Learning From Deadout Inspections

Beekeeping brings so much joy to so many, but also has its challenges. We have looked in detail at the various threats to bees. Losses are always difficult for the beekeeper but, while all beekeepers lose bees sooner or later, such an event presents an opportunity to learn and a chance to reduce the chances of the same happening in the future.

Even when an entire colony is lost, there is opportunity. The inspection of a “deadout” (beekeepers use colorful language!) is an often overlooked aspect of beekeeping. Sometimes the disappointment is so great that the beekeeper just cleans up and moves on to other hives, with just a few minutes spent trying to figure out the cause.

But a more thorough investigation can tell a beekeeper a great deal about the health of his or her hives and what management practices may be required or changed to improve colony health.

Here we discuss the process of inspecting a deadout and some of the things you can learn.

The Process

When a deadout is discovered, the understandable sadness should be followed by a logical process of discovery.

  1. Observe the Hive Surface: Check the surface and the area around the hive and make note of any bad or unexpected smells. Are there dead bees, a complete absence of bees, or a disturbance around the hive?
  2. Remove the Outer Cover: Make note of anything under the outer cover, such as mold, moisture or something other than bees living there.
  3. Remove the Inner Cover: Observe anything unusual on the inner cover and the top bars of the hive. Look down through the frames to make note of a cluster, if there is one, but do not remove the frames yet.
  4. Remove The Hive Boxes: Remove them one at a time and carefully set them aside. Examine the bottom board first. The condition of the dead bees on the bottom board, their age, and location are very informative.
  5. Inspect the Lowest Box: Return to the hive body that was resting on the bottom board. Begin working through the frames and then continue on up through subsequent hive bodies to the top box.

As you move through the hive, ask yourself questions.

  • Where was the food located on the frames, in relation to the location of the cluster?
  • Did you find a queen?
  • Were there young bees or older bees clinging to the frames?
  • Were the dead bees piled under the cluster or were they lining the entrance to the hive at the front of the bottom board?
  • Did you find any brood?
  • When you examined the frames what did you find in the cells (dry scales easily removed from the cell, mite excrement)?
  • Were there signs of robbing – chewed, ragged edges to cells or signs of other critters such as mice?

Be sure to look for signs of Hairless Black Bee Syndrome, Deformed Wing Virus (DFW), European foulbrood (EFB), K-Wing, and snot brood.

Dead Bees on the Bottom Board

In a winter cluster, the oldest bees are gathered at the outside edges, usually something like the outside two inches.

When temperatures fall below 41 degrees on the outside, bees can become too cold to move into the cluster for warming
At this point they can lose their grip, fall to the bottom board, and die. Sick bees will lose their grip even sooner.

This results in a pile of bees located directly under the cluster. Sometimes this is a winter sign of Parasitic Mite Syndrome (PMS), so be sure to check for signs of mites. This is also a good reason not to knock on the side of your hive to listen for a buzz that tells you the colony is alive.

When enough bees have fallen away from the edges of the cluster, the cluster size shrinks and it cannot expand to reach food. At this point, if the weather remains cold long enough the bees will not be able to reach food stores and can die from starvation and cold, even with plenty of honey in the hive.

Dead bees lining the entrance may have died as a result of poisoning
They were trying to leave the hive all at once and perished in a pile, at the front entrance.

Be sure to look for two separate clusters as this may be a sign of tracheal mites. Bees with tracheal mites have difficulty breathing because their breathing tubes are blocked. Consequently, they cannot cluster normally and spread out in an effort to breathe.

If you found bees lining the entrance to the hive at the front of the bottom board, you will want to examine them to see if their tongues are sticking out. Bees exhibit altruism in many ways by dying away from the hive so as not to spread disease, mites, or create additional work for the colony needing to remove dead carcasses. It is said that in the summer, a large, healthy hive loses 500 bees per day, but most die away from the hive and the beekeeper rarely observes this scale of loss.

The Queen

Were you able to find the queen? It’s possible she died late in the fall and the colony was doomed from the start. Or possibly she was not healthy and laying properly.

