How to Diagnose a Deadout: The Spring Autopsy

A dead hive is a written record. The colony was alive in October and dead by March, and the sequence of that failure is preserved in where the bees are, what they were touching, what they left uneaten, and what has moved in since. The reason to read it is not sentiment. It is that the same yard, the same equipment, and often the same management will produce the same result next winter unless something specific changes, and you cannot change the right thing until you know which thing it was.

The most common mistake is to conclude "they starved" from the presence of dead bees in cells and stop there. Starvation is nearly always a proximate cause with a real cause behind it: a colony too small to reach its stores because varroa shortened the lifespans of its winter bees, a cluster isolated by a cold snap with honey two frames away, a queen who failed in September so no winter bees were reared at all, or an autumn where the beekeeper misjudged the weight. Those four situations look similar from the top of the box and lead to four different fixes.

The second mistake is cleaning first. Bees get shaken out, frames get stacked in a new order, the bottom board gets scraped into the grass, and the evidence is gone in four minutes. Photograph first, read second, clean third.

The debris on the bottom board is a season in miniature and it costs nothing to read.

A deep layer of dead bees is normal in any deadout and by itself means little; bees die all winter and the living carry them down. Very few dead bees in a hive that had a large fall population is a loud finding: the bees left and did not come back, which is the classic varroa collapse pattern.

Wax cappings, chewed and scattered across the board and out onto the landing area is robbing evidence. Robbers tear cappings open and drop the wax, and the crumbs pile up like sawdust.

Mouse droppings, shredded comb, and nesting material answer their own question. So does the smell.

Silky webbing, tunnels through the debris, and cocoons in the corners are wax moths, which are almost always secondary; the full story is in the wax moth guide.

Small dark beetles and slimy comb point at small hive beetles, covered in the small hive beetle guide, which likewise mostly finish colonies rather than start them.

Mold on the board and up the walls, plus water staining, points at a moisture problem, which is one of the few causes you can eliminate outright with equipment.

The cluster is the single most informative object in the hive. Two dimensions matter: where it sat, and how big it was.

Cluster jammed against the inner cover, empty comb below. The colony ate its way up and ran out of ceiling. Classic starvation in a hive that did not have enough stores or had them in the wrong place.

Cluster off to one side or the front, capped honey on the far side of the box. Cluster isolation. The colony had food and could not reach it, because moving across cold comb in a hard freeze kills bees. This is a different failure from starvation and it has different fixes.

Cluster in the middle with capped stores all around, small. Not a food problem at all. The colony dwindled below the size it needed to keep itself warm, which points at queen failure in the fall, at winter bees damaged by varroa, or at both.

Large cluster, dead in place, honey adjacent. Suspect an acute event: a hard sudden cold snap, a soaking, a pesticide event, or a colony that got wet and chilled.

For size, use fruit. A softball-sized cluster in January was already failing in November. A cantaloupe or larger cluster was a viable colony that hit something. The distinction between "it dwindled" and "it died all at once" is most of the diagnosis, and it is why we ask you to note the size before the frames get moved.

Bees with their heads down in empty cells and abdomens sticking out is the most recognized sign in beekeeping, and it is genuinely diagnostic of starvation: those bees died crawling into cells looking for the last traces of food. What it does not tell you is why the food ran out, and that is the question that matters.

Flavor one: the pantry was empty. No capped stores anywhere in the box. The colony went into winter too light, or a long warm fall let them eat through reserves, or the beekeeper harvested too much. The fix is weight: know what a wintering hive should weigh in your region, heft the back of the hive through the winter, and feed solid feed when it gets light. Candy boards, fondant, and dry sugar are the tools for that, because syrup is useless once it is cold; the options are in the winter feed guide and the emergency version is a candy board like the BeeCastle 10-frame candy board ($37.99) set directly over the cluster.

