Honey Bee Suite » varroa mites

Of feral colonies and varroa mites

Rusty — Fri, 13 Apr 2012 16:28:02 +0000

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

You are absolutely right that honey bees are not native to North America. But from the time they were brought over 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 and I believe at least some of these stories. So I tend to side with the 2% group.

One of you wrote that it wouldn’t be necessary for bees to swarm to transmit diseases to the wild stock because it 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 not 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.

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.)

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.

Rusty
HoneyBeeSuite

Feral colony in a bee tree. Flickr photo by Just Chaos.

Hopping mad at HopGuard

Rusty — Thu, 09 Feb 2012 15:23:15 +0000

I put off writing this post for a very long time—since November, actually. Although I often display irritation in my posts, I try damn hard to remain civil. But the makers of HopGuard have pushed my civility to the limit. I had to cool down for months before I could write something that wouldn’t get me banned from the Internet.

From the top, the story goes like this:

I do not use hard chemicals in my hives but, since mites are a problem, I use one of the so-called “soft” or “natural” products. Although I’ve tried formic acid-based products, I prefer the thymol-based ones, either Apiguard or Api-Life Var. I used them according to package directions and had excellent results. As far as I know, I never lost a hive to mites in the many years I used those products.

Like all treatments, however, they should be rotated with other treatments to lessen the chances of building resistant strains. When HopGuard came on the market I was ecstatic: here was a product that was easy to use, had an active ingredient other than thymol, and didn’t require the dreaded “fumigation chamber” in hot weather. I read everything I could find about it and wrote extensively about it here at HoneyBeeSuite.

When it came time to treat for mites last summer, I read the directions carefully and watched HopGuard’s own video several times. I calculated how many strips to use per hive based on the number of brood boxes and the number of frames covered with bees, and I staggered the strips in the pattern they recommended. I followed every last instruction from the package insert and the video to the letter.

I was happy with the way the bees reacted to the HopGuard and, although it was messy, I was happy with the ease of use. The insert said I could use the product up to three times per year, but I always treat for mites in August only, so I just crossed that chore off my list. Job done.

Everything was fine until, months later, I saw a post on BeeSource about “progressive” HopGuard treatments. Curious, I read the series of posts. The gist of the thread was that, since the HopGuard strips tended to dry out in the hive, they didn’t continue to kill mites after the first few days. As a result, beekeepers were adding a new set of strips every week for three weeks. According to the thread, Mann Lake, the company that sells HopGuard, was advocating this procedure.

I had trouble wrapping my mind around this. It sounded like an off-label use, something a reputable company would never advocate—at least not publicly. I re-read the label. It says that a treatment is one set of strips and that the treatment may be repeated up to three times a year. To me that meant maybe spring, summer, and fall . . . or something similar. No rational person reading the instructions would conclude it meant three weeks in a row.

I didn’t believe it, so I wrote to John I Haas, the parent company of BetaTec Hop Products. I received an answer that reads in part, “. . . the HopGuard strip does dry out over time in the hive which reduces its efficacy. In using only one round of strips when there is brood in the hive, the mite phoretic load will be reduced and this could help the beekeeper keep his hives healthy enough to get them to a time later in the year when other treatments and/or HopGuard can be used more effectively. . . . Tests by the USDA and by a number of commercial beekeepers have found the [sic] several consecutive applications do in fact reduce the overall mite load and have saved hives that would probably have died. The label does allow for multiple applications . . . up to 3 times per year. . . .”

But again, I ask you, how was I supposed to know that “up to three times a year” meant “three weeks in a row?”

By the time this little gem of wisdom came to my attention, I had already lost many of my hives. I’ve lost more since then . . . and all the post mortems indicate mites. After successfully wintering year after year by using Api-Life Var according to package instructions, I’ve now lost most of my hives by using HopGuard because I didn’t know that “up to three times per year” means “three weeks in a row.” You have no idea how hopping mad I am.

Furthermore, many of the good things I said about HopGuard in previous posts aren’t really true. For example, it’s not more convenient than other products if you have to apply it three times instead of just once, and it certainly isn’t cheaper. But more than anything, it seems unconscionable that a company would go to market with—and write instructions for—a product that they themselves didn’t know was going to dry up in three days. Didn’t anyone do field trials?

