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American foulbrood
American foulbrood or AFB is by far the most virulent
brood disease known in honey bees. The reason for this
is the causative organism forms heat- and
drought-resistant spores, capable of germinating in a
favorable environment at any time. High incidences of
this disease in the past have led to the bee inspection
programs now present in most of the United States.
The disease is caused by the spore-forming bacterium,
Bacillus larvae. It attacks older larvae and young
pupae, which are literally digested by enzymes secreted
by the bacterium. Infected individuals turn brown, then
black, the resultant mass becoming a hard "scale" of
material deposited on the side of the cell.
The symptoms of American foulbrood include:
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A characteristic odor, sometimes described as sour
or "of a glue pot."
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Perforated or sunken cappings, darker in color than
healthy brood cappings.
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Resultant black scales, difficult to remove from the
cell because of their stickiness. The scales may
exhibit adult characteristics like legs, heads or
tongues, which are clearly diagnostical for this
particular disease.
Diagnosis of American foulbrood requires experience,
often only available from a trained bee inspector. The
"ropy" test can be used to make a preliminary diagnosis.
A stick or twig is inserted into the cell and then
withdrawn; the affected larvae "sticks" tenaciously and
the contents can be drawn out into a long string or
"rope." The Holst Milk Test another possible test. An
affected individual or scale is swirled in a weak
solution (1%) of skim milk. If the milk clears, American
foulbrood is suspected. Finally, a brood sample may be
sent for microscopic diagnosis to:
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Beneficial Insects Laboratory
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USDA/ARS
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Beltsville, Maryland 20105
Transmission of American foulbrood is possible in a
number of ways, including feeding infected honey and
pollen, using contaminated equipment, and installing
infected package bees or queens. Because honey from
unknown sources is always suspect, use of sugar syrup to
feed bees is preferable in almost all circumstances. It
is recommended that hands and hive tools be kept as
clean as possible at all times to avoid possible
contamination among colonies.
Because the spores can remain viable (capable of
germination) for so long, most states require bee
colonies with American foulbrood to be burned upon
discovery. Some, like Florida and Georgia, pay a small
indemnity, others do not.
Prevention of American foulbrood is accomplished by good
management procedures (this may include eliminating
colonies that are suspected of having the disease and/or
feeding an antibiotic). The only antibiotic legal to use
at present is oxytetracycline. Terramycin, a registered
trademark of Pfizer, Inc., is generally available at bee
supply houses.
A great deal of controversy exists concerning feeding
antibiotics to honey bee colonies for prevention of
American foulbrood. Most large-scale beekeepers find it
more efficient to routinely treat their bees. On the
other hand, many small-scale operators do not follow
such a feeding program, preferring instead to let
symptoms appear and then have the bee inspector diagnose
and then burn the colonies and collect the small
indemnity fee (not available in all states). This
removes disease reservoirs and eliminates susceptible
stock, not possible where preventative feeding with
antibiotics effectively may mask all symptoms. Generally
speaking, once a decision has been made to feed
antibiotics, such a prevention program must become a
permanent part of the operation's activities. Finally,
if antibiotics are not fed, this eliminates any risk
that they will contaminate a honey crop.
There is a general lack of agreement among researchers,
regulators and others concerning effectiveness of
preventative feeding as a desirable disease control
policy. Consequently recommendations may vary widely.
For a more detailed discussion on the matter, consult
appropriate sections in:
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Honey Bee Pests, Predators, and Diseases,
edited by Dr. R.A. Morse, Comstock Publishers,
Cornell University Press, 1978
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Honey Bee Pathology, by Leslie Bailey,
Academic Press, 1981, and/or
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The Hive and Honey Bee, Dadant and Sons,
Inc., Hamilton, IL 1975 (see references).
Most authorities agree that the approved dosage of
oxytetracycline hydrochloride is 200 milligrams per one
ounce feeding. Several formulations are presently
available and are named based on the amount of active
ingredient (i.e. TM-10 = 10 grams active ingredient per
pound). TM-25, simply called Terramycin Soluble Powder
(TSP), can be fed in syrup. The other formulation
(TM-10) is not soluble in water and must be fed as a
dust. At least one formulation of oxytetracycline
already mixed with a carrier can be purchased from bee
supply outlets.
The general rule to follow is feed according to the
instructions on the label. The label is the law and must
be followed to the letter. Unfortunately, the label is
often missing from small portions of the product and
confusion may result. According to the latest
information on the Pfizer label for (OXYTETRACYCLINE HCL)
Terramycin Soluble Powder #60-7000-00-1: Use 1 level
teaspoonful Terramycin Soluble Powder (TSP) per ounce of
powdered sugar per colony as a dust or 1 level
teaspoonful per 5 lb jar containing 1:1 sugar syrup per
colony. In addition, when making syrup it is advisable
to first dissolve the TSP in a small amount of water to
facilitate mixing. Because TSP is soluble, some have
experienced trouble using it as a dust formulation in
humid environments.
