Oregon State Beekeepers Association

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Sudden late-spring colony loss by Dewey M. Caron

August 16, 2014

In mid-June there was a sudden loss of adult bees in several different apiaries in the Sandy/Estacada area of Clackamas County. In one instance the bees were in a top bar hive, in another a Warré hive and in the other two, bees were in Langstroth hives established on foundation from packages, and/or nuc purchases from different suppliers. The top bar hive was the only hive at the beekeepers residence but in the other 3 instances other hives in the same location did not have similar losses and in fact were doing OK.

Image: Colony with entrance block with dead adult bees

Losses were of the entire hive adult population or a significant portion (3/4ths or more) of the adults. Although the beekeepers intervened with feed once the loss was discovered (3-4 days after the discovery), surviving (most newly emerged) workers and their queen DID NOT RECOVER. Most dead bees were within the hive (not out front) piled on the bottom board blocking off the colony entrance. There were some dead bees on the inner cover and some bees were head-in in vacant cells. Matt Reed of Bee Thinking, Portland noted disoriented and convulsing bees when he looked at one loss incidence.

Other than the sudden loss, there were no commonalities discernable – beekeeper owners had different years of beekeeping experience, different hive types, different bee sources, there were expected differences in feeding when colonies were newly hived and the locations, while in the foothills, were not within the same forage diameter. The area has a number of nurseries but lots of open space, river bottoms and forage availability within sight at time of sudden loss.

I was asked by ODA pesticide investigator Isaac Stapleton to join him in a re-examination of the apiaries about a week later with concurrence of the hive owners. Joe Maresh, Portland Metro Association President joined us at one site. Our skills at autopsy of a dead bee hive are not very advanced. When looking to do a post-mortem autopsy of a dead bee hive, it is not always possible to conclude with certainty the reason for the sudden loss. I often say something like 95% likelihood of this cause or 75% one likely cause but 25% possibly for another alternative. I am making an "educated guess." The longer after an event the colony is examined, the less certain I can be about what might have happened.

In looking at a hive with a sudden change, I (like the beekeeper) was looking for "normal" and what about what is being viewed is abnormal — abnormal in what ways? I started with some assumptions as to why there might be a sudden loss of adult bees. In early spring, a colony loss is likely due to winter starvation (maybe actual death from a disease condition like BEE PMS). In the active season, a sudden loss is usually due to pesticide exposure, while later in the summer into the fall season, when resource conditions are poor, I first think robbing behavior. But there can be alternative explanations than the "expected" one — we all know bees can seemingly do the strangest things that defy the "normal" explanation.

Image: Joe Maresh opens a colony with dead bees. Media camera person looks on

Looking closely at two of the incidences, contrary to expected typical pesticide exposure loss, only some of the colonies (in apiaries with more than one colony) had the sudden loss, dead bees were within the colony, there were few dead bees head-first into cells, though many dead bees had their proboscis extended. Colonies showed dying brood with some new adults and, in one colony, a queen, though no eggs or young brood, was found. Stores of capped honey and cells of bee bread were noticeably absent. Some of the capped worker brood were still emerging but there was extensive dead brood. There was some brood disease present but not in any large quantity. The affected colonies were not being fed by their owners, normal for late spring in OR. Some sugar water had been fed, to at least the colonies in Langstroth hives, to help the colonies become established. All colonies, those with losses and those without any discernable loss, were actively building comb and all had quite prolific queens that were seeking to utilize every appropriate cell to lay eggs ( i.e pushing the workers to feed and care for a large amount of brood). ODA was called to investigate these incidences as a pesticide kill – the best "call" given time of year and the sudden heavy adult bee loss. Samples were taken of freshly killed bees. Analysis for 39 common pesticides, known to be hazardous to honey bees and likely to have been used in Oregon, was performed in the ODA pesticide testing lab in Portland. Laboratory analysis (ODA Press release August 11: Salem Statesman Journal August 12) reported "no detection of pesticides." Analysis by OSU Bee Lab for pests and diseases "found average levels of bee mites and Nosema disease." ODA pesticides program manager Dale Mitchell concluded "We're really left without any concrete evidence of what affected those particular hives."