The makers of HopGuard cost me a bundle of money. Worse, I was an enthusiastic advocate of HopGuard. I promoted it, recommended it, and my posts about HopGuard have received much traffic. The boondoggle caused me to let my readers down. How many of them lost hives due to lousy instructions?

So that’s my story. I will rebuild my apiary, although not all at once. I’ve learned my lesson about trying new products. I apologize to any of my readers who lost their bees. To be fair, HopGuard appears to be an effective product, but the obfuscatory language is just plain unacceptable. So to BetaTec I say re-write your materials. Fix your website. Say what you mean. Get real.

Rusty
HoneyBeeSuite

Screen shot from Betatechopproducts.com, captured 2-8-2012.

Monitoring mites with a sticky board

Rusty — Thu, 26 Jan 2012 16:49:44 +0000

A lot is written about how to monitor mite loads with a sticky board. A sticky board is just a piece of thin wood or corrugated plastic that is covered with a sticky substance—usually pan spray—and placed below a screened bottom board. A certain number of mites drop off and stick to the board. The board is usually left in place for one to three days and then the mites are counted so that a “24-hour mite drop” can be calculated.

Some beekeepers use this magic number to decide if and when to treat for mites, but ideas differ about what this number should be. As an example, the Brushy Mountain Bee Farm site suggests treating for mites if your 24-hour sticky board count is greater than 5-10 mites in the spring or 50-60 mites in the fall. Some sources use just one number. The Virginia Cooperative Extension site reads, “If more than 40 mites are recovered [in a 24-hour period], then the colony should be treated.”

I have serious doubts about the validity of these numbers. The most obvious problem is that they do not take the hive population into account. A mite count of 40 in a single-deep, five-frame colony is very different than a count of 40 in a triple-deep, 24-frame colony. Mites per bee is the important number, not mites per bee hive.

Mite drop in the fall is greater than mite drop in the spring because, in the spring, most mites are under the capped cells where they are not going to fall off. Brushy Mountain recognized this in their estimate, but Virginia Cooperative Extension ignores it. Neither site discusses differences in mite count seen in various subspecies of honey bee, or differences in counts due to local climate or latitude.

The way I see it, the best we can hope for from a sticky board is to give us an idea of increase or decrease in mite loads. Or, if a beekeeper is diligent about estimating colony strength, he can assess mite drop as a function of colony strength and from there, decide when to treat.

Like many issues in beekeeping, determining when to treat for mites is a skill learned by trial and error. It is nearly impossible to make “rules” that can be used successfully, although people keep trying. All beekeeping is local and all beekeepers are different. The main problem with teaching rules instead of concepts is that it gives new beekeepers false hope, and when they do everything the books say, and their bees die anyway, they wonder if it’s worth it.

So what do I do? No sticky boards. For the past six years I’ve treated for mites once a year with one of the thymol-based products. I do this in August when brood is low and while there’s still time to raise a crop of winter bees that haven’t been exposed to the thymol. I’ve had no problems with mites or mite-borne diseases until this year when I switched to HopGuard—but that’s an entirely separate subject. More on that later.

Rusty
HoneyBeeSuite

Faster than the speed of mite

Rusty — Tue, 22 Nov 2011 18:23:05 +0000

Let’s say you have a brand new colony of bees that is guaranteed to be uninfected by Varroa mites. How does your colony become infected and how fast do the mites reproduce? Let’s take it from the top:

