Tag Archives: dead bees

Dead Colony Forensics by Dewey M. Caron

About a dozen brave individuals gathered at the Zenger apiary colonies Sunday April 15th, during a steady Oregon liquid “sunshine” rain for dead colony forensics with Dewey.  Photo right by Mandy Shaw.

Temperature was low 50’s, with only a couple foraging bees venturing forth from 4 of 8 colonies. We hefted boxes and did autopsy on two dead-outs.

Bees die overwinter for a number of reasons. By doing a dead colony autopsy we seek to determine what might have been the likely reason for non-survivorship.  Understanding the why might help us avoid a repeat this next winter.

The first dead-out we looked at (photo above) proved to be a tough diagnosis.

The colony was a mid-May nuc donation from Beetanical apiaries of Lane Co. Hive had a standard and a shallow. The shallow frames were quite full (>3/4ths of cells) with capped honey. The shallow was lifted off and placed on upside-down cover.  There were dead brood remains on three frames of the lower standard box plus a small (<2000) number of dead adult bees on the screen bottom board and outside the entrance. Two adjacent frames had widely scattered capped brood cells extending in an oval  covering over  1/3 of the middle of the frames; there was a fist-sized patch of compact capped brood but it was not contiguous with the scattered brood of the other two frames. There was no evidence of a dead cluster but a considerable number of cells of stored pollen on 5 frames. Ample mold was evident in pollen cells and as a powdery grayish mold on surface of cells. Colony was sampled for mites with a sugar roll in September and had only 2 mites (<1%).  It was NOT treated for mites as it was a non-treatment control. Colony was alive in a mid-October inspection.

Photo of the three frames with brood shows the frame with a patch of compact brood (held  in my right hand) and two frames with very scattered brood (one in my left hand and the third on top of adjacent hive; this frame is shown isolated in photo right). Full super on ground.   Photos by Deb Caron.

So what can we diagnose? Lots of honey and pollen stores so we can likely rules out starvation. Small number of dead bee bodies suggests a small colony but if we would believe death from a too-small population of adults, there should have been evidence of a cluster with bees within cells and dead bee remains on the frame(s).  There wasn’t.

Thus our best guess is a colony that had a BEE PMS condition. The scattered brood remains on both sides of the two frames suggests this –a spotty (snot) brood situation MIGHT have been diagnosed in the October examination, but this requires a close examination of the brood; we might have noticed evidence to too few adult bees to cover the brood – both are subtle clues. The fist-sized brood area,  one frame over from the other two frames with scattered brood, might have been bees trying to escape the high mite numbers and their unhealthy brood of the 2 frames with scattered cells. Adult bees were likely dying prematurely and abandoning their (unhealthy) hive, thus the reason we saw only a smallish number of adult dead bees. The colony likely failed to rear sufficient fat, fall bees. The colony probably died within a month after the last October inspection, probably from a virus epidemic related to the mite infestation. NOTE: The September mite sample is misleading/confusing (we would expect it to have been higher); if an additional sample was taken it would perhaps have been higher?

The second dead-out was a more standard necropsy. Hive was a spring split,that struggled all season. It had 2 shallows. Colony had a 19 mite count (6%+) in September and was treated with 2 formic pads between the two boxes. It was alive in March (this spring) but noted as small. It was fed dry sugar on paper (some still remaining) and provided with a frame of sugar candy.

Opening the top and removing moisture trap, (all Zenger hives had moisture quilt traps at top) showed a dead cluster of adult bees on 3 frames in top box at top of the box extending down about ½ way on the 3 frames (see photos; in photo right, hive tool is showing the remaining dry sugar on paper – quilt trap with wood shaving lower right). The adult bees were black and showed excessive moisture; there were many maggots (scavenger fly) feeding on the dead bees. There was capped brood in compact pattern within the cluster. Dead adult population was small (perhaps 8-10,000 bees). There was NO capped honey in any of the frames of either box. Lower box was empty. There were some dead bees on solid bottom board. There was little mold.

So what was diagnosis? The dead cluster is characteristic of a colony that overwintered the tough months (Dec-Feb) and moisture of adult bees, maggots and little mold suggests recent death. The compact brood shows the colony was starting to expand in the spring (flight was noted in March). Although dry sugar (as candy and crystal sugar) was given as emergency feed (hefting would have revealed lack of enough stores), it turned out to not be enough — colony likely starved. Bee cluster too small to generate enough heat to make slurry out of dry sugar or candy so bees couldn’t use it. Photo below shows one of three frames. We see “bee butts” under the dead cluster and compact capped brood.  Photo by Deb Caron.

