APIS Volume 2, Number 6, June, 1984
In this issue
- Stress --Disease Relationships
STRESS AND DISEASE RELATIONSHIPS
Reports from the citrus area vary considerably; the flow was spotty, with some beekeepers making a surplus, though not as much as "normal" years, while others say the bees didn't put up a drop. Colonies appeared to be in pretty good shape going into the flow. Populations were increasing and brood rearing was in full swing. The same conditions were apparent for the gallberry area; bees were in excellent condition, but cool nights apparently slowed the nectar flow.
All this boils down to a lot of stress. Colonies rearing brood are always under stress, but when a nectar flow doesn't come up to "expectations," the stress is magnified and can lead to a number of unpleasant results. One to come to my attention was a rise in incidence of chalkbrood. Some reports indicated as much as thirty percent of the colonies were removing mummies.
There still isn't much information on what to do about chalkbrood; paradoxically, the reports indicated populations remained high, even though some bottom boards were covered with mummies. Actually, this may be a good sign; it shows the bees were cleaning out the fungus infection as it developed. Good hygenic behavior like this is considered desireable in bee stocks, to keep disease to a minimum. Although it remains an enigma, some generalizations are in order concerning chalkbrood. Notice how many are correlated to stressful conditions (e.g. brood rearing, nutritional imbalance).
- It occurs mostly in colonies expanding during the summer (spring in Florida).
- It rarely kills a colony, but will weaken it, leading to a reduction in honey surplus.
- It is promoted by certain conditions, dampness, susceptibility of bee stock, inadequate nutrition, other diseases or conditions (queenlessness, laying workers, chilled brood).
- It is spread mainly by beekeepers.
- It appears that requeening with resistant bee stock is the most likely way to clear up the symptoms.
Chalkbrood is not the only stress-related phenomenon in beekeeping. Other diseases are high on the list. Nosema is a classic example. And if both nosema and chalkbrood increase during a period of stress, the effects on a colony could be devastating. A colleague also informs me that this same reasonining can be applied to Mexico, where recently the acarine mite has been introduced. Symptoms of acarine itself are mild when compared to those in a colony which has high levels of nosema and acarine together. There's a great deal of evidence to suggest that European foulbrood and a number of adult viruses also increase proportionally to the stress on a bee colony.
I've also had reports that population buildup seemed slow in citrus groves this year and last. Beekeepers' observations have resulted in a number of hypotheses for this, ranging from chalkbrood to pesticide application. At one meeting a specific substance, the pesticide Temik®, was implicated. The nature of these kinds of observations always needs to be critically examined; specifics are extremely important, without them diagnosis is practically impossible. All too often inadequate documentation results in generalizations that confuse the issue, rather than clarifying it. Thes circumstances may lead beekeepers and scientists alike into the trap of concluding that some single answer exists to what are usually extremely complex problems.
Perhaps the best example of this was talk a few years back about a phenomenon called, "disappearing disease." A number of beekeepers reported large losses of worker bees from their colonies for no apparent reason. This resulted in widespread concurrence from others. The phenomenon appeared to be the result of some hitherto unknown condition. For lack of a better term, "disappearing disease" was coined.
Dr. Hachiro Shimanuki in his treatise, "Synonymy in Bee Diseases," in Honey Bee Pests, Predators, and Diseases, edited by Dr. Roger Morse, Comstock Publishing Associates, 1978, said this so-called disease was, "...a classic example of a misnomer. In the first place the bees disappear, not the disease, and in my opinion, the term is used as an umbrella for what may well be many maladies." Indeed subsequent extensive research failed to isolate any disease organism in stocks that exhibited the condition. The symptoms are similar to other conditions like "autumn collapse," or "spring dwindling," which appear to be the result of stress related to nutritional imbalance. Subsequent research by Drs. J. Kulincevic and W. Rothenbuhler at The Ohio State University has revealed that expeller-processed soybean flour, long used to feed bees, may have been the culprit in some instances.
Another possible reason for slow population buildup in citrus groves may be just coming into focus. According to Dr. Randolph McCoy, University of Florida Agricultural Research and Education Center, Ft. Lauderdale, Florida, certain worm-like organisms called spiroplasmas have been found in flowers which are related to those implicated in a condition called "May disease," in France. Again according to Dr. Shimanuki, "May disease" previously has implicated pollen of buttercups (Ranunculus species), and has had many names, including running about illness, running-in-the-sand sickness, frenzy sickness, wing paralysis, trembling sickness, flight incapacity, paralyis, and reeling sickness.
A point too often neglected by those diagnosing beekeeping maladies is the genetic makeup of a colony. Some lines of bees are inherently more healthy and productive in specific geographic regions than others. This is the reason a universal recommendation given for practically any abnormal condition seen is requeening. Changing the queen often clears up a condition because there exists a great genetic variability of honey bee stocks in this country. This large variability means that a little selection by the beekeeper may go a long way in improving his/her bees.
Unfortunately, genetic analysis and control in honey bees is in its infancy, and few breeding programs provide the customer any pedigree data. Lacking such information, each beekeeper must become adept at observing his/her own and other's stocks with respect to disease resistance, productivity and ability to cope with stress. If this is not possible, then using several stocks or lines of bees and always culling out those queens whose colonies don't measure up to the beekeeper's standards is probably the best advice available.
It is a myth that better bee stock must always exist elsewhere. This has and continues to result in the widespread distribution of bee stocks worldwide. Recently, introduction of the Varroa and acarine mite, as well as the Africanized honey bee, has shown this practice to be fraught with error. In addition, other kinds of diseases extremely difficult to detect (e.g. viruses) may be introduced into bee populations. The United States has a law against importation of semen, eggs, brood or adult bees, and it is becoming more and more clear that this practice should be stopped and genetic selection of stocks in specific geographic areas be substituted, if more desireable strains of bees are to become available.
All this is not to make an already complex subject less understandable. Rather it is to plead for more concise observation and clearer thinking when developing conclusions and/or contemplating solutions to decline in colony productivity, and to always consider the role stree might play in certain situations. The successful beekeeper is the one who knows when to let the bees alone, yet actively manages and helps them through stressful times to attain their maximum productivity.
Sincerely,
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (352) 392-1801, Ext. 143 FAX: (352)-392-0190
http://www.ifas.ufl.edu/~entweb/apis/apis.htm
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
©1984 M.T. Sanford "All Rights Reserved