With reference to dusting, the label says to mix 1 lb
TM-10 (a different product from TSP) with two pounds of
powdered sugar, then apply one ounce of this mixture per
feeding. Applying the dust on the outer parts or ends of
the frames and feeding the syrup in pails is suggested.
Usually three feedings or applications (either syrup or
dust) at 4-5 day intervals are required in the spring
and/or fall at least 4 weeks before the main honey flow
to prevent contamination of marketable honey.
Remember: Laws governing agricultural chemicals
are continually in flux and new products are
periodically available which can make previous labels
and/or recommendations obsolete. It cannot be
overemphasized that only instructions as they appear on
the label should be followed when using any chemical
product either in disease and/or pest and predator
control.
European Foulbrood
European foulbrood or EFB is closely related to American
foulbrood in symptomology. However, the caustive
organism, the bacterium, Streptococcus pluton,
does not form spores, and so the disease is considered
less problematic than American foulbrood. The bacterium
generally only attacks younger larvae. As a consequence,
perforated cappings may be absent and the affected
individual may still be in a coiled state, resulting in
a "twisted" scale. As with American foulbrood, the EFB-infected
individual is reduced over time to a dark scale.
The symptoms of European foulbrood include:
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A characteristic odor.
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Perforated or sunken cappings, rarely present.
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A resultant black scale, often twisted or contorted
in its cell and easier to remove than American
foulbrood scales.
Diagnosis of European foulbrood is almost the same as
that for American foulbrood. The ropy test shows less
stringyness or ropyness (subjective at best and not
considered definitive diagnosis), and the Holst Milk
Test does not result in a clearing of the solution.
Again, the bee inspector's on-site diagnosis is
recommended, and samples may be sent to the Beneficial
Insects Laboratory.
Transmission of European foulbrood is the same as for
American foulbrood. Again, it is recommended hands and
hive tools be kept clean of debris (wax, propolis) when
working a number of colonies.
Treatment of European foulbrood is generally less
drastic than for American foulbrood. Only in very severe
cases is burning resorted to. Generally, requeening with
more resistant stock will clear up the disease. This
provides a break in the brood cycle and introduces new
genetic (possibly more resistant) material into the
colony. In addition, routine prophylactic with the
antibiotic oxytetracycline (Terramycin) is effective for
prevention of European as American foulbrood (see
section above on feeding antibiotics).
The amount of stress a colony is under can often be
correlated with development of European foulbrood.
Symptoms may appear when a large amount of brood is
being reared or during nectar dearth. The role played by
good management technique, therefore, which reduces
stress on a colony cannot be overemphasized in
controlling European foulbrood, as well as most other
diseases in bees.
Chalkbrood
Chalkbrood is a fungal disease. Although considered by
many to be a relatively minor disease of honey bees, it
appears to be on the rise in much of the United States,
and some geographic areas in Florida have reported large
infestations. The disease is characterized by infected
brood, called "mummies," which when removed from the
comb, appear to be solid clumps, reminiscent of chalk
pieces. The mummies can vary in color from white to dark
gray or black (when fruiting bodies are present).
It has been suggested importation of pollen from abroad
is correlated with the increase in incidence of
chalkbrood, a fungal disease. Growth of the caustive
organism, Ascosphaera apis, appears to be
enhanced by a number of factors, including high moisture
content (colonies not well ventilated in high humidity
situations), cool temperatures and colony stress.
There is no recommended chemical control for chalkbrood;
often requeening a colony will be effective treatment.
Good hygienic behavior by a colony, that is quick
removal of the mummies by workers, appears to aid in
clearing up the symptoms. Although it remains somewhat
of an enigma, some generalizations appear to be in order
concerning chalkbrood according to most authorities:
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It occurs mostly in colonies expanding during the
summer.
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It rarely kills a colony, but will weaken it,
leading to a reduction in honey surplus.
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It is promoted by certain conditions, dampness,
susceptibility of bee stock, inadequate nutrition,
other diseases or conditions (queenlessness, laying
workers, chilled brood).
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It is spread mainly by beekeepers.
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It appears that requeening with resistant bee stock
is the most likely way to clear up the symptoms.
For a fuller discussion of the disease, refer to
appropriate sections in the works referenced above.
L.A.F. Heath has also published more recent reviews.
See: "Development of Chalk Brood in a Honey Bee Colony:
A Review," Bee World, Vol. 63, No. 3, 1982, pp.
119-130 and "Chalk Brood Pathogens: A Review," Same
volume, pp. 130-135.
Stonebrood
Besides chalkbrood, another disease called stonebrood
has also been identified. This disease is presently of
minor importance, but should not be totally ignored by
bee inspectors and beekeepers. The causitive organism
may be one of several species of Aspergillis. As
with chalkbrood, no control has been developed.
Sacbrood
Sacbrood is a viral disease of the brood and considered
of only minor importance. Affected larvae appear to the
observer when removed from the cell to be a water-filled
sack, hence the disease's name. There is no recommended
control for sacbrood.
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