All frames, except one with high number of drone cells, could be reused for anew colony installation (package, swarm, split). Brush off dead cluster and from bottom board. If inclined wash mold with bleach or vinegar solution.

Mold vs. drawn comb

Hives were very damp and moldy when I opened the dead hives. They were strong earlier with plenty of food packed away.

RESPONSE: When colonies die the combs do get moldy and honey (if any) will ferment and by the time we discover the loss the comb looks terrible. BUT give it to bees to clean up and you will be amazed how they will recover that comb. Drawn comb is our most valuable resource- don’t cut it out, nor throw it away.

Bee PMS

They died because I was gone for 5 months (Oct – Mar) Tried to feed them pollen/fondant while I was gone but it turned semi liquid ran into hive and one colony absconded and the other moved to one side and starved with honey in the hive (but not above them).

RESPONSE: Thanks for your comment on the PNW survey. Sounds like an instance of Bee PMS – so nothing would have helped. Running of feed does occur on occasion – but it was due largely to bees in poor health. The bees moving off brood area is very typical of Bee PMS.  I hope you have better luck this next time around.

Guest Blog “COMMON CAUSE OF WINTER DEATH IN NORTHERN CLIMATES”

COMMON CAUSE OF WINTER DEATH IN NORTHERN CLIMATES

HTTPS://BEEINFORMED.ORG/2016/03/08/WHY-DID-MY- HONEY-BEES-DIE/

By Meghan Milbrath, Michigan State University Extension, March 8, 2016

Guest Blog

Beekeepers in northern climates have already lost a lot of colonies this winter.  While official counts won’t be recorded for a few months, some trends are starting to emerge.  One of these trends is a specific type of colony death.  In Michigan, I’ve received so many calls describing the scenario below, that I can describe the deadout before opening the hive, or before the beekeeper describes it over the phone.  While I may impress some with these predictive powers, the frequency of these types of losses indicates a real epidemic that is affecting honey bee colonies in northern states.

Characteristics of the common early winter death in northern states:

1. The colony was big and looked healthy in the fall

2. A lot of honey is left in the top supers

3. The cluster is now small, maybe the size of a softball

4. There are hardly any bees on the bottom board

5. Near or just below the cluster is a patch of spotty brood – some fully capped, and some with bees dying on emergence (heads facing out, tongues sticking out).

6. If you look closely in the cells around the brood, you will see white crystals stuck to the cell walls, looking like someone sprinkled coarse salt in the brood nest.

AND

7. You don’t have records showing that varroa was under control.

Sound familiar?

We see this classic set of symptoms over and over in the states with a proper winter.   A big colony that seems to just shrink down and disappear.  Many people want to use the term colony collapse for this type of death, and while collapse is a good descriptor of what happens, this is not true colony collapse disorder.   This is death by varroa associated viruses.

How does it happen?

1. The big colonies –While beekeepers are often surprised that their big colonies are the ones that are gone first, it makes perfect sense in terms of varroa growth.  Since varroa mites reproduce in capped brood, the colonies that made the most brood (i.e. got the biggest) are the ones most at risk of having a high population of varroa.  Colonies that swarmed, or didn’t take off, or even fought a disease like chalk brood are less at risk from high varroa populations, because they didn’t consistently have large amounts    You should have good notes indicating cluster size going into winter, but even if you don’t, you can see the large circle of food eaten by a large cluster.

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This colony had a large brood nest (indicated by the dark comb in this frame from the top deep box), and a large cluster going into winter (indicated by the large amount of honey that is eaten away where the winter cluster started).  Varroa were never monitored or managed in this colony, and it was dead by February, if not sooner. (Photo by Meghan Milbrath)

2. Lots of Honey – Lots of honey means that the colony died fairly early. Colonies with high levels of varroa, they tend to die fairly early in the season (before February), leaving lots of honey behind.  Once the bees are stressed and in cluster, the viruses take their toll very quickly.  In some cases the colony will even abscond in fall, or be dead before winter really hits.

