By : Ross Conrad
It’s March in the Northeast and for beekeepers that all too often means finding dead colonies in the beeyard. Winter losses for many beekeepers, especially in Vermont, are liable to be higher than normal this year given the dramatic increase in average mite loads that were found in many areas last season. However, mites are not the only thing that can kill a hive of bees. Are you well versed in identifying the clues left behind in dead hives to be able to tell with a relatively high degree of accuracy what killed those colonies?
Some causes of Winter hive loss are easy to determine even by the novice. When colonies are found knocked over and split apart, with half eaten combs and broken equipment scattered about the apiary, it is fairly easy to determine that a marauding bear is the culprit even if you don’t see bear tracks about. Most other causes of winter hive loss however, are more challenging to decipher and some can be practically impossible.
One of the more easily detectable signs of Winter colony loss is the presence of drone brood cells, either capped or recently uncapped, and many dead drones in spring, all of which suggests a failed queen. During the warm season when a queen fails and starts to become infertile, a colony will often successfully replace her through the process of supercedure. New queens raised during the cold Winter months however, are not able to go on mating flights. This condemns the colony to raising bees from only infertile eggs. Such a colony known as a “drone layer” is destined to dwindle and die as old workers die off and only young drones take their place. This is why ensuring that a relatively young and healthy fertile queen is heading up your colonies as they head into Winter is important.
Recent research has revealed that mites weaken a bee’s immune system by feeding on its fat bodies. This makes them much more susceptible to a host of viruses and diseases that are sometimes referred to as Parasitic Mite Syndrome. While the classic situation is the colony that goes into Winter with a high mite load and does not live long enough to see Spring, bees can also succumb to the mite during the warm active months. One scenario is the colony that emerges from Winter so weak that the small cluster of bees are unable to generate enough warmth to fend off a late season cold snap. The bees starve just inches away from capped honey in the hive, leaving a small dead cluster on the surface of the comb, with many bees head first in the cells looking for a last drop of honey to fuel the production of body heat in order to contribute to the cluster’s collective warmth.
Another example of Varroa related colony death is capped brood with pinholes in the capping’s, or pupae that is uncapped or only partially capped and looking unhealthy. This is often coupled with white flecks of mite feces left behind in empty brood cells where Varroa were reproducing. Other symptoms of Varroa induced colony loss are dead hives containing dead bees with deformed wings and/ or shrunken abdomens, and bottom boards covered with dead mites.
Sometimes a colony will starve as a result of going into Winter with insufficient food stores causing the bees to eat themselves into a corner where there is no honey. Bees are vulnerable to starving this way when significant amounts of empty comb or undrawn foundation are left in the hive in fall. Some would call this starvation, while others would blame beekeeper error. The colony that is found dead up against the inner cover in a Langstroth hive, or on the last comb(s) in the row of a top bar hive with no honey on any combs near the remains of the cluster and bees head first in the cells, also points to starvation as the primary cause of death. Or was it poor judgement on the part of the beekeeper? Preventing starvation in Winter is perhaps the easiest thing a beekeeper can do. It simply requires appropriate inspection in late-Summer/early Autumn and the effort to feed adequately before the cold weather sets in.
As mentioned above, the dead cluster inches away from honey stores with numerous bees head first inside the cells as they looked in vain for a last drop of honey in the comb is a classic find in northeast colonies that do not make it through the winter. Sure the ultimate fate of the bees in such a hive was starvation but, one could say it was the cold that actually killed the bees – or perhaps it was starvation because they were unable to access enough honey to generate heat. Or maybe since the small cluster couldn’t access enough honey due to diseases that reduced the size of colony’s population, the real culprit were pathogens. However, the initial cause of this chain of events was too many mites in the hive in Autumn. So what killed this colony? Some would say mites, others would blame the diseases, and still others will point to the cold or lack of honey. And in one sense or another, they all would be right. Sometimes things get complicated.
High moisture/Wet bees
When a colony is found dead and the combs and bees are moldy and damp, high moisture and insufficient ventilation is likely to blame for the moldy conditions. This situation may be caused by ventilation being cut off by winter wrapping, or by the closing down of the entrance with a mouse guard. Other times it can be something as simple as a hive cover that was not secure and blew off in strong winds allowing precipitation to enter through the hole in the inner cover. Bees can handle being wet in warm weather, but getting wet during the cold of winter is usually deadly, especially if the colony has already been weakened by something else.
