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Diagnosing the Cause of Death

This is not a very uplifting topic for sure, but one of the most important skills in beekeeping is to learn from our mistakes, of which we all make many! The average annual hive loss rate is up to 44%. We all lose bees, especially in the first few years of beekeeping. There is tremendous value in what you’ve learned, in your equipment and drawn honeycomb. This gives you a tremendous boost next year! Your first year in beekeeping should be viewed as a learning experience. 

There are a variety of reasons hives can die. In most cases, they do not die quickly, but something happens weeks or months earlier that causes them to dwindle in strength over time, and eventually die. As you try to understand why your hive died, it is important to think through the history of your hive over the past 6 months.

 Here are some common causes of hive death, and what it looks like in a hive:

  1. Mites. The number one question I ask when someone's hive dies is: Did you treat for mites? What were your mite counts after treatment? Are you sure it worked? Did you continue testing every 6 weeks or so over the summer and fall? If mite counts rise above 2 per 100, they begin damaging the hive and spreading viruses. If you did not treat, or didn't treat until you had 10+ mites per hundred, or never tested later in the year, I usually blame the death on mites. You can also look on the bottom board of a dead hive. At times there is a layer of dead bees, and you can often see mites on the bees & all over the bottom board if you look very closely. 

  1. Starvation. Hives need lots of stored honey or syrup to survive the winter. If your dead hive does not have any honey stores, or you did not ensure they had adequate food stores in the fall, starvation is a probable cause of death. Bees dead with their heads inside cells is a classic symptom of starvation. A bit less common in the south, but if there are a few weeks with sub-freezing temperatures, bees can starve if they can't break the cluster and move to other areas in the hive that have honey stores.   Photo credit:
  1. Poor summer nutrition. This one is a bit more subtle, but if the hive did not have proper pollen and nectar resources in the 2 months leading up to the first freeze, they most likely were not able to raise healthy "winter bees" that live for several months over the winter. If that's the case, your hive will dwindle in population & eventually die over the winter as the worker bees reach the end of their shortened lifespan.

  1. Queenless hive or failing queen. If your hive became queenless , or had a failing queen late in the year, and the bees were not able to raise a new queen, the population will dwindle over the fall & die as the hive is not able to go into the winter with the proper population. A healthy queen, laying large amounts of brood in late summer and early fall is important to ensure a healthy hive going into the winter. See Failing queen or laying worker.

The following is a broad overview of conditions and causes most commonly found in backyard beekeeper “dead outs.” Some of these conditions are “seasonal” but so many of them could be in any season throughout the year.

Hive Condition: Dead bees head down in cells and/or a group of dead bees clustered around what “was” brood but has long since died.

Cause of Death: Starvation– The bees simply ran out of resources to eat. This can happen any time of year, but primarily at the end of Winter and early Spring (March.)

Hive Condition: Dead bees with no evidence of old brood

Cause of Death: Failing Queen in late Fall/early Winter. If your Queen wasn’t laying sufficiently in the later Fall months, you lacked the workforce to stock up on resources, warm the hive during cold weather, feed larvae, as well as groom and feed her. In Spring, Summer & Fall – the colony will quickly die with a failing queen simply because of no eggs being laid; no eggs = no nurse bees = no foragers = no food!

Hive Condition: Few bees milling around; may or may not still have a queen present along with an overwhelming bad fermented odor as well as little “worms” (looks like maggots) crawling in and around the cells.

Cause of Death: Small Hive Beetle infestation has overtaken the hive. Small Hive Beetles are a part of our everyday beekeeping life, but when not controlled they can and WILL cause your colony to abscond (leave) or die a slow miserable death. Staying on top of SHB is truly one of the easiest tasks we face. It doesn’t require any testing and all effective methods of control are mechanical and don’t require medication or pesticides be placed in out hives.

Hive Condition: Few bees or no bees; “worms” and moths crawling around, cocoons and webbing built on the tops, sides, and faces of frames.

Cause of Death: Overrun with Wax Moths because of Neglect Yes, I said it… Neglect! Wax Moths are opportunistic – meaning, if they are allowed to come in and take over where the bees had previously been, they will completely destroy old comb and even eat into frames and the boxes. The nasty webbing mess is completely preventable. When you have a colony in decline, ideally address the problem immediately. If it’s obvious the colony isn’t going to make it, break the box down and store the equipment for future use. A dead out left in your bee yard will quickly turn into trash if not addressed.