Consulting other beekeepers with more experience in the Cascade foothills, including members of Portland Urban Beekeepers Association (PUB), Portland Metro Association and TVBA, I found that colony starvation, while not common, has been noted in some seasons. There is often a late spring dearth period after spring buildup in this region. The foothills have a micro-climate different from locations at lower elevations. Looking back at weather records, just before the first losses were noted, reveled several days where maximum temperature was only 60-62 F. at the nearest airport.

Image: Warre hive frame with a lot of brood but no food stores

I noted that in one apiary of 4 colonies in Langstroth hives, 2 had been given frames of honey at transfer from the cardboard nucs (all purchased from same supplier) and these two colonies had stores and needed supering. The two colonies not supplied honey had only partially drawn plastic foundation frames in 2 months. There were absolutely no stores present in these two colonies. I did not see evidence of robbing. The one colony with the sudden loss had a queen and newly emerged young adults 4 days after the loss event. When they were given a frame of honey, they did not quickly recover, as might be expected in a starvation situation. When a newly captured swarm was hived on the same equipment, it absconded within 4 days.

So the bottom line was a sudden loss of a significant number of adults, which in June usually means a pesticide loss. However hive examination showed enough non-typical symptoms to suggest that perhaps this was an unusual late spring starvation. What started as a 95% likely pesticide loss was now a 75% starvation "guess." In actuality we don't know what happened....and it looks like we never will — our autopsy skills are not very good when it comes to dead bee hives. Initially it appeared to be pesticide damage but it didn't quite fit. Closer examination appeared that it could be starvation but that too didn't quite fit.

Pesticide loss cannot be absolutely ruled out. Colony stress from rapid spring development, prolific queens, a late spring dearth period, along with need for extensive brood feeding and comb drawing meant a condition where colonies were living on the edge, needing a continuous inflow of nectar and pollen. While extensive, the ODA pesticide analysis did not include every possible chemical pesticide that bees might have been exposed to. Bees from colonies living on the edge might explore alternative forage and might be more at risk of pesticide exposure that bees from other colonies in the same apiary, with more ample stores, might not forage.

At least one media report reported (once testing for pesticides came back negative) that it was beekeeper error — specifically failure to adequately feed the colonies (Capital Press Aug 13). But that too is not valid because it too doesn't quite fit. Some of the colonies had been given some feed at establishment, though at the time of loss did not have feeders. There is no set standard of how much colonies should be fed and feeders on colonies this late into the spring usually are merely ignored by the bees in favor of flower resources. One dead colony had been fed until they stopped taking the syrup. Rapidly expanding colonies, with lots of brood and need for comb building, often have over-extended adult populations and unbalanced brood to adult population ratios.

Image: Beekeeper feeding a colony with a large number of dead bees. They did not recover.

To assume beekeeper error has another more insidious aspect. We WANT individuals to report these incidents — when unsubstantiated opinion comes to point the finger of blame on the individual reporting the incident, the message becomes garbled – do we SHUT UP and SUFFER in SILENCE or RISK being called part of the problem rather than a means to the solution. There were apparently at least two other individuals who had similar losses but did not wish to report or have them investigated.

One of the "reasons" commercial beekeepers elect NOT to report pesticide damage is they may lose their apiary site, a pollination contract, a farmer friend or when their dead colonies are looked at the beekeeper may be found in violation of some regulations/ordinance and end up suffering legal consequences — a double whammy — to go along with the loss of their bees. In fact the one individual beekeeper quoted in the story has received several very nasty, name-calling blog comments/email.

I don't know what happened — but I am not about to blame 4 individual beekeepers who all saw (and reported) the same thing — that it was their fault their bees died. Finally a postscript: I was involved back East in the initial investigations of BEE PMS (in early 2000’s) and with the national discussion that lead to initial elucidation of CCD. Neither what eventually came to be labelled PMS nor CCD fit the ‘expected’ loss pattern/symptoms. While these late-spring OR losses do not fit either BEE PMS or CCD, it seems a 50%-50% best guess pesticide damage or starvation. Could it, however, be something unusual and different?

Unfortunately we may never know, although we continue to look for a more complete definition.