One fine spring day one of your bees shares a flower with an infected bee from another colony. Busy doing what bees do, they rub against each other as they seek nectar or pollen and, bingo, a phoretic mite (a mite taking a ride) passes from the foreign bee to your bee.
Your bee flies home with her load of goods: two full pollen sacks and a gravid (pregnant) female Varroa mite. You are toast.
Once in the hive, the mite jumps off her ride and cases the joint. She breathes in luscious smells—larvae in their fifth day of development, just ready to be capped. She especially likes the smell of those drone babes, but there are so many cranky bees around, she decides to crawl into a worker cell before the bees have a chance to cart her away.
She scuttles down to the bottom of the cell and submerges herself in brood food with only her breathing tube breaking the surface. She hunkers down and waits, a mite at the end of the tunnel. Patience, she knows, is a virtue.
Eventually the immature bee consumes the brood food and the female mite crawls free.
Meanwhile, the honey bee larva has transformed into a pupa and the mite pierces her soft young body and feeds, vampire-like, on the bee’s hemolymph (blood). Yum. Slurp, slurp.
The mite feeds for about 60 hours, building her strength for the business of egg-laying. The first egg she lays is haploid, meaning it has only half of a full complement of chromosomes. This grows into a small but mighty male mite.
Then, once every 30 hours, she lays another egg. All of these subsequent eggs are diploid, meaning they have a full set of chromosomes and are female.
All the mites go through a series of stages: larva, protonymph, deutonymph, adult. As adults, they mate while still within the capped cell. After the male mite mates with his sisters, he dies. Good riddance, but the damage is already done.
The female mites continue to live off the female worker bee until she emerges from her cell. These mites are then carried about the hive where they smell those piquant five-day-old larvae. When they get to feeling frisky, they jump off their steed, crawl under a larva, and prepare to start a family of their own.
But now, instead of one gravid female mite, you have 2.2 gravid females. (Okay, from a practical point of view, it’s just two. But the 0.2 becomes statistically significant as the population builds. Simply put, every fifth cell yields 3 gravid mites.)

The time spent in the larval stage varies bee-by-bee, which is why some cells produce more mites than others. And the drone larval stage is naturally longer, so each drone cell can produce more mites than a worker cell. Nevertheless, the actual number of reproductive mites produced per cell is smaller than the theoretical number because not all eggs are viable and not all mites are able to reproduce. Thank heavens there is something on our side.

Still, the increase in mite populations is staggering, and it doesn’t take long for a colony to become overwhelmed. And anything that increases the time honey bees spend in the larval stage—such as some pesticides—can dramatically and quickly increase the Varroa mite load.

Rusty

HoneyBeeSuite.com

Adult varroa mite on honey bee larva. Wikimedia Commons photo.

Small cells do not control Varroa mites

Rusty — Thu, 17 Nov 2011 19:34:09 +0000

Whenever I write about small-cell combs and Varroa mite control I incur the wrath of the believers. It’s the one subject that delivers something very close to hate mail. So with that in mind, I will say it again: small-cell combs will not control your Varroa mites.

In a 2011 paper by Thomas D. Seeley and Sean R. Griffin[1]—both of the Cornell University Department of Neurobiology and Behavior—small-cell combs were once again found to produce no fewer mites than regular-sized combs. This work, along with similar experiments reported by Ellis et al. 2009, Berry et al. 2010, and Coffey et al. 2010, demonstrates that small-cell combs given to European honey bees do not significantly reduce either mite loads or mite drops compared to hives with similar genetics and similar mite infestations.

In their experiment, Seeley and Griffin studied seven pairs of colonies. Each pair was started from a strong colony with a high mite drop. In order to assure that each pair had similar genetics and similar mite loads, the bees were shook from the parent colony and then divided into two packages. Each package was then given a new Minnesota Hygienic queen and fed sugar syrup. After three days, one package from each colony was put in a hive with standard-size combs (5.38 mm) and the other package was put in a hive with small-cell combs (4.82 mm).

Once a month for five months, the seven pairs of colonies were measured for colony strength, mite infestation, and worker size. The paper contains many interesting tidbits but, to make a long story short, by the end of the experiment Seeley and Griffin found no significant difference in either infestation rates (mites per 100 worker bees) or mite drops. They also found very little difference in worker size. Even though the small cells were 10.4% narrower than the average standard cells, the worker bees showed only a 2.1% decrease in head width and a 3.5% decrease in thorax width.

Taking this a step further, they divided the average thorax width of workers in standard cells (3.95 mm) by the cell width (5.38 mm) to get a “fill factor”– or the percentage of cell filled with bee (73%). Similarly, dividing the average thorax width of a small-cell bee (3.81 mm) by the small-cell width (4.82 mm) yielded a fill factor of 79%. This throws doubt on the commonly held belief that there is not enough room inside a small cell for mites to reproduce effectively. Neither 73% nor 79% are very tight fits, so there is plenty of room to grow many mites in either case.

