Bee diseases & their control

MAAREC Publication 4.9
BEE DISEASES & THEIR CONTROL
Revised November 2005
This leaflet describes important symptoms, the trans- cells and also because the remains vary from the ropy mission and control of the three major brood diseases moist larvae in cells with dark sunken or perforated and the one important adult disease of honey bees.
capping to the dry scales lying in open cells whose The figures and portions of the text are taken from cappings have been chewed away completely by the material prepared by the United States Department Transmission: The spores are fed to young larvae by
DISEASES OF THE BROOD
the nurse bees. They then germinate in the gut of the Foulbrood, European Foulbrood and Sacbrood.
larva and multiply rapidly, causing the larva to diesoon after it has been sealed in its cell. By the time American Foulbrood
of death of the larva, the new spores have formed.
When the house bees clean out the cell containing Cause: Bacillus larvae, a microscopic spore-forming bac-
the dead larva, these spores are distributed through- out the hive and more and more larvae become in-fected. The honey in an infected colony becomes con- Effect: American foulbrood (AFB) is the most wide-
taminated with spores and can be a source of infec- spread and the most destructive of the brood dis-
tion for any bee that gains access to it. For example, eases. At first, the strength of an infected colony is
as a colony becomes weak, it cannot defend itself from not noticeably decreased and only a few dead larvae attacks by robber bees from strong nearby colonies; or pupae may be present. The disease may not de- these robbers take back the contaminated honey
velop to the critical stage when it seriously weakens to their own colony and start again the cycle of in-
and finally kills the colony until the following year,
fection and robbing. The beekeeper also may inadvert- or it may advance rapidly and seriously weaken or kill ently spread the disease by exposing contaminated honey to other bees or by interchange of infectedequipment. Using stored equipment contaminated by Symptoms: Death of an infected larva usually takes
spores will lead to a new infection even after years of place after the cell has been sealed and the cocoon
storage. Moreover, drifting bees or swarms issuing has been spun. First the capping of the diseased
from an infected colony may spread the disease.
cell becomes moist and darkens in color. Then as
the larva shrinks, the capping is drawn into the mouth
Control: Sanitation and elimination of disease res-
of the cell so the convex capping becomes concave.
ervoirs is a necessity for adequate control of Ameri- Worker bees may puncture this sunken capping and can foulbrood. The traditional control measure is to may eventually remove it altogether. At death, the dis- kill all bees in an affected colony and then destroy eased larva changes from a normal pearly white color bees and their comb by burning. The hive bodies, bot- to a creamy brown, then gradually darkens. These lar- tom board and covers can be salvaged by scraping thor- val remains can be drawn out into a brown thread or
oughly and then charring the inside portions and/or rope. As the larva dries up, it becomes dark brown.
The final state is a very dark brown, rather rough
scale that lies uniformly on the lower side of the
Ethylene oxide (ETO) combined with a drug treatment cell and extends from just below the mouth of the
has been found to effectively control AFB. ETO gas cell down to the base. These scales stick very tightly
must be administered under heat and pressure and to the cell and can be removed only with great
only a few states have facilities available for treat- difficulty. If death occurs at the pupal stage, the
ment with ETO. Contact the Apiary Inspection Ser- tongue of the pupa (false tongue) protrudes from the vice to determine what facilities are available in your scale across the cell. The odor of dead brood is very state. Maryland and Delaware have used an ETO cham- characteristic and has been described as resembling Drug treatment suppresses development of the AFB The overall appearance of a comb infected with Ameri- pathogen. However, treatment does not destroy spores.
can foulbrood is patchy (pattern referred to as “shot- Larger beekeepers regularly feed drugs as a prophy- gun”) because of the intermixed diseased and healthy lactic. The drug oxytetracycline (Terramycin) applied as a dust or in sugar syrup or as a grease patty is of American foulbrood (Paenibacillus larvae) in honey permitted in most states. No drug should be fed when bees. This drug is used only in cases of AFB that
there is danger of contaminating the honey crop. Fol- has been identified as resistant to Terramycin by
low the directions carefully and do not overdose. Re- the state apiary inspection service.
member that spores may and often do survive feedingof these drugs and colonies may break down with dis- European Foulbrood
Cause: Streptococcus pluton, a microscopic lancet-
Terramycin Soluble Powder is used for the prevention of European and American foulbrood. This product isavailable in a 6.4-oz packet. The package directions Effect: European foulbrood (EFB) is most common
can be confusing; to determine the correct application in the spring when brood rearing is at its height,
though usually the earliest reared brood is not af-fected. Sometimes the disease appears suddenly and • The legal dose is 200 mg, three times, at 4–5