Hive Condition: Some dead bees or No dead bees and no resources.

Cause of Death: Robbing– If the rims of the resource cells (honey/nectar) appear to be ragged or torn and you find a lot of wax debris on or below the bottom board, the colony probably didn’t die of starvation but instead was robbed of all of its resources. This most often doesn’t happen to “strong colonies” but rather colonies with reduced populations due to virus, diseases or failing queens (causing decreased population.) See a picture of Robbed frame below. Photo credit:

Another Cause of Death could be: Queen failed– The queen was present but stopped laying; if left unnoticed the colony was doomed. With no new brood to carry on, they had no new house bees to clean cells, warm the brood nest, feed larvae, feed and groom the queen, build wax, ripen nectar, or guard bees to protect the colony. In turn no bees aging into foragers to bring in resources for the colony to survive. IF – You spot an excess of dead drone brood cells (capped or not) it is possible your queen became a “Drone layer.” What is this? A Drone laying queen means, at some point she ran out of sperm; either she wasn’t mated well or she simply aged out (ran out of sperm). Either way when this happens the colony is hopeless. Recognizing they need to replace the queen, the workers have no “fertilized” eggs to make a Supersedure or Emergency cell at this most crucial time. Colony ultimately dies.

Cause of Death could be: Absconding (the colony left) Often when colonies are sick and failing, starving or have high mite loads, they will just leave! Would you live where the conditions are so bad you can’t stand to stay? Odds are those bees didn’t survive long once they left but they really didn’t have a choice…die if we stay, die if we go.

Hive Condition: Some bees still milling around but Queen long gone, no brood or bad/sick looking (white, black, shriveled) dead brood, maybe an overabundance of nectar but no nurse bees present

Cause of Death: Possible disease or virus present– When a colony dies from disease it can be very difficult to pinpoint the cause. Your “evidence” is most likely gone by the time you find the dead out. BUT – it is very important to know the most common among those we experience. It would take a small novel for me to list the description and explanation of the viruses and diseases Honey Bees are subjected to. For a very good reference guide CLICK HERE to learn more.

Note: Most viruses and diseases are preventable by controlling Varroa Mites. To learn more about Varroa Mites and how to stay ahead of them CLICK HERE.

Another Cause of Death could be: Swarming - Yes, swarming can cause death of a colony! When a colony prepares to swarm, “in theory” they will create a viable queen cell (Daughter Queen.) Depending on how many swarm cells were produced and how well they were fed has a huge bearing on the viability of the “queen left to take over!” OR – the daughter queen left to be mated and never returned, leaving the remainder of the colony that didn’t swarm to fend for themselves, often with bad results.

Hive Condition: Dead Bees on the bottom board (moist and rotting)

Cause of Death: Moisture– If the colony didn’t have sufficient ventilation in the Winter, condensation can occur. Water vapor rises; as it condenses and chills it will then drip back down on to the bees and cause them to chill/freeze. Mold and mildew is also a problem with an overabundance of moisture. It won’t likely kill the bees but makes for a very poor environment for your colony and they will often abscond if left unresolved.
Hive Condition: Dead Bees inside the box, on the bottom board, on the landing and on the ground in front of the hive

Cause of Death: Possible insecticide, herbicide or pesticide poisoning A good indicator that bees have been exposed to poison is evident if you find a bee dead with her tongue sticking out. Sometimes a kill can be over a period of time if the bees simply foraged in an area recently sprayed. In this case, the forgers may die off slowly and/or carry the poison into the colony causing a rapid kill.

There are so many “if’s, and’s and but’s” in forensics of a hive. BUT – truthfully, it all boils down to 1 BIG point – Doing regular hive inspections and staying on top of the condition of your bees! When we do the bi-weekly checks and quarterly Hive Inspections on our bees, we are able to see if something needs to be addressed. The problem starts when we DON’T react to a situation, then a month later we are faced with the reality that our colony didn’t recover without our intervention. Education is the best gift you can give your bees – commit to taking every opportunity to further your education through club meetings, seminars, webinars and in-person classes. The joy of being successful at keeping healthy thriving bees will far exceed the cost of time and money. Happy Beekeeping!

By Chari Elam/Blake Shook

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