Determining the Cause of Your Dead Honey Bee Colony

Published on January 9, 2018

Dead Bees on Bottom Board

Are your honey bees completely dead? You might be wondering, “Why did all my bees die?” or “What caused my entire bee colony to collapse?” You might think, “I have lots of dead bees on the bottom board!” or you might notice that there are dead bees not only on the outside the hive in summer, but inside the hive as well. If this is you, read on…

It’s frustrating to think that you might just have to resort to telling your friends that it was “colony collapse disorder,” right? Well, instead of having to use that blanket statement, here are a few ways to diagnose your dead honey bee colony.

But first, there are a few general questions to ask yourself that will help you categorize your particular situation so you can more easily find your way to an answer:

What season are you currently in, weather-wise? (Did they die over winter or in the spring/summer/fall)?
Are your bees completely dead or is a large portion of your bees just beginning to die? (This article deals only with hives that are already entirely dead.)
Are the bees still in the hive or did they altogether disappear? (This article only discussed bees that have not completely absconded.)
Where did the bees die? Are the dead bees mostly inside of the hive or mostly outside of the hive entrance?
Do you see blatant evidence of disease or pests (other than the fact that your bees are dead), such as wax moths or wax moth larvae or wax moth webs, mold in the comb, fungus, spores, a chalky substance, water in the hive, hive beetles, etc?
Are there a lot of bees that have deformed or missing wings? Or do many of the bees have deformed abdomens?
Is there still a lot of bee bread (pollen) and honey stores in the hive?

Now, we can’t cover all of these scenarios in a single blog post, but we’ll at least address some of the most common situations.

Bees Died Inside the Hive (During the Winter)

The bees starved to death

Dead bees in cells

You can identify a hive that died from starvation by looking for dead bees inside cells with their butts sticking out. This is particularly common in hives that die in the winter. There are two probable causes in this situation. Firstly, it may have been too cold for the bees to leave the cluster to get to the hive’s honey stores. Secondly, bees may starve in a hive where the beekeeper harvests too much honey for their own purposes. This is highly avoidable – a beekeeper should only harvest honey in the spring, and save whatever honey is harvested in the summer and fall to put back into the hive during winterization.

The hive was too humid or condensation was out of control

Just like all other animals, bees exhale water vapor. In the winter, this causes problems, because that water vapor rises to the top of the hive, condenses and chills, and then drips back down onto the bees, causing them to freeze.

The bees froze to death

Your bees can freeze to death either by having cold water drip down onto them, as discussed above, or because the hive wasn’t properly insulated during the winterizing process. Be extra careful when preparing your hive for winter, and make sure that you have provided it with enough insulation and ventilation (but not too much!).

The bees had a high mite load in the fall and couldn’t handle the diseases

If your hive is infested with mites, there’s not much that you could have done outside of treating the hive with chemicals, which can be detrimental to the overall health of the hive over time. You can read more about treatment-free beekeeping and the varroa mite in this article from Keeping Backyard Bees.

The hive was completely covered in snow and the bees suffocated

In the winter, each snowfall will cover your hive at least a little bit, and can block ventilation, entrances, and exits. Check on your bees each time it snows and make sure to brush off these areas so that your bees are able to get in and out of the hive as needed, and that they can get the ventilation that they need.

If you want to learn more about preparing your hive for winter, check out our article about why bees die in winter and how to prevent it.

Bees Died Inside the Hive and/or Outside of the Hive Entrance (During the Spring, Summer or Fall)

Now, let’s move on to the other three seasons. The first thing to do is to determine the location of the majority of your dead bees. Are more of them inside the hive, or outside near the entrance?

Dead bees on top bar

If inside the hive, were the bees clustered towards the front, middle, back, top, or bottom of the hive, or were they spread out fairly evenly along the bottom board?

If outside the hive, were the bees strewn around in a semi circle around the outside of the hive entrance? Are they mostly drones (male bees), or a good mix of worker bees and drones? (Keep in mind, this article doesn’t deal with a simple drone eviction in late fall. It only covers scenarios where the entire colony has died.)

Next, look at the physical characteristics of the dead bees.

Did many of the bees have missing/deformed wings or deformed abdomens? This could be caused by a disease spread by varroa mites.

Are the bees’ tongues sticking out? This could be a sign of pesticide poisoning. To be sure of this, send the dead bees to a lab for testing.

Check out the brood cells.

Infected comb Are the caps of the brood pierced or torn partly open?This could indicate that the bees knew that the pupae were diseased or infested with mites, so they tore open the brood cells to allow the pupa to die.

Is there soggy, discolored or deformed larva in the cells? This could be caused by chalkbrood or other fungus or disease.

There are many reasons that a honey bee colony may die. The important thing is that you are able to identify why your hive died, and learn from the experience.

Resources:

beverlybees.com/how-to-autopsy-a-honey-bee-colony/

agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/animal-diseases/bees/a-guide-to-the-field-diagnosis-of-honey-bee-brood-diseases

uaex.edu/farm-ranch/special-programs/beekeeping/hive-pests-diseases.aspx

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Devon Rowley

With a background in writing and biology, joining the Beepods team just seemed like the logical choice for Devon. Not having much experience with bees, she loves learning about the fascinating creatures while editing the content that her teammates write and researching for her own pieces. When she’s got some spare time, Devon enjoys reading and spending time with her beloved cats.