Flavor two: the food was there and they could not get to it. Capped honey on the outside frames, or in the box above, with a starved cluster below or beside it. In a hard freeze bees will not break cluster to cross cold comb, so a colony can starve inches from food. The fixes are structural: consolidate stores next to and above the cluster in the fall rather than leaving them at the edges, keep the colony compact enough to hold heat, reduce heat loss with a wrap such as the MayBee winter hive wrap ($26.99), and put emergency feed directly above the cluster where a colony can reach it without traveling. The whole configuration is in the winterizing guide.

When the box still holds capped honey and the dead cluster is the size of a softball, the colony did not run out of food. It ran out of bees. Two causes dominate.

Queen failure in the fall. A colony that lost or superseded its queen in late summer, or whose queen simply stopped laying well, never reared an adequate generation of winter bees. The evidence: no brood at all in the fall inspection you may or may not have done, a very small population in October, sometimes a dead queen in the cluster, sometimes drone-laying patterns on old comb. The fix is a fall queen check as part of winter prep, and requeening on a schedule rather than after a failure; see the requeening guide.

Varroa-shortened winter bees. This is the more common answer and the more painful one, because it is invisible in October. Winter bees are reared once, around September, and mites feeding on those pupae while injecting deformed wing virus produce adults with a fraction of the intended lifespan. The colony looks fine at the last inspection, dwindles steadily through December, and is a fistful of bees by January, with honey untouched and very few mites left to find because the mites died with their hosts. That last detail traps people: a low mite count in a dead hive does not exonerate varroa. The mechanism, mites feeding on winter-bee pupae while vectoring viruses, is the one every major program organizes its advice around, including the Honey Bee Health Coalition's varroa management resources.

To distinguish them, look at the brood comb from last fall for mite frass and at the dead bees for deformed wings, and be honest about your monitoring records. If you did not count mites in August, varroa is the leading hypothesis by default. The mechanism is laid out in the virus guide and the timing in the varroa timing guide. Next season, the fix costs five minutes a month with a Mann Lake Varroa EasyCheck ($30.50).

A varroa collapse looks wrong in a specific way that is worth memorizing, because it is the most common cause of death in US hobby apiaries and it is routinely misfiled as starvation or "they just disappeared."

The population is missing rather than dead. A colony that had eight frames of bees in September leaves a small cluster and a surprisingly thin layer of dead bees on the board. Sick bees drift out and die away from the hive.

Stores remain. Frames of capped honey, sometimes most of the winter's supply, untouched.

Mite frass in the brood cells. Angle a fall brood frame into direct light and look at the upper cell walls for small white crystalline specks. That is mite waste, and it is direct evidence of reproduction under the cappings.

Deformed wings among the dead. Crumpled, stunted wings on bees in the cluster or on the board.

Spotty last brood. The final brood patch is scattered, with perforated and sunken cappings and larvae dead at various stages, which is parasitic mite syndrome and is the picture most often mistaken for foulbrood. It does not rope. If it ropes, go to the AFB guide immediately.

Actual mites visible on dead bees or in the debris, though their absence proves nothing.

The change this diagnosis demands is not a product. It is a calendar: monthly alcohol washes from spring, a treatment at 2 to 3 mites per 100 bees, an August or late-July knockdown before winter bees are reared, a verification recount, and fall counts to catch reinvasion.

Bees survive cold. They do not survive cold water dripping on them. A hive with poor ventilation condenses the cluster's own moisture on the underside of the lid and rains it back down, and a soaked cluster in January is finished.

The evidence: wet, matted dead bees, mold on comb, frames, and the bottom board, water staining down the inside walls, ice on the inner cover on the day you open it, and sometimes a slimy layer over the whole bottom board. Distinguish this from the mold that grows on any dead hive over several weeks of spring weather, which is normal and means little on its own; extension programs such as the University of Minnesota bee health program put ventilation and moisture control at the center of northern wintering advice for exactly this reason. Moisture as a cause of death is indicated when the wetness is in and around the cluster and the colony was otherwise adequately stocked.

