October 30, 2014

When Disaster Strikes

In late winter, beekeepers often find themselves thinking about their bees. Apprehension is most common when the previous fall had dismal honey production and when houses creak and snap on bone-chilling nights during January and February. Unfortunately, there isn’t much northern beekeepers can do during the dead of winter. At best, newspaper can be added on top of fiberboards of live hives that are completely saturated and candy boards given to populous hives that are low on stores. Both of these conditions are actually a good thing. This year, many New England beekeepers will find some of their hives cold and silent. After recovery from the dreaded feelings of failure and despair, the only thing to do is determine the cause of death via a postmortem.

There are a number of reasons that hives fail to survive the winter. Following are some common causes and conditions that beekeepers will encounter:

Starvation: Symptoms of starvation are easily distinguished by finding the cluster within a hive devoid of honey, or separated from honey stores that remain within the hive. Classic signs of starvation include a large cluster of dead frozen bees with the core bees headfirst in the comb. Frequently there is a patch of brood under the cluster.

Since the introduction of parasitic bee mites and Nosema ceranae, hives often starve with sufficient honey reserves since they have very small clusters. Essentially, these hives suffered a premature loss of adult bees in late fall and during the early part of winter and the cluster didn’t have a critical mass to generate heat and allow for movement. These colonies often have a small patch of brood within the cluster since bees will not abandon their brood in order to move onto honey. These small clusters are usually situated on the sunny side or warm side of the hive.

Tracheal mite: Colonies that succumb to tracheal mite (HTM) frequently exhibit abnormal behavior prior to death. Hives that have heavy infestations often break cluster on cold sunny days in February and March and cluster on the exterior sunny side of the colony. Symptoms of acute dysentery and/or Nosema are evident and a large number of bees are found on the bottom board or more frequently directly in front of the hive. The clusters of hives that perish from HTM are usually the size of a baseball or grapefruit and located on the outermost frames near the hive wall on the sunny side or hive’s front. A common trait of hives lost to HTM is an abundance of honey. Fortunately, unlike hives infected with American foulbrood, the honey and equipment are safe for feeding and restocking purposes with minimal cleanup. Therefore, block all entrances in these hives so other bees in the area don’t rob the honey when warm weather arrives.

Hive Lost to Nosema (photo: D. Israel)

Hive Lost to Nosema (photo: D. Israel)

Nosema: Hives lost to Nosema have symptoms of acute dysentery. Often there is excessive bee excrement on the inner cover, top bars and front of the hive near the entrance(s). There are usually a handful of bees remaining that appear bloated and wet.

Hives lost to Nosema ceranae often have a small cluster and a small patch of brood located directly under the top bar of the upper hive body. In northern climates there is associated dysentery and an absence of significant numbers of dead bees on the bottom board.

Varroa collapse: The symptoms of Varroa collapse vary somewhat according to treatment efficacy during the previous fall and pathogens associated with the mite infesta- tion. Small clusters are commonly found on the warm side of the hive with ample honey stores remaining. If the fall treatment was late or ineffectual, Varroa can be readily seen lodged between the ventral abdominal sclerites. Likewise, a number of bees with stunted abdomens and deformed wings are apparent. Upon examination of the lower hive body, combs with partially emerged bees (heads exposed with tongues extended) are visible. Upon removal, these bees often have stunted abdomens, deformed wings and mites within the cells. Hives that succumb to Varroa have very few bees remaining. If the fall treatment was effective, few mites are present and there are fewer bees with stunted abdomens and deformed wings. Again, the premature death of adult bees reduced the critical mass needed for thermoregulation in winter.

Queen issues: Failing queens and queenless colonies are a common reason for hive mortality over winter. Hives with queen problems are recognized by a disproportionate number of small drones (reared in worker comb) within the cluster. In addition, inspection of brood frames in the lower hive body and/or within the cluster will reveal drone pupal caps in worker comb.

Shrews: Evidence of shrew depredation is often first recognized upon removal of the outer cover. Broken bees are scattered on the inner cover (i.e. detached heads, abdomens and wings). The bee’s thoraces are absent since shrews eat these “meaty” appendages. Likewise, broken bees are found on the bottom board with shrew tunnels burrowed through the dismembered corpses. The combs of colonies killed by shrews are dam- aged and appear as if the wax and pollen was shaved off. The shrew will only chew the wax to the midrib (foundation) and not chew through the comb and make a nest like mice do. A musky odor is also common in hives lost to shrews, unlike the smell of urine associated with mice.

Other symptoms common among dead hives include: a sour smell caused by fermentation of uncapped honey and/or sugar syrup. Uncapped honey will absorb water from the air, thus diluting the honey, which initiates fermentation. It is important to initially shake the excess water from these frames, and again just prior to restocking the hive since water will again infiltrate these combs. In addition, hives with excess moisture (dead or alive) will frequently have a fluffy-white or blue-green mold on the outer frames and interior hive walls. These molds aren’t cause for concern and are often strains of penicillin.

What to do: In general, most hive equip- ment can and should be reused when the bees die, except when American foulbrood is the cause. In the case of starvation, the majority of frames need minimal attention except for those with excessive amounts
of dead bees stuck in the cells. Before temperatures warm and the dead bees begin to decompose, shake the bees off the combs and clean the bottom board, etc. Sometimes a majority of bees can be shaken out of the cells or removed with a shop vac. Some bee- keepers give combs with excessive dead bees to strong hives in spring so the bees can remove the corpses. A better strategy would be to cull the combs filled with dead bees and insert new foundation. Plastic frames can be scraped to the midrib and given back to hives. Frames with only a few bees stuck in the cells need no action and should be reused since bees can easily remove the dried corpses. Frames that have wet, mushy, decomposing corpses should be culled since fly maggots and hive beetles infest them— culling makes life easier for the bees.

Hives lost to queen issues need minimal action and should be treated as above. If there are brood combs with exces- sive drone comb, they should be culled. Likewise, combs with exces- sive shrew damage need replacement since the bees will likely rebuild the dam- aged comb with drone cells. Frames with minimal shrew damage can be reused.

Regarding Nosema, scrape and clean the woodenware and cull frames with exces- sive feces running down the comb. For minimally stained frames, scrape the top bars. The cappings on frames of honey can be cleaned by gently wiping the feces off with a cloth dipped in a bleach solution (1 bleach : 9 water). Warm water works well and gloves are recommended. Heat or acetic acid fumigation are the standards for killing Nosema spores when treating large amounts of equipment. Consult beekeeping textbooks for specifics.
Hives lost to Varroa over the winter can be successfully restocked. Unfortunately, recommendation for restocking equipment that has undergone colony collapse isn’t clear-cut in light of some CCD reports. A common concern about restocking this equipment pertains to the stability and virulence of virus particles within the equipment.

A number of commercial beekeepers state that the equipment needs to “rest,” vacant of bees prior to restocking. The question is, for how long and under what conditions?

In 2008, I successfully restocked equipment that had succumbed to parasitic mite syn- drome (PMS) brood, deformed wing virus infection of bees and brood, and Nosema the previous season. I must admit that frames with excessive amounts of dead brood were culled and replaced with foun- dation. Likewise, frames that had bee excre- ment running down the comb were culled. Only the newer and best looking frames of comb, honey and pollen were restocked.

Good news! Punxsutawney Phil did not see his shadow on Ground Hog day. Therefore, spring will arrive early and you will soon hear the birds chirping.

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