The colony shown above had a third deep box that was filled with capped honey, indicating that the bees died early, and starvation was not the culprit.

3. Small cluster – Varroa levels peak right when the winter bees are getting formed. The bees that emerge from varroa infested cells are weakened, and more importantly, are riddled with viruses.  Varroa mites are notorious for carrying deformed wing viruses (DWV), but are known to transmit many more.  When bees are close tight in a winter cluster, the viruses can spread very quickly.

In our colony, the cluster was only the size of our hand – some bees had their heads stuck in the cells, trying to stay warm, others had fallen between the frames.

4. No bees on the bottom board – When a colony starves, the bees just drop to the bottom board, and you end up with a pile of dead bees in the hive. When bees get sick with viruses and other pathogens, however, they often will fly away.   Sick bees by nature leave the colony to die in the field, an act designed to prevent pathogen transmission in the colony.  When most bees are sick, they either fly away, or are too weak to return after cleansing flights.  An early fall illness means that a lot of the bodies probably got removed by workers too.

The colony we examined had only a few bees left on the bottom board (1-2 cups).   We didn’t see a lot of varroa, but there had been some robbing, so wax cappings covered a lot of the board.

5. Patch of spotty brood/ Bees dying on emergence – When a colony succumbs to varroa associated viruses or parasitic mite syndrome (PMS), we see a lot of effects in the brood. Unlike American Foulbrood (AFB), which attacks the larvae at one particular stage, PMS will affect developing bees at many stages of development.  It is one of the only diseases where you see bees dying right as they emerge.

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Note the bee in the upper left is fully formed, and died on emergence.  You can often see frozen/melted larvae along with dead pupae.  Many beekeepers instantly suspect AFB, but AFB infected colonies usually will not be large and have produced a lot of honey going into the winter. (Photo by Meghan Milbrath)

6. White crystals in the brood – Around the cells where the brood died (the last place of the brood nest), you will often see white crystals stuck to the walls of the cells. These are dry (not suspended in liquid like crystalized honey), and are the crystalized pee of varroa.   Varroa mites defecate in the cells, and the resulting guanine crystals are left behind, and visible to the naked eye.

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Cells on the right hand side of this photo contain small crystals of guanine acid, indicating varroa defecation.   Notice the dry, irregular shape, and that they appear stuck to the walls on the cells.  Some cells on the left hand side of this photo contain crystalized sugar.  Note the wet/liquid appearance, and that it is largely in the bottom of the cell. (Photo by Meghan Milbrath)

7. No records that varroa was under control. Notice that this says ‘varroa was under control’, and not that ‘the colony was treated’.  You may have applied a treatment, but it may have been too little, or (more likely) too late.  This year was a particularly difficult year for this, because in Michigan we had a really late summer – it stayed warm enough for beekeepers to go into their hives well into October.   Many beekeepers took the extra time to put on a varroa treatment, thinking that they were lucky to get one in.  While that treatment could help the bees for next season, it was too late for this winter.  September and October treatments would have been applied after varroa had gotten to their winter bees.  Winter bees are born in the fall, and with their special fat deposits that allow them to live through the winter months, they are the one who carry the colony to the next season.  If the winter bees have already been infected with viruses, the damage is done.  No amount of treatment or varroa drop would bring the colony back.

The only way to know that you have varroa under control is to monitor using a sugar roll or an alcohol wash.  Just looking at the bees does not work; varroa mites are so sneaky, that you rarely ever see them, unless the infestation is out of control, and it is too late.   Many beekeepers say that they never see varroa in their hives, so they don’t think that they have a problem.   In fact, a varroa infested hive can actually look like it is thriving.

Underneath the lovely brood cappings, and away from our view, the mites are reproducing and biting the developing bees.  The colony can look fairly healthy until the mites reach a threshold, and the colony succumbs to disease.  By the time you see parasitic mite syndrome, or see varroa crawling on bees, it is often too late for that colony (especially if winter is just around the corner).   Getting on a schedule of monitoring and managing mites will give you peace of mind that your healthy looking colony is indeed healthy.