Look closely at the dead bees on the bottom board to see if you can find her. It’s well known that queens are not living as long as they used to and your queen may have died in the fall.

Though not proven, there is growing evidence that shorter lifespans are from genetic defaults due to inbreeding. In general, locally raised queens will outperform those obtained from commercial queen farms because they are better adapted to your location.

Diseases, Definitions, and Mite Poo

As a beekeeper observing a deadout, you are like a detective at a crime scene. Is there a history to go on or are you handicapped because you failed to take good notes during the season? Taking good notes can greatly assist the beekeeper-turned-sleuth.

Viruses are vectored into honey bees when mites create feeding sites in the pupa. The foundress mite carefully maintains and keeps the feeding wound open, so her offspring can readily feed on the developing bee’s hemolymph. Nurse bees cleaning up dead brood can also spread the viruses to other brood.

To assist with determining the cause of death, consider sending a sample of dead bees in to be tested for certain issues. Visit the USDA’s instruction page for sending dead honeybee samples in here to learn more.

Chronic Bee Paralysis Virus (CBPV)

Also known as hairless black bee syndrome, this condition is only found in adult bees and not the larvae. It presents itself in crawling, trembling bees at the front of the hive or on the ground. Adults lose body hair and appear greasy (shiny).

In a dead out you may find these bees among the dead on the bottom board or clinging to comb in the cluster of bees.

K-Wing and Deformed Wing Virus (DWV)

These indicators point directly to PMS (Parasitic Mite Syndrome) and the Varroa mite. DWV appeared in the U.S. at about the same time as the mites. The very distinctive symptoms present in emerging adult workers. Bees are stunted and their wings are twisted and deformed, never becoming functional.

The condition often appears in drones first and these bees are unhealthy and only live a few days. Colonies exhibiting signs of these viruses usually collapse and mite control is the key to prevention.

If your colony died in the fall (Nov or Dec in the north, for example), mites should be the first suspect on your list. In the fall, the ratio of mites to bees increases and colonies infected with Varroa often die.

Another sign that Varroa can be suspected is if you only find a few dead bees in the hive and lots of honey. The bees that were not infected continue to remove dead bees and maintain the hive as the population in the colony declines.

Be sure to take a close look for guanine deposits when examining the frames. This is a white deposit located at the open end of the cell. You can find these by holding the frame up with the sun at your back. They will appear as bright white deposits because the mites go to the same site to defecate and thus the deposit builds up.

European Foulbrood (EFB)

European Foulbrood is caused by bacteria and affects young larvae. The cells of dead larvae are not capped, as is the case with American Foulbrood (AFB). The larva will be discolored, turning from yellow to brown and there is often an associated sour decay odor. The larva will also appear twisted and will not pass the “ropey” test that is used to check for American Foulbrood.

When examining the frames, use a small pick such as a dental tool to dislodge any black scales found in the cells. Dried larva that has died from EFB leave a scale that is relatively easy to remove. AFB leaves a similar scale but it is very difficult, if not impossible, to remove.

Snot Brood

This term is used to describe a spotty brood pattern that exhibits a mixture of brood disease.


New beekeepers may find mold in the hive and conclude that it was the cause of the loss of the colony. Don’t let this confuse you. You will rarely find mold in a healthy colony and the mold normally appears after the colony has died.

Drawing Conclusions

You won’t always be able to conclusively determine why your colony died. But by carefully following the steps outlined at the beginning of this lesson you should at least be able to come up with some ideas.

When combined with good notes taken over the course of the season and a little experience, you will often get a good idea as to what brought down your hive. Once you have determined the cause you can make changes in your management practices to help alleviate the problem in the future.

One last thing that will contribute immensely to your success as a beekeeper. Keep learning!

  • Learn the life cycle of the honey bee inside and out
  • Understand the ebb-and-flow of the colony through the year
  • Then, learn the Varroa mite life cycle and how it applies to life in the hive

Once you fully grasp these things and understand how they fit together you will be well on your way to solving the riddle of one of the greatest obstacles to present-day beekeeping.