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Stratiolaelaps scimitus for Varroa control

I have spent the last two days reading everything I could find about Stratiolaelaps scimitus as a control for Varroa destructor. And my conclusion? It won’t work.

Some beekeepers report success, but the experiments—at least those I’ve been able to find—have been small and anecdotal with no statistical analyses. I understand that some larger and more rigorous tests are underway, but until results come in, I remain skeptical due to the life cycle and biological preferences of the Stratiolaelaps mite.

If you are unfamiliar with this creature, Stratiolaelaps scimitus (formerly known as Hypoaspis miles), is a predatory, soil-dwelling mite that has been used for the past fifteen years as a biological control agent against fungus gnats, spider mites, poultry mites, poultry lice, and similar agricultural pests. It lives, eats, and reproduces in the surface layers of the soil and is native to North America.

Since this mite has an appetite for other mites, beekeepers have been experimenting with introducing it into beehives in the hope it will eat Varroa destructor. A vermiculite medium containing the mites is usually sprinkled on a sheet of paper on the top bars. Apparently the mites, looking for breeding grounds, pass down through the hive, snacking on Varroa trail mix as they go in search of moist soil. Each Stratiolaelaps mite can eat up to five prey items per day.

S. scimitus
Stratiolaelaps scimitus. Photo by Biological Services.com

Think of it this way: You and your friends live in New York City (the soil). One day you are scooped into a canister and dumped in Hartford, Connecticut (the hive) with no vehicle (wings). You decide the only way to get home is to walk (across the frames). So you head for home, stopping along the way to snack on hamburgers (Varroa). You and each of your friends eat five per day. Although this is a lot, there are an endless number stored in freezers (brood cells). Once you arrive in New York City (the soil) you have no incentive to go back to Hartford (the hive), you are tired of hamburgers (Varroa) and, in any case, the food is better at home (tender immature life forms).

Although Stratiolaelaps will eat Varroa destructor, they prefer eggs and immature arthropods rather than full-grown adult prey. And when they are “on the road,” traveling toward home, they can’t even get to the eggs or nymphs of the Varroa mite because those life stages are protected by sealed honey bee brood cells. Even when the home pantry is devoid of tender life stages, the Stratiolaelaps is perfectly happy with a diet of algae and plant debris, and will not go in search of Varroa burgers.

So, as a method of Varroa control, it lacks staying power. The Stratiolaelaps eat while they are passing through, but they don’t hang around, they don’t enter brood cells, and they can’t find patches of moist soil to breed in. All this means the Stratiolaelaps must be re-introduced multiple times per year just to lessen the number of phoretic Varroa mites.

Yes, I know there is a lot of excitement about them right now and they have a host of supporters, but when you look at the vital lifestyle issues, I don’t think the excitement is justified. It’s okay, you can call me Scrooge.

Rusty
HoneyBeeSuite

Comments

Nick
Reply

Happy New Year Scrooge! 🙂

Seriously, Rusty, I think you are right. This isn’t *the* Silver Bullet. Might it develop into another tool for control? Maybe, maybe no. If climate and temperatures were amenable, I could see an application during the low brood period of winter, similar to the timing for those that use oxalic. Who knows?

I do like the approach. ‘Even fleas have fleas.’ Whether it works out to be something that sees hives as a Drive-In for a varroa burger, or plays the part of the remora for the shark, I’m fine with some sort of DOFT friendly cohabitants.. or migrants.

I’m of two minds on your analogy. Well done, in the sense of Stratiolaelaps’ travel and eating preferences. As ever, your fingers do good things with a keyboard. However, I don’t know if I’ll look at a hamburger the same way, at least for a while. If I find myself taking ketchup and mustard out to the hives, I hope you’ll forgive me if I ‘mutter’..

Happy ‘little bit longer days’ and a Happy New Year to you and yours.

Nick
Kent, WA

harold meinster
Reply

I know we are grabbing at straws and I personally will try all combinations of techniques to rid the Varroa from my hives. I just lost my pride and joy hive to Varroa very early into the winter season due to varroa over taking my girls.

I feel the best defense is if the GOVT agencies involved develop a Varroa mite lure that brings them into a select honey bee cell and traps them. We than can rid them from the hive and stop the infestation.

Only an organization that has the tools and equipment can do this. We beekeepers alone do not have the resources.

Nick Holmes
Reply

Scrooge!!

🙂

Aren’t you missing out that if you are content to reapply several times a year it will work, by your own words? More importantly it will work without having to introduce chemicals into the hive?

