Did mites kill my bees?

You went into autumn with an exuberant and populous hive. You weren’t worried about them because they had a first-year queen and loads of honey and pollen. You counted your mite drop and it seemed okay—you saw a few mites but not many—so you dusted the bees with powdered sugar just to be on the safe side.

Somewhere toward early spring you decided to check the colony’s food supply, just in case. You even prepared some candy boards as an insurance policy. So on the first warmish day when you thought it was safe to open the hive, you did. But to your amazement, no one was home.

What you found was an empty hive with very few dead bees and frame after frame of untouched honey. Or maybe you found no bees and no honey either. Instead, all of the frames that had been full were now empty with ragged and torn edges. What went wrong?

The very first thing I would suspect in a situation like this is Varroa mites. Mites can take down a colony quickly, and the mites that you count on a sticky board are just the tip of the iceberg. But to be sure—or at least more sure—here is a list for your post mortem:

  • If there are very few dead bees in your hive, it may mean the colony worked hard at removing them until the last minute. Try to find some dead ones on the bottom board, alighting board, or even on the ground nearby. Sift through them and look for bees with deformed wings.The presence of many deformed wings is a good indicator of Varroa.
  • If you have a bottom board or Varroa tray in place, look for mites. If the colony died from mites, you will find mites in the debris.
  • Look for frames of honey. A hive with plenty of honey and no bees can be a sign of Varroa. A hive with no bees and honeycombs with jagged edges indicates a weak or dead hive that was invaded by robbers, which can also be a sign of Varroa.
  • Examine the brood frames. Adult bees that died while they were emerging, or just before, may have been weakened by Varroa. These bees will have their heads facing up. (Bees that starved while searching for food in the cells will have their tail ends up.)
  • Hold up the empty brood frames with the sun at your back so you can see inside the cells. If you find bright white deposits adhering to the inside of brood cells, you can be sure of a Varroa infestation. These white spots are patches of mite excrement that contain about 95% pure guanine, an amino acid.

Mite feces
The white mass in lower right is mite feces. Photo by USDA ARS

If you conclude your bees died of a Varroa infestation, review your management strategy and try something different next year. Mites can be handled in many different ways, but you must be diligent. If you do nothing—or next to nothing—the mites you reared will soon spread to other colonies, both feral and managed.

Rusty
HoneyBeeSuite

Comments

Andy Brown
Reply

I suspect you diagnosed what happened in my hive. I’ll have to look for some of the signs you describe. If it was varroa is there any problem with giving the frames of honey to the new packages of bees I’m getting in a few weeks?

Rusty
Reply

Andy,

No, no problem. Once the bees die the mites can’t survive either, so the equipment is clean.

Rich
Reply

This is exactly what happened to me. My question was exactly what Andy asked. Looking forward to trying this again starting on 13 April. Thanks again, Rusty.

~Rich

John
Reply

Life was complicated this past year. I was distracted in the spring and fed my weak and new colonies not enough. Another year of near-drought brought them thru late JUN and early JUL pretty light on nectar collections. My major failure, though, was mite treatment a bit too late in the year. My old guideline used to be harvest by State Fair time (Labor Day). Now I’m moving that up and beginning late season mite treatment a bit earlier. I’m also working on some new sticky board devices that I can place higher in the hive and not just at the bottom. Mites falling off bees in the third brood chamber aren’t like to fall all the way to the bottom.

Rusty
Reply

John,

Interesting idea; I would never have thought of sampling higher up. I too keep treating earlier. Now I like to have it done by the end of August.

eric
Reply

I lost two hives this winter, one a swarm that probably crashed from varroa.

Is there a page on your site where you map out your varroa treatment process for the year?

And what is your opinion about Hop Guard after your ups and downs with it?

thx, eric.

Rusty
Reply

Hi Eric! Haven’t heard from you in a while.

Your question about HopGuard is timely. I’ve been sitting on a post, more or less waiting to see how my bees came through the winter. As of now it seems like everyone made it. It turns out that HopGuard saved the day for me, something I will explain in my post. I’ll try to get it up this weekend and, at your suggestion, I’ll also try to outline my mite philosophy and regimen. It’s not very complicated, really.

Thanks for these ideas.

Rusty
Reply

Andy,

Interesting photos. The queen made it until the end but there weren’t enough bees to keep themselves warm. Why? It’s possible the queen was failing and not laying properly, but that wouldn’t be my first guess. I will stick with mites (and the resultant viruses) as my first guess. The combination probably depleted the population until it wasn’t large enough to keep itself warm. Very sad. It looks like some spotty brood in the background. They were trying until the last.

Andy Brown
Reply

Thanks for having a look. I ended up with frames of honey from three different hives, so I guess I’ll have to read up on how to make use of that with the new bees.

Art
Reply

I had good results in mite control by selecting “mite resistant” breed of bees, namely Buckfast. I get the queens from R-weaver apiaries. In several years I never had to treat them for mites and never lost a colony to mites. It doesn’t completely eliminate mite problem, but bees seem to keep it in check themselves. I don’t know if the fact that I live in Florida and bees fly here pretty much every day of the year has anything to do with that but I think it is worth trying.

Rusty
Reply

Art,

I’ve never seen any indication that Buckfast bees are at all resistant to varroa mites. Buckfast bees were bred specifically to resist tracheal mites. In recent years, however, tracheal mites do not seem to be as much of a problem as they used to be. In fact, some labs don’t even do tracheal mite testing any more. While Buckfast are excellent bees—and I’ve used them myself—varroa mite monitoring must be continued.

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