How to clean up from Nosema apis

Cleaning up after a Nosema apis outbreak is no easy chore. Your best course of action is to prevent an infection in the first place. My second piece of advice is to make sure it actually is Nosema apis that you are trying to clean up. It is easy to confuse simple honey bee dysentery with Nosema apis, so you will want a positive identification before you start. Identification requires a microscope and some training, or you can ship your sample to a lab.

Both Nosema apis and Nosema ceranae are transmitted by resistant spores that can survive long periods. The disease is transmitted when honey bees ingest the spores. This can happen when bees are cleaning the combs or other parts of the hive.

Since Nosema apis usually causes dysentery-like symptoms such as distended abdomens and defecation in the hive, it can be confused with normal wintertime honey bee dysentery which also causes distended abdomens and defecation in the hive. But with Nosema apis the spores pass through the digestive tract along with the feces. When other bees try to clean up the mess, they become infected as well.

Hive bodies, bottom boards, inner covers or any other wooden parts of the hive can be fumigated with various chemicals—such as glacial acetic acid—or they can be scorched with a blowtorch. It is best to first scrape all the wooden surfaces to get the thick stuff off, then scorch your woodenware and your hive tools with the torch.

A number of different chemicals can be used to fumigate combs, but none are very practical for the hobby beekeeper. They can also be irradiated or treated with ozone—also impractical and expensive if you have just a few hives. The simplest way to disinfect is with heat, but that isn’t easy either. Randy Oliver pieced together the following data that he found in a variety of research papers. The table shows time and temperature needed to disinfect Nosema-infected combs with heat.

Degrees F Degrees C Time
140 60 15 minutes
120 49 24 hours
104 40 5 days

Beeswax will melt at about 145°F (63°C), so if you decided to use high heat, you need a way to monitor and control it. As with your woodenware, I recommend that you first scrape the frames to get off as much residue as possible before you treat with heat.

All in all, prevention is far easier than trying to clean up. The best defense against Nosema or any other bee disease is to maintain populous healthy hives.

  • Maintain large colonies going into winter. Combine small colonies with larger ones as long as they are all healthy.
  • Provide good ventilation so hives stay dry inside.
  • Ensure that colonies have adequate supplies of both honey and pollen going into winter.
  • Keep hives in a sunny winter location to encourage cleansing flights.
  • Treat for Varroa mites. Bees weakened by mites are more susceptible to a variety of diseases.
  • Continually replace old combs with new ones to prevent disease build-up.

If you believe your bees have Nosema or you want to prevent an infection from spreading, you can treat your colonies with fumagillin according to the package directions. Fumagillin is an antimicrobial agent isolated from the fungus Aspergillus fumigatus. The fungus is found naturally in soil and decaying organic matter. Fumagillin is sold under the brand name Fumidil-B or Fumagilin-B and is fed to honey bees in syrup. Fumagillin prevents the Nosema spores from reproducing in the honey bee gut, but it is unable to kill the spores.

Rusty
HoneyBeeSuite

Aspergillus fumigatus. Photo by CDC/Dr. Libero Ajello.
Aspergillus fumigatus. Photo by CDC/Dr. Libero Ajello.

Comments

Patrick
Reply

So you do essentially discard any comb from an infected hive? I’d always thought that kind of drastic response was reserved for foulbrood.
Tough decision.

Rusty
Reply

Well, you can heat-treat the combs according to the chart. The problem is this: if you re-use combs without disinfecting them, you have to constantly treat with fumagillin. If you stop treating, the bees will come down with Nosema, usually in the first winter following the withdrawal of treatment. The spores can remain active for years. Some people do it like that and just keep treating and treating and treating. Is it really a tough decision?

Patrick
Reply

How do you go about obtaining positive identification? Lacking a microscope and requisite training, is my best option to send in dead bees for analysis? If all the bees have been dead for a while, is there any hope of getting a positive determination?

Rusty
Reply

Patrick,

I would contact your local extension agent and ask where to take/send a sample. You need about 50 bees, if I recall, and they can be frozen. Like I said, the spores can last for years, so I don’t think the bees being dead for a while is a big problem, as long as they’re not decomposing.

Bill Castro
Reply

Experience has shown me that once the main nectar flow comes on, these types of problems, dysentery especially, usually clear up quite quickly. Ozone has been recently shown to also clear up possible spore and bacterial contamination on equipment, including foundation.

