mason bees

Mason bee covered in mites

I try to remain vigilant for mason bee mites and I use recommended control measures for limiting their impact on the few mason bees I have. But earlier this year I saw my first really bad case of hairy-footed mites on the backs of two newly-emerged mason bees.

The bees in question emerged not from my mason bee houses, but from a little moisture drain on the bottom of a bedroom window. I heard the window buzzing and I was perplexed as to what was going on. After several hours of commotion, two masons emerged into the space between the window and the screen.

The adult female must have crawled into the little drain hole on the outside of the house and, the following spring, the new-born bees emerged through the window frame. I thought the whole thing was adorable until I took a closer look: each of the bees was covered with what looked like sticky brown fluff—in other words, an infestation of hairy-footed mites.

The infestation was so bad that I suspect mason bees have been nesting in those drain holes for more than one season. I tried to photograph them through the glass (which didn’t work so well) but you can see the coating of mites, which looks something like a brown shearling vest. One of the bees was rising up on its hind feet trying to fly, but the weight of the mites was overwhelming.

The hairy-footed mite (Chaetodactylus) is also known as the pollen mite. A special nymph stage, called a hypopus, rides around on the back of an adult bees until it finds a source of pollen to eat. But frequently the adult bee unwittingly takes the mite home. The mites reproduce within the larval chamber where they eat the pollen provisions the bee left for her own offspring. With no food stores, the bee larvae die. Sometimes the mites eat the bee egg or larva as well. If you open a mite-infected tube, you can often find a mass of orange-colored mite debris filling a cell—a sure sign they were busy eating and reproducing for a long while.

In the spring, surviving bees crawl through the nesting cavity where they pick up a great many of the phoretic nymphs that are designed to grip onto the bee and not let go. From there, they are carried to flowers or into new nesting cavities.

The mites are native to North America and can infect many of the bees in the Megachilidae family, which includes the mason bees, leafcutters, and carder bees. They prefer damp environments—one reason they are proliferating in the coastal Pacific Northwest.

Rusty
HoneyBeeSuite

Newly emerged mason bee covered in hairy-footed mites.

25 Comments

  • Poor thing!! Can you do anything for the poor bees that you find in this condition? Do these kind of mites affect honey bees too?

    • There’s nothing you can do once it happens. The mites have special feet that clamp into the bee very firmly, and most chemicals that kill mites also kill bees. It’s best to prevent the mites in the first place.

      And, no, honey bees do not get this type of mite and this type of bee doesn’t get honey bee mites. They are very specific.

      • Thanks so much Rusty! I LOVE your site and pictures. It’s been SO helpful since I just getting started with my bees.

      • Well here goes nothing, The mites that are after honey bees are sometimes repelled by using powered sugar. Might be worth it to try some on a few bees to begin with. Hope this helps.

        • Julian,

          Honey bees are not repelled by sugar, but they do try to groom it off their bodies. In so doing, they may remove a few mites, but most mites are securely anchored under the abdominal plates where they cannot be removed by the bees.

          Pollen mites grow inside the sealed brood cavities along with the bee pupae. You have no way to get powdered sugar in there and the pupae have no way to remove it.

  • I’ve a little bee house for mason bees in my garden here in England and ‘Ive noticed 2 mason bees that are flying around and frantically landing and trying to dislodge the mites on their backs and heads… they look just like the one in your picture… should I take apart the bee house and clean it??
    Feel so helpless for them… 🙁

    • Alexandra,

      Over here, it is recommended that you change the tubes every two to three years to avoid a build-up of parasites. Some people line the tubes with parchment paper. Then, at the end of summer, they pull out the parchment and put the cocoons in cold storage until spring. I think you can disinfect the tubes, although I’ve never seen a good description of how to do it.

  • Rusty,

    I guess now is a good time to ask this; could one put frames or bee blocks in a container and burn sulphur like is done to make sulphured apples? Seems it would sterilize well if it didn’t harm bees.

      • I have burned sulfur before and it is an extremly toxic chemical that my grand father used to use when he got sprayed by a skunk. He would place his clothes under a upside down bushel basket an a add a small amount of sulfur in a fire proof container and lite it. When it was done burning, his clothes didn’t smell any more .

  • I’m having this problem just now. My first year of mason bees have not long emerged and I have noticed some small yellow crawling things on the outside of one of the tubes. There was actually a dead bee half out the tube and within a day the full dead bee was covered in mites. I managed to knock most of these off with sand and I got rid of the dead bee. I’m at a loss at what else I can do.

    I don’t know much about mason bees but I have noticed that when the weather turns rainy, the female bee sits inside her tube. She has made a wall of mud and tucks herself in behind it while leaving a head sized hole to look out of. Do the female bees remain with her eggs and just end their life in the tube?

    • Jill,

      I don’t know what you can do at this point. Folks in the UK tell me the mites don’t do much harm to the bees and that the bees can live side-by-side with the mites.

      Most bees do not fly when it rains, but seek cover. The females will often stay with the nest until the weather clears. The female will not remain with the eggs, but will probably die while out foraging for pollen or nectar.

  • The tubes are filled and the mason bees have stopped activity. Now some of the tubes are becoming empty.

    Is it because of mites or some other insect? What can I do?

    • Pat,

      It could be parasitic wasps, birds, or any other predator. As soon as the tubes are filled, take them inside and store in a cool, dry, predator-free place until next spring.

  • How do you eliminate mites from the cocoons before you store them for the winter?

    I read somewhere if you mix 1/4 cup of Clorox bleach with a gallon of water, soak the cocoons for 2 to three minutes to kill off the mites without harming the bees in the cocoons. Is this true?

  • Can the mason bees remove the mites by themselves? I have lots that are absolutely covered in them and are attacking the ones that don’t have mites. But we also have ones that are fine and some with maybe a few mites. Can they remove them from each other or themselves??

    • Lexi,

      They can probably remove some of them. Pollen mites aren’t like varroa mites because they don’t bite the bee. They just use the bee to get a ride to a flower where they can jump off and get a ride on another bee and into its nest. Inside the nest, they eat the pollen. The problem with mites on adult bees is that sometimes the mites are so numerous and heavy that they make flight impossible. If you catch the bee, you can wipe most of them off with your finger.

  • Rusty, my poor bees are literally covered in the mites. They can’t even fly. I have cleaned out the my bee houses but I just don’t think I could face using them again just in case. I have tried wiping the mites off but they seem stuck on. The bees have just been landing on my hands and letting me try. I am heartbroken.

    • Maria,

      I agree it is heartbreaking to see. I’ve begun using new tubes and emergence boxes each year.

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