The fixes are hardware and siting, and they are cheap relative to a colony. An upper vent or a notched inner cover gives humid air an exit. A quilt box absorbs moisture above the cluster. A wrap such as the MayBee winter hive wrap ($26.99) reduces the temperature differential that drives condensation and cuts wind load, with the standing caution that a wrapped hive still needs ventilation. Tilting the hive very slightly forward drains condensate out the entrance instead of onto the frames. The site itself matters as much as any of it, per the placement guide, and the whole configuration is in the winterizing guide.

Chewed, ragged cappings and a scatter of wax crumbs across the bottom board and landing area mean the hive was robbed out. The important question is whether that happened before or after the colony died, because the answers are opposite.

Robbing after death is the usual case and is not a cause of anything. A colony dies in December, warm days in February bring foragers from strong hives, and they strip the stores in a week. The signature is torn cappings and wax crumbs with a colony whose other evidence points elsewhere, plus stores that vanished later than the bees.

Robbing as a cause happens in late summer and fall dearth, not midwinter, and it kills weak colonies outright, often with dead bees showing fighting damage at the entrance and a colony emptied of stores in early autumn. If a colony was strong in July and empty in September, robbing belongs on the list, together with the mite reinvasion that robbing brings with it.

Prevention is entrance management: reducers and robbing screens during dearth and after any colony in the yard weakens, per the robbing screen guide. And the corollary for the yard: a dead hive full of honey left standing open is a robbing magnet and a disease vector, so close it up or break it down promptly.

Mice move into hives in the fall when the cluster contracts, chew out a cavity in the comb, and build a nest of grass and shredded wax, usually in a corner of the bottom box. They rarely kill a strong colony but they wreck frames and stress a weak one. The evidence is unmistakable and so is the smell. The fix is a mouse guard or a reduced entrance installed before cold weather, not after, and the broader predator picture is in the apiary predators guide.

Wax moths are the most misunderstood finding in any deadout. Silky webbing, tunnels through comb, and cocoons chewed into the woodenware look like the cause of death, and they almost never are. Wax moth larvae destroy comb that no colony is defending, so their presence means the colony was already dead or hopelessly weak. Blaming the moths is how a beekeeper avoids the actual diagnosis. See the wax moth guide for the full biology and the wax moth treatment guide for stored comb protection.

Small hive beetles can genuinely finish a weak colony, and in warm regions they can turn a deadout into a slimy, fermenting mess within days. Slimed frames smell of rotting oranges and are usually not worth saving. Details in the small hive beetle guide.

Ants, earwigs, and spiders in a dead hive are scavengers with no diagnostic meaning at all.

Brown or yellow streaking on the frames, the top bars, and the inside walls of a dead hive is common and gets over-read. Streaking is dysentery, which means the bees were confined too long without a cleansing flight, or were eating stores high in water and indigestible solids, such as fermented syrup or honeydew honey. It is a real finding about the colony's winter, and it is very rarely the primary cause of death.

It also is not a diagnosis of nosema, despite decades of beekeepers treating it that way. Nosema is a microsporidian parasite of the adult bee gut, it requires a microscope to confirm, and the species now dominant in much of the US frequently produces no streaking at all. The full separation is in the nosema and dysentery guide, including how to sample properly if you want a real answer.

What streaking should change: your fall feeding plan, so stores go in early enough to be ripened and capped; your moisture setup, so stores do not ferment in a wet hive; and your siting, so the colony gets morning sun and takes cleansing flights on marginal days.

Everything above assumes an ordinary deadout. One finding is not ordinary. If the brood comb has sunken, greasy, perforated cappings, if opening those cells reveals brown gluey remains with no bee shape left, if a toothpick ropes out a brown thread an inch long, if the frames carry a hot glue pot smell, or if there is hard dark scale glued to the lower cell walls that will not lift out, then stop.

Do not shake the frames out. Do not stack the boxes with your other equipment. Do not leave the hive open where it can be robbed. Do not offer the comb to a new beekeeper. Scorch or scrub your hive tool and change gloves before you open another colony, close the hive up, and call your state apiary inspector. American foulbrood is reportable in many US states, its spores stay viable in comb and woodenware for decades, and burning the infected combs is the standard resolution in most states. The complete protocol, including the rope test and what an inspection visit involves, is in the American foulbrood guide.