American Foulbrood (AFB)
The classic signs of AFB: Perforated capping’s that may be dark brown or blackish and greasy in appearance; a shotgun brood pattern; the strong stench of foul brood disease; and a positive rope test should be competently administered and recognized by every beekeeper. The danger to the rest of the bees in the apiary, not to mention the rest of the colonies in the neighborhood, make this deadly and highly contagious bee disease enemy number one of all pathogens, and thus beekeeper identification of AFB needs to be a priority. If you doubt your abilities to identify AFB, contact a more experienced beekeeper or your state bee inspector to look over the dead hive and provide confirmation of the disease if it is suspected. In the mean time, seal this dead colony completely to avoid spreading the disease.
When you find a dead colony with no honey in it, one important question to ask is “Did the colony living in the hive eat it all and starve, or did the colony die allowing the honey left in the hive to get robbed out by other bees?” If the cells where honey was stored looks rough like the capping’s were ripped open in a hurry and the bottom board is littered with jagged pieces of beeswax capping’s, the hive was robbed out. In such cases, one must evaluate the remains of the cluster and brood nest in an effort to determine why the colony’s population dwindled to the point where it was unable to successfully defend itself from robbers, lost all its honey and starved. Was the colony a small nucor newly installed package, or was it an established colony that had some other issue? Other considerations when it comes to robbing include, how large was the entrance opening(s) and were there too many entrances? Robbing can often be reduced or even eliminated by the beekeeper that is observant and proactive.
Colony Collapse Disorder?
A dead colony with few to no dead bees left in the hive is a classic find in cases of CCD. However, a colony that absconds will have the same symptoms. Add to this the fact that CCD has yet to be clearly defined, and while there are a number of things associated with CCD (Varroa, pathogens, pesticides, poor nutrition) there is no definitive test for CCD, attributing colony loss to CCD is very difficult at best. This is partly why we don’t hear much about CCD anymore these days even though annual average colony losses still hover around the same level as they did during the height of the CCD phenomenon.
When combs in a dead hive are found partially, or entirely destroyed and covered with webbing and there are cocoons imbedded in the wooden parts of the hive, wax moths have been at work. As scavengers, the wax moth plays an important role in destroying old diseased combs so that the other bees in the neighborhood are less likely to contract any contagious diseases that may have killed the colony. The challenge with wax month damage is that it tends to destroy and cover up the clues and evidence you need to determine why the colony grew weak and died allowing the wax moths to gain the upper hand. This is another reason why it is a good idea to inspect hives on a regular basis and not let them go for too long between inspections. As with starvation, wax moth damage is a sign that the beekeeper has not kept on top of what is going on inside their hives.
Small Hive Beetles
Sometimes small hive beetles become so abundant in a colony that the hive goes queenless and fizzles out due to a lack of young workers to replace their aging sisters. The beekeeper finds fermented honey and slimed combs, perhaps with the SHB larvae crawling all over the place. Was this death caused by the small hive beetle or a lack of a queen, or something else that weakened the colony to the point that SHB could get a foothold?
Sometimes no matter how hard you try, it is simply not possible to figure out what killed a colony even with expensive laboratory testing. Many viruses and other pathogens such as Nosema ceranae that can infect a colony of bees fall into this category. Some proactive beekeepers however learn to identify nosema themselves by using a microscope. Others just have to accept that they either have to spend a significant amount of money for equipment or are going to have wait for USDA lab test results or, not know at all.
While accurately identifying the cause of hive loss is not always easy or possible, it is always worth the effort especially if one wants to continually improve their beekeeping skill. As part of this process, keeping a journal and maintaining good records of all hive visits and observations can go a long way to helping you understand what happened to your colonies. When we figure out what is causing our bees to die, we can take preventive steps to stem the losses. That’s how we become good beekeepers.
Ross Conrad is the author of Natural Beekeeping and will be teaching an organic beekeeping for beginner’s course May 18- 19 in Lincoln, Vermont. For information or to register call Ross at 802-349-4279 or email firstname.lastname@example.org.