The silver lining

If the above scenario is familiar, don’t despair.   First, you are not alone.  Many beekeepers got caught off guard with varroa this year.  They didn’t realize how bad it was, or got thrown off by odd weather patterns.  Second, when the bees die, the varroa mites die too.   We don’t yet have evidence that the viruses would stay in the equipment, so you can reuse your old frames.  The honey that is left can be extracted to enjoy (if you didn’t feed or medicate), and frames of drawn comb can be given to new colonies.   Most importantly, if you recognize the above scenario in your colonies, you now have more knowledge as to what is harming your bees, and you can take positive action.   You have time for this season to develop a strategy. Monitor your varroa mite levels using a sugar roll kit (available at pollinators.msu.edu/mite-check/ or at Mann Lake), read about integrated pest management for varroa, and make a commitment to prevent high mite levels this year before your winter bees are developing.   This is going to be the year!

Meghan Milbrath, Ph.D.

mpi@msu.edu /517-884-9518

Meghan Milbrath is a beekeeper and the coordinator of the Michigan Pollinator Initiative at Michigan State University.   She performs pollinator related research and extension work, and works with beekeepers and stakeholders around the country. She started keeping bees over 20 years ago, and currently owns and manages a The Sand Hill apiaries, where she manages 150-200 colonies for queen rearing and nuc production

2015 Survey Q & A – Mite Problems

Q -In August I discovered severe mite problems in my 9 hives. I used powdered sugar and it seemed to generally improve the hives. I re-queened 5 hives. Those survived. The other 4 had a mite setback and died by late October. One hive had no bees. The others had dead adults. Two hives may have lost queens and I did not know it till it was too late.

A – Sorry to hear of your health issues. Mites can quickly overwhelm a colony and your discovery of a severe problem after not giving them as much attention as normal is not unfortunately, an unusual occurrence. I would have recommended a more ‘aggressive’ mite treatment than powdered sugar – powder sugaring is not very effective under the best of circumstances and seems to offer limited relief to the bees only under very low mite pressure.
Let’s hope this year is a better one for our bees and the mites do not get an upper hand over our management.

2015 Survey Q & A – No Active Hives (hiveyear calculation)

Q -The first page I did not have an option to put that I had 0 active hives. All mine died this year.

A – Thank you for sending a survey. We recognized too late that on this question zero was not accepted for a response yet the idea is to calculate the “hive years” for a beekeepers experience. We will be sure to find a new method for this and get it changed for next season. Thank you for sending the comment.

2015 Survey Q & A – Packages in late April

Q -Opinion on my failed colony: It never had a chance. Got the packages in late April; day received was nasty weather and by the time the second package was installed, they were extremely stressed with 100’s of dead bees on bottom of package. Honey flow was early and they just weren’t ready (the other package went in OK; the bees were mad because of the weather, but they weren’t dropping dead). Supplemental feeding in fall and winter didn’t save the 8-frame. Did same feedings for 10-frame and they thrived. I think my 8-frame simply died off. Found several hundred dead bees in the hive, but none were bottoms-up in the comb. On bottom board and scattered thru hive.

A – I would agree that the colony was likely started too late and they simply don’t have chance to grow enough and store enough to survive. Flows can be too early and thy use it to build bees and then lack stores. Feeding may or may not rescue a colony short on stores – we try and sometimes it still is not enough. It sounds like the 8 frame may have had queen event and that then lead to their doom. Thanks for sending a comment. Hopefully this season will turn out better.

2015 Survey Q & A – Backed my truck over them?

Q – Three of the hives that died displayed PMS symptoms, the fourth I dropped while moving it on a cold evening- it lived for a little while and then died.

A – You included a comment and appreciate it as it helps with our tally. My favorite on one survey was lost 5 colonies when I backed my truck over them. Dropping them is also a good “reason”. Thanks for sharing comment.

2015 Survey Q & A – Packages & Failed Colony

Q-Opinion on my failed colony: It never had a chance. Got the packages in late april; day received was nasty weather and by the time the second package was installed, they were extremely stressed with 100’s of dead bees on bottom of package. Honey flow was early and they just weren’t ready (the other package went in OK; the bees were mad because of the weather, but they weren’t dropping dead). Supplemental feeding in fall and winter didn’t save the 8-frame. Did same feedings for 10-frame and they thrived. I think my 8-frame simply died off. Found several hundred dead bees in the hive, but none were bottoms-up in the comb. On bottom board and scattered thru hive.

A – Thank you for sending a bee sample and for the additional details added under comments. Packages have a struggle to suvrive – late installations, poor weather and even feedings may not rescue them – better luck this season.