I hear plenty of conflicting stories—anecdotal evidence of how changing to small cells cured the mite problem. But when researcher after researcher cannot reproduce those results, I have to wonder if the anecdotal cases aren’t due to exogenous variables or just plain luck. Sometimes we want something so badly we can’t think beyond the wishing. Believe me, if I thought there was a breath of truth to small-cell mite control, I would switch tomorrow.

Rusty

HoneyBeeSuite.com

[1] Seeley, Thomas D. and Griffin, Sean R. 2011. Small-cell comb does not control Varroa mites in colonies of honeybees of European origin. Apidologie 42:526-532, DOI: 10.1007/s13592-011-0054-4.

HopGuard: first impressions

Rusty — Tue, 30 Aug 2011 16:36:16 +0000

It’s been over a year since I last treated for mites. However, due to a recent increase in deformed wing virus, I decided to treat for mites before winter sets in. I prefer winter bees (those that live many months cooped up in the hive) that have not been directly exposed to any mite treatment. Consequently, I strive to have mite treatments completed by the end of August.

Although the directions say that honey supers do not have to be removed during treatment, I received a note from a reader saying that he could detect the odor of HopGuard in his honey supers. I decided it wasn’t worth the risk, so I pulled the supers before doing the treatment.

As a point of comparison, the only mite treatments I have used in the past have been ApiLife Var (a biscuit-like thymol product), ApiGuard (a gelatinous thymol product), and Mite-Away II (pads soaked with formic acid). Like HopGuard, these products are considered “soft” chemicals, meaning they are naturally-occurring substances that kill mites rather than synthetically manufactured molecules.

I found the previous products to be extremely effective but really unpleasant. The worst part is having to make the hive into a “fumigation chamber” and locking down all the natural ventilation. Also, I hated the smell of those products, so I was ready to give HopGuard a try. So here are my reactions, divided into positive and negative.

Positive:

I was pleasantly surprised by the odor. I was expecting the worst after that one reader comment, but I found very little in the way of offensive odor, even when opening the new package. To me it smelled faintly of hops—not strong like when I’m brewing beer—but just slightly hoppy.

Quantities were easy to figure for each hive. One strip per five frames of bees seemed a little more tailored than the quantities recommended by the other products. I used anywhere from one to six strips, depending on the colony size.

The bees seemed unperturbed when I placed the strips in the hive. My bees usually go ballistic when I apply the other products, but they seemed not to be offended by the odor of HopGuard any more than I was.

In the past when I had to lock down the ventilation, mite treatments were followed by much bearding and general unrest. With the HopGuard everything seemed normal after the application.

HopGuard lists no temperature restrictions the way the other products do. The thymol products are ineffective when it’s too cold, formic products are dangerous when it’s too hot. HopGuard is just plain easier.

The price: this stuff is a whole lot cheaper than other soft treatments. It is actually affordable.

Negative:

OMG! HopGuard gives new meaning to the word “messy.” I was ready for this, having watched the video, and even brought rags and extra nitrile gloves with me. Still, after the first three or four hives, HopGuard was everywhere. By the time I was done, I had to wash my hive tools, the smoker, the propane torch (used for lighting the smoker), the bucket I used to carry things, my bee suit, rags . . . even my shoes. Beekeepers are used to things sticky, but even so . . .

The directions for use are glued to the outside of the foil package. They became completely saturated and unreadable after a few hives. I would prefer to have the directions separate from the package. Although some general directions are found online along with the video, I haven’t found the actual package insert. It would be a nice thing to have.

I don’t like the idea that I need to distribute the strips among the brood boxes. For the most part, I can’t move my brood boxes this time of year. Some weigh 80 or 90 pounds, and I weigh like 115, so moving them just ain’t gonna happen. I ended up carrying an extra brood box with me, removing enough frames from the top box so I could reach down into the lower box and insert the strips. Then I had to replace the frames in the top box and add those strips. Meanwhile HopGuard is smeared over every conceivable surface and it’s about 200 degrees in my bee suit. This problem was even worse in my triple deep hives.