Rusty
Reply

I agree with that. Everything seems to go away once the flows are on.

Brian P. Dennis.
Reply

Field test for nosema:

Take a sample of about 30 bees. Take each bee & remove the head using tweezers to sever the mid-gut from the head. Grasp the last segment & sting with tweezers and, gently holding the thorax, slowly and firmly pull away. Place mid-gut on a white surface. If it appears tan coloured and wrinkly, it is healthy. If it is white & smooth, it probably has nosema.

Rusty
Reply

Brian,

I had forgotten about this test. Yes, this really works. Thank you.

Emily
Reply

Fumidil B is unfortunately no longer approved for sale in the UK, so we UK beekeepers now have to concentrate on good husbandry practices to protect against nosema.

Jeanette
Reply

On a related note, scientist Noah Wilson-Rich is planning to field-test an antifungal vaccine for honey bees this summer. The hope is that the vaccine will prevent Nosema.

Bob
Reply

If comb is treated with heat or ozone, how do you prove when the spores are dead.

Rusty
Reply

Bob,

There are documents available that tell you time vs. temperature and/or time vs. concentration. If you go by the charts you will be fine; you don’t need to test afterwards.

Bob
Reply

Where can I find a chart for the required rate of ozone flow (mg/hour) and time of treatment?
Also, it would be good to be able to verify that the treatment was successful (dead spores) be for reintroducing the comb to bees.

Rusty
Reply

Bob,

Don’t really know. Here is a powerpoint with a lot of information about ozone disinfection: http://www.ars.usda.gov/SP2UserFiles/Place/54280500/Ozone%20CA%202011.pdf. In my opinion, it’s not worth it for for N. apis, only N. ceranae. Do you have confirmation of N. ceranae? How many hives do you have? It might be cheaper to scrap the hive and start again. Ozone is nasty stuff.

Craig
Reply

Dipping wooden ware in paraffin wax seems to be promising, in theory.

Add micro-crystaline wax or resin.

It’s relatively cheap to set up, you can heat it to well over 300 degrees and it won’t damage the wood. (The wood can’t burn, since it’s submersed, so there’s no air for combustion.)

About the only thing it won’t kill is AFB, which needs something like 375 degrees for 24 hours. This would be dangerous since you can’t leave the thing unattended.

Most backyard setups are pretty much a larger version of a turkey fryer, with about the same level of risks in using them. You’d need a fire extinguisher, rated for grease fires, close at hand.

angel-myrealname
Reply

Questions: I was thinking about ways to heat sterilize frames, boxes etc to above 140 F for 15 mins without messing up my oven. Yes, that was an idea instead of a torch. [Boxes like a clay kiln idea.] But then just read dipping woodenware in paraffin wax heat it to well over 300 degrees and it won’t damage the wood. (The wood can’t burn, since it’s submersed, so there’s no air for combustion.) Like idea of dipping/soaking, but not paraffin
[natural wax residue wouldn’t bother me].

Here’s the questions > what if I used a metal small horse trough/tank set on blocks both ends and have a wood fire to heat just plain water. Then boil empty boxes etc for 15 mins or more. Do you think that would sterilize good enough? Would any tiny natural wax residue coating be safe since it was boiled too? I am trying to plan ahead for all > emergencies, medical, items, daily/monthly needs and well being of a hive of bees. before I take on the responsibility for their lives.

I have to be creative on costs and way things can be creatively done, finding work-arounds for my disabilities and so my service dog can help me with. [Yes she will have a bee suit; I am designing so no stings on her nose or toes]
I love your site it’s one of the best I can find.

Rusty
Reply

Angel,

Thank you for the compliment. But I have to say, I believe you are way over-thinking this. I wouldn’t worry about sterilizing bee boxes unless you actually have to do it. In all my years of beekeeping, I have never had to sterilize a box and never had a Nosema outbreak. If I have one in the future, I will examine the condition of the equipment before deciding what to do. The contingency you have to face probably will not be one you anticipate, and the possibilities of things going wrong are endless.

If you want to study in advance of getting your bees, study bee biology and the life cycle of Varroa mites. Nothing will help you more.

But anyway, if I had to sterilize a box today, I would use a torch.

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