms have. A creature cannot evolve if the genes don’t exist, and this seems to be particularly troublesome in honey bees.

The theory is that these genes, if they ever existed, were lost as the honey bee became a communal animal. In honey bees, disease resistance is a colony function where individuals sacrifice themselves if they become ill, and where cleanliness—including the removal of parasites, dead bodies, sick bees, imperfect bees, pathogens, mold, and mildew—is practiced relentlessly.

Like wearing a breathing mask when the flu arrives, these are mechanical rather than immune responses to disease. (Although the mechanical behaviors are themselves genetically transmitted, there is a distinct difference in the mechanisms.)

So far, we have found no reliable genetic answer to varroa in America

Breeders who are trying to raise varroa-resistant stock are concentrating on these hygienic behaviors, rather than simple genetic resistance, which is so rare in honey bees. Although there has been some notable success in producing varroa-resistant strains, the resistance essentially disappears when these special bees are bred back into the general population.

Now, 26 years after the introduction of varroa, we still don’t have a viable solution to the problem. It would take an extraordinary genetic mutation to suddenly provide resistance to varroa—or at least to the viruses it carries. Extreme mutations are rare in any species, but in a social organism where only a few individuals pass on their genes (the queen and a few drones), it is even less likely to happen.

Honey Bee Suite

Feral colonies die of varroa mi
Feral colony in a bee tree. Flickr photo by Just Chaos.


  • Rusty

    Thanks for the updated article. I didn’t mean to start a controversy with my comment on your previous article. I appreciate everything that I learn from your site, along with the general entertainment value as well. One thing I have learned over the past year is that if you want 25 different beekeeping opinions, you only need to ask 25 beekeepers!

    Have a great day and thanks for your website.

    • Brian,

      No problem. Based on all the comments, I think I didn’t make my meaning clear the first time around.

      Btw, the conventional wisdom is that if you want 25 different opinions, you need to ask only 10 different beekeepers. It’s that bad.

  • Hi,
    The two recent articles and the discussion left me wondering–have breeders ever concentrated on selecting for bees that do not show hygienic behaviors as a way to get some of the simple genetic resistance that other insects have? Maybe if some breeders went this direction while the others went the hygienic direction you could eventualy hybridize the two. Generally, I tend to believe that any breeding program that concentrates on one (or a few) specific traits (even if it is a helpful trait like good hygiene) is not helpful… but if different breeding programs went in multiple directions instead of only the hygienic direction maybe that could be helpful?

    • That’s an interesting question and I don’t know the answer. I know that breeders through the years have selected for various different traits such as gentleness, honey production, and overwintering ability with various degrees of success. But whether selection against hygienic behaviors has ever been tried, I don’t know. You’re thinking that if they weren’t hygienic, immunity genes rather than behavior genes would have to see them through, and as such, it might force the immunity genes to develop and evolve. Definitely a creative idea. I agree that selecting for one trait and one trait only, can lead to very negative results.

  • I have been experimenting with placing several hives on top of a “debris box” This is a deep box with solid bottom filled with rotten wood and similar wood debris. I have had these in service for about six months now. First observation was the smell. Much like all the feral hives I have removed through the years was there now in my hive. I treated one with mite-away. First time for that. To my surprise. Several weeks later was the bottom had no dead bees inside. Even down in the bottom of the debris. First time this spring. Still smells great. Wood litter in bottom seems to be now covered in propolis. Still very clean. This hive has insulated bodies which I’m now using all year here in southern Virginia. I’m trying to more closely replicate natural hive conditions.

    • Jay,

      Interesting concept. Have you had any problem with small hive beetles? Since they tend to pupate in the soil close to beehives, I was wondering if the debris box would turn into a nursery. If shb are not a problem it seems like the debris box would act like a compost heap and generate heat for the hive.

  • I am waiting to see if it becomes a problem with hive beetles. Hoping for a better natural environment within. It has seemed to stay warmer than my other hives. They seem ready to propolis the bottom area. They are making a propolis trap. Lol
    Time will tell.

    • Lorna,

      After ten years, I would say not much has changed. During that time, Tom Seeley wrote about his study of feral colonies in the Arnott Forest of northern New York State. Those feral colonies lived for many years, but when some were transferred out of the forest, they died of varroa. That is exactly what was predicted.

      We still don’t have any reliable genetic cures. Because of all the usual reasons, any in-bred traits quickly “wash out” of the population after the progeny of the inbred bees crosses with local stocks.

      It’s fascinating to me that I wrote about “herd immunity” (using different terminology). I speculated it wouldn’t work to control the varroa problem, and I still don’t believe it will. We’ve pretty much let the viral diseases rip across the continent and, in my opinion, honey bees are just getting harder and harder to keep–not easier.

      I mentioned “masks” too, which also surprises me. I’m so glad you asked about that post.

      Personally, I don’t think we will ever control the mites. I’m expecting future research to go toward trying to control the viral diseases instead. An mRNA fix, anyone?

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