Related to the above is the fact that I don’t like to tear my hives apart this time of year. Honey cells inevitably break open and attract robbers and predators. In addition, I run the risk of killing the queen in a season when the drones are gone and the colony can’t replace her. Is it really necessary to put the strips in each brood box or could they all be put in the top box?

When I opened the foil package, I knew I would not use the entire package in one day. In light of that, I opened the package as carefully as possible, conserving ever millimeter of the bag length. Still, at the end of the day, there was not enough bag left to wrap and store the contents. The directions say you can store the extra strips in the foil bag, but there’s no way. I folded the foil over as well as I could, then wrapped the foil bag in plastic wrap, and put the whole thing in a plastic bag, and put the bag in a bucket. Next time I went to use it, HopGuard had leaked everywhere. I hope BetaTec is reading this because we need a longer bag!

If the HopGuard works, I would use it again in spite of the inconvenience. I liked the way the bees responded to it, I like the price, I like the smell, and I like the fact it is made from all food-grade products. These are all big advantages. Still, if some of the other issues were addressed I think the product would be a lot easier to use.

Rusty

HoneyBeeSuite.com

Can powdered sugar control Varroa mites?

Rusty — Sat, 20 Aug 2011 16:35:48 +0000

This is a question I’d rather sidestep, but it keeps insinuating itself into my inbox. So I’ve finally decided to take a quick stab at this complex (and oftentimes heated) debate.

The theory behind powdered sugar dusting it that the bees will groom the sugar off themselves and the hapless mites will drop from the bees and fall through the screened bottom board and out of the hive. Mites on the ground soon become food for something else. Good riddance. Any inert powder applied to the bees will have a similar effect, but powdered sugar is a good choice because it is readily available, inexpensive, and harmless to the bees.

Most sources I consulted recommend one cup of powdered sugar per brood box. However, those who use bellows-type applicators use less. Those who use powdered sugar dropped through a food strainer use considerably more. As I said, the sugar is harmless to the bees, and even the small amount of corn starch found in commercial powdered sugar has no ill effects.

Powdered sugar also has no harmful effect on mites. Some folks think the sugar makes it harder for the mites to hold onto the bee, others say it makes no difference. Most think it is just the act of grooming that dislodges the mites. Consequently, most mite drop after a powdered sugar application occurs within the first few hours and decreases quickly after that.

So far, I’ve given you all the good news. Now, the rest:

Powdered sugar only affects phoretic mites—those mites that are riding around on the bodies of honey bees. By far the most mites, especially during spring and summer, are inside the cells of capped brood. These mites are oblivious to blizzards of powdered sugar.

That means that powdered sugar must be applied regularly to the hive in order to remove mites as they hatch along with brood. In his experiments, Randy Oliver found that the more treatments you applied, the more mites you “killed” (dropped out of the hive). Treatments every week killed more mites than treatments every two weeks, which killed more mites than treatments every month. Oliver found that the only treatment schedule that effectively suppressed mites over long periods was once per week.

Another factor is the method of application. Some experiments have shown the best coverage is achieved by removing every frame from the hive, treating both sides, and then replacing the frame. This is an egregious amount of work and a huge disruption of the colony, especially if done on a once-per-week schedule. In fact, except for hobbyists with just a few colonies, it would be virtually impossible. Other experiments have shown that dusting the top bars is more effective, as long as at least some of the sugar immediately falls through to the bottom of the hive.

Another issue is humidity. Powdered sugar is amazingly hydroscopic, meaning it has an attraction for water. If you keep bees in a humid climate, or if your hives are full of moisture, the sugar will clump on the bees instead of dusting them, a situation that reduces the efficacy of the treatment.

In spite of the negatives, sugar dusting has been found to significantly reduce adult mite populations at times when little brood is present. Colonies in a summer nectar dearth or loosely clustered winter bees may be effectively treated with powdered sugar. Also packaged bees, swarms, and shook swarms—units without brood—may benefit from the treatment as well.

My own opinion is that powdered sugar dusting is effective only when used in combination with other Varroa management protocols such as drone trapping, queen removal, splitting, and the use of organic acids. Except under the most onerous treatment regimens, powdered sugar dusting by itself is probably insufficient for long-term Varroa management.