I use nematodes to control slugs on our allotment, after 6 weeks I have to apply them again as the nematodes die back to background levels, but by then the plants have taken a hold and are not so susceptible to slug attack on baby leaves. I could use slug pellets, but I’d rather take the organic route where one is an option. Is that not working? Because t works as far as I am concerned.

In the early spring will not this stratiolaelaps knock down the varroa population and allow the colony to get established for a productive spring harvest, and with strong numbers give it a better fighting chance through the rest of the year?

Some say that a treatment will last several weeks, some say 3 months, although I plan to find out for myself this coming year. I know a lot of people who dust with icing sugar several times a year as a ‘keeping the numbers down’ solution, although I don’t. Is having to ‘rinse and repeat’ a definition of not working? I use api life var as a ‘soft’ more naturally occurring chemical presently, but I’d much rather not use something that the bees surely can’t ‘appreciate’ having to live with as they are so sensitive to smell.

For all that I have read of yours Rusty, I am surprised that you would so readily dismiss this solution, with all the advantages it has to offer; a key one being fewer chemicals in the hive. Skeptical is one thing; I’m skeptical which is why I’m ‘testing’ on only 2 hives rather than running out and ‘dusting the apiary head to foot’; but saying “it won’t work” in your opening line, seems rather final, with the only (admittedly potentially less rigorous) tests done suggesting it does work, and none, that I have seen, to the contrary.

Stretching the Scrooge metaphor, get out of the counting house and see what life has to offer. Try them for yourself, it might just turn out that you like them.

Nick

P.S. One thing I read suggested having a soil floor section in the hive for the stratiolealaps to live in. Lots of people like to pop out for a burger now and then, especially if someone keeps dropping them on your head to keep up your appetite for them, and given an otherwise empty plate might this not work? Maybe I stretched that scenario too far, but I won’t know unless someone tries it.

Rusty
Reply

Nick,

As a general rule, I’m all for biological control, and I actually did quite a bit of study on it as a post-grad. We have an excellent example here in western Washington, the cinnabar moth that is gobbling up tansy ragwort. So in principle, I think it is good; I just don’t think this particular organism is a good answer for this particular pest. As I said in the post, I don’t think their biology is compatible enough to be a good fit.

You keep repeating your warning about chemicals in the hive, but I don’t believe that by saying this organism won’t work that I’m advocating chemicals in the hive. I never said or implied that. I’d love to see a biological control be the answer to Varroa mites.

Also, there are factors involved which I didn’t go into, one being the expense. The little dudes are pretty expensive, especially when you consider overnight shipping, which would put a damper on the solution for many people. We need a solution that is both reliable and affordable, not something only available to affluent beekeepers.

Then, too, many of the small studies showed no change in the mite count after treatment, and those that showed some improvement found that the count rebounded almost immediately. Because of these variations, it is clear that a large and controlled study needs to be undertaken and I believe at least two such studies are underway.

I was asked for my opinion by another reader on this subject and that is what I wrote. I made it clear it is my opinion. What’s more, at this point, I’m sticking with my assessment that the two organisms have needs and lifestyles that aren’t what we are looking for, or at a cost we can absorb.

If you want to experiment with Stratiolaelaps, by all means, go for it. I would love to hear how it works for you.

nick holmes
Reply

So, I am so keen to try this because I don’t have a ‘good’ non chemical alternative. The cost doesn’t seem to be too bad here in the UK compared to chemical treatments about $6-7 per hive. Admittedly I would like to be paying less but I am willing to try for that much.

I appreciate that this is your opinion, I guess I have always agreed with your opinion previously and this time hope might be clouding my judgement.

All the best

Nick

Mark Martin
Reply

Maybe it would be more effective during a forced broodless period? Too bad those critters probably wouldn’t survive freezing temps though…

David
Reply

I cringe at the idea of introducing biological controls into a hive. Introduce a new mite to control the old mite. Introduce spiders to control the new mite. Bring in a frog to control the spiders. Bring in a bird to control the frogs. I forget… What was i keeping? Bees? It won’t go down like that in a beehive, of course, but bringing in a “good” pest to control a “bad” pest can come with serious unintended consequences. I wish beekeepers would focus on breeding better bees instead of searching for unsustainable magic bullets. After all, we are beekeepers.

Rusty
Reply

David,

Even though I love the idea of biological control, it can have scary and far-reaching consequences. Did you ever see “Cane Toads: An Unnatural History (1988)”? It’s a 45 minute documentary (and one of the weirdest films I’ve ever seen.) It’s on YouTube.