Most real deadouts are two rows of this table stacked: a varroa collapse that finished as a starvation, or a moisture problem that ended as a cluster isolation. Write down both, and change both.

Absent any AFB suspicion, a deadout leaves you the single most valuable asset in beekeeping: drawn comb. A colony given drawn comb builds faster, stores sooner, and is far more likely to make surplus honey in its first season than one starting on foundation, because drawing comb costs a colony an enormous amount of nectar and time. A package installed onto drawn comb in April is a different animal from one installed onto bare foundation.

Keep: clean drawn brood comb, capped honey frames, pollen frames, and all the woodenware. Frames of capped honey are next winter's insurance and next spring's feed.

Cull: comb that is black and heavy with cocoons, comb that is moldy through rather than surface dusted, comb slimed by hive beetles, comb crushed by mice, and any comb you cannot identify with confidence. Old brood comb was on the rotation list anyway; the frames go to the wax rendering guide and the wax is worth something.

Clean: scrape the boxes, bottom boards, and inner covers of propolis, dead bees, and mold. A stiff brush and a scraper will do it, and a light scorch of the interior is cheap insurance on any hive whose history you are unsure of. Mold on comb usually gets cleaned up by the next colony and is not a reason to discard an otherwise good frame.

Do not: feed honey frames from a colony with an unexplained disease picture to another colony, and do not give comb away to another beekeeper until you know what killed the hive.

The moment a colony stops defending comb, wax moths start looking for it. Larvae tunnel through comb eating wax, cocoon debris, and pollen, and a stack of unprotected brood frames in a warm shed can be ruined in a few weeks. Protecting salvaged comb is the last step of every deadout autopsy.

Freeze first. Twenty-four to forty-eight hours in a freezer kills wax moth eggs and larvae in the comb you are storing. This is the single most effective step and it costs nothing but freezer space.

Store cool, dry, and light. Wax moths hate cold, light, and airflow. Frames stored in a cold shed over a northern winter are effectively safe. Stacked boxes crisscrossed so air and light pass through, or frames stored in a well-lit space, do much better than a sealed dark stack.

Use a biological control per label. For long storage in warm regions, the standard tool is a Bacillus thuringiensis based product applied to comb. Certan B402 ($44.00) is the familiar option in this category, used exactly as its label directs on stored comb. Follow the label for dilution, application, and any restrictions; we publish no dosing here, and the label outranks this page.

Do not use household mothballs. Naphthalene mothballs are not a legal or safe treatment for beekeeping equipment, and they contaminate wax. If you use any registered fumigant product for stored comb, use only a product labeled for that purpose, exactly as its label directs.

Full options, tradeoffs, and the biology behind them are in the wax moth treatment guide and the wax moth guide.

Finish the autopsy in the notebook, not in your head. The entry that is worth writing looks like this: date, cluster size and position, stores remaining and where, mite evidence, moisture evidence, scavengers present, smell, and a one-sentence verdict. Then, underneath, the change: "count mites monthly starting in April and treat in the first week of August," or "add a quilt box and a wrap before Thanksgiving," or "check for a laying queen in the second week of September."

One change, executed, beats five resolutions. And there is a version of this that is worth saying plainly: national loss figures reported by the Bee Informed Partnership have run around 40 to 50 percent annually in recent years, so losing a colony puts you in the company of most beekeepers in the country, including the professionals. What is not normal, and what this page exists to prevent, is losing the same colony to the same cause three winters running because nobody read the frames.

Then get the equipment ready. Clean boxes, frozen and protected comb, and a plan for bees in spring, from the buying bees guide, from a split off your surviving colony per the splitting guide, or from a swarm you catch. Drawn comb and a diagnosis are a good position to start a season from, which is the most useful thing a dead hive can leave you.