Rusty

A bit more about VSH

Rusty — Thu, 09 Jun 2011 16:00:12 +0000

A reader asked how the VSH bees detect mites within the cell. So far, I cannot find a detailed explanation. Many scientific papers discuss various aspects of mite removal and efficiency, but the ones I read didn’t answer this specific question.

Varroa sensitive hygiene was originally discovered by the USDA Honey Bee Breeding, Genetics and Physiology Laboratory in Baton Rouge, LA. After discovery of the trait in nature, they bred lines of bees with amplified hygienic behavior. According to the USDA, VSH bees only remove pupae infected with mites that have begun to reproduce; they do not remove pupae with mites that are not reproducing or that are sterile.

The USDA online literature says the bees “sniff out” reproductive mites but it doesn’t say more than that. According to Glenn Apiaries, a company that sells VSH breeder queens, VSH bees also show activity against tracheal mites, American foulbrood, chalkbrood, wax moths, and small hive beetles.

Based on that information it sounds as if the VSH bees are recognizing all sorts of wildlife that doesn’t belong in the hive. Odor is the most likely mechanism, but so far I haven’t found a specific citation.

Rusty

Wednesday wordphile: hygienic behavioral disorder

Rusty — Wed, 08 Jun 2011 19:50:44 +0000

Let’s back up for a moment and first define Varroa sensitive hygiene or VSH. VSH is a trait found in some honey bees that causes them to remove Varroa-infected pupae from the brood nest. A number of breeders around the country have developed lines of honey bees with enhanced VSH. When these bees detect the presence of Varroa mites beneath the cell cap, they rip the cap off and haul the pupa out the front door. Videos of this process are amazing in a lurid sort of way.

For many years the VSH trait has been seen as the potential savior of honey bee populations. However, a number of beekeepers are now reporting colonies of VSH bees that have gone out of control, ripping out not only the infected pupae but all the pupae. While this certainly takes care of the mite population, it also takes care of the bee population. Oops. This trait is sometimes called hygienic behavioral disorder.

So what causes it? Researchers are not exactly sure. Perhaps all the brood in those hives were infected. Or perhaps the bees become so sensitive to Varroa that even the brood near to infected brood is hauled away.

It seems likely, though, that there is a distribution of Varroa sensitivity in the VSH lines. In other words, some bees will be extremely sensitive, some moderately sensitive, and some barely sensitive. So occasionally you will get a queen who has the extremely sensitive gene which she passes on to her daughters. These bees, in turn, rip out all the brood.

This trait should be somewhat self-limiting. If the queen can’t produce new queens because they all get ejected from the hive, the trait would eventually disappear.

Another complaint I’ve heard from some beekeepers is that VSH bees are poor honey producers. However, most beekeepers say there is no difference in honey production between VSH bees and other bees. It would be interesting to know whether those beekeepers reporting poor honey production have the extremely hygienic type. If so, it may be that low brood survival is causing low honey production in some VSH hives.

Wednesday wordphile: survivor stock

Rusty — Wed, 25 May 2011 17:52:31 +0000

Recently, during a discussion with a professor of entomology who is also a beekeeper, I used the term “survivor stock.” He looked at me as if I’d just left my ship hovering above a corn field, slid down the chute, and landed on three feet.

It reminded me of why I write Wednesday Wordphile in the first place: because a word or term that is obvious to one person may be completely foreign to another. Nothing jeopardizes communication faster.

Okay, so survivor stock can be any organism that survives a stressful event and lives to tell about it. The “event” can be anything that a scientist wants to study. With honey bees, the event may be winter. Or it may be a predator, pathogen, parasite, or poison. The survivors of the event are then used to breed more bees in the hope that the genetics that allowed survival will be passed on to the next generation.

Sometimes this works and sometimes it doesn’t. Some other random or unknown cause may have allowed certain individuals to survive, and this external (or exogenous) variable may have nothing to do with the bees’ genetics. But you don’t know that in the beginning, so you experiment. You raise bees from the survivors and see if those bees can survive similar conditions.

Today the term is most often associated with Varroa mites. The survivor stock is comprised of bees that successfully overwintered in the presence of Varroa mites with no chemical treatments. If the offspring of these bees is also able to survive in the presence of mites, breeders will be on their way to producing a Varroa-resistant strain.