Rusty
Reply

Emily,

Yes. Another beekeeper sent me the link. Thanks so much.

M.S. Patterson
Reply

Seems like these guys could be great for helping to control parasitic mites in soil-dwelling/ground-nesting bees of various sorts, but they do indeed seem rather incompatible with honey bees.

Rusty
Reply

Interesting thought. I wonder if they would work on bumble bee mites?

M.S. Patterson
Reply

Might be worth investigating. I recall that B. impatiens is used for greenhouse pollination, but I’ve no idea what commercial nests of them are like, how they’re managed, etc, so I couldn’t guess whether or not they’d be more compatible with the predatory mite lifecycle.

There’s still the problem of S. scimitus not being able to get at any parasitic mites that might be inside a sealed cell. Do you think they’d be effective against tracheal mites?

Rusty
Reply

Maybe when the tracheal mites are moving from bee to bee, but otherwise you have the same problem: the mites are nicely protected inside the trachea.

I don’t know how commercial bumble bees are raised either. Come to think of it, I should know. Something for my list.

Nick
Reply

Rusty said, …”Did you ever see “Cane Toads: An Unnatural History (1988)”? It’s a 45 minute documentary (and one of the weirdest films I’ve ever seen.) It’s on YouTube.”

Yes! Perhaps my fave Aunt pulled that one out years ago. It is sick, scary, ‘this can’t be’, sort of weird! Seriously bad science on the importation of those to boot. I can still hear the pop, pop, pop while they were driving.

On the other side of the coin is a good ending story (as far as I know) on one of my childhood fiends of the pasture, thistles. I’m usually not much for weevils, but these guys bring a tear to my eye. When I think of the toils of my youth, slaving away at these things with hoe and spade, wearing my youth out (not saying that wasn’t part of Dad’s plan on handing over said implements)… and I could have been sitting there watching weevils dine!?!

Darn! http://www.agrisk.umn.edu/cache/ARL02967.htm

Nick
Kent, WA

Adam
Reply

Rusty,
You say “Although Stratiolaelaps will eat Varroa destructor, they prefer eggs and immature arthropods rather than full-grown adult prey.” Do you have references where it is confirmed they do in fact prey on the varroa? The only video I can find on it, from Niagara Beeway, shows them feeding on an adult varroa.
And are there any references about them only eating on their way to the ground or is this just through observations from fellow beekeepers?
Adam

Rusty
Reply

Adam,

You ask if I have reference confirming they eat adult prey, and then say the only video you’ve seen shows them eating adult prey. I don’t understand what you are asking.

Adam
Reply

Well, you say they prefer eggs and immature arthropods, so I’m wondering if you have any references other than that video, which shows them eating an adult.

Adam
Reply

Sorry, what I mean is there seems to be a lot of controversy about whether they actually do prey on varroa or not, and the searching I’ve done has only come up with that video. So I’m wondering if there is any actual research on it or is it just word of mouth?

Rusty
Reply

Right. I’ll need to go back through my sources and try to locate the passages. Most of my info about their behavior came from people who breed S. scimitus for sale, however there were several articles with sections about their interactions with Varroa. At least one referred to dismemberment of Varroa rather than eating, but one referred to actual eating.

Ken
Reply

Seems to me that drones have a significant part in killing Varroa. That’s why beeks use the drone comb. But the question that I keep asking is why drone? I get it that drones have several more days in encapsulated cells. They are also much larger and give these mites “super burgers with fries and a shake”.

So what drives these mites to uncapped drone cells? I am not a scientist or into mite biology. But it seems to me that there has to be some kind of “drone larva pheromone” that drives/directs these horrible creatures into drone cells to suck up all of the larva’s juices (hence fries with a “shake”).

Are there an labs working on this idea?

Rusty
Reply

Ken,

The way I understand it, mites have evolved to be attracted to drones because those extra few days in the cell allow more mite nymphs to grow to adulthood. Those young mites receive the same genes, so they too are attracted to drones. After many generations, most mites have the gene that attracts them to drones. I’ve read that the attraction mechanism is most likely a pheromone, so your theory is right on.

Nick
Reply

Another point everyone is missing, is that when this predatory mite reaches the soil, it likes to stay in the soil. I think that is great. The “soil” is where the small hive beetle pupates. There is already a treatment in the soil to take care of shb when it pupates, one problem solved. Think outside the box folks.

Rusty
Reply

Nick,

Do you know for a fact that S. scimitus will prey on small hive beetles? Most references list smaller prey items as the preferred food. If you have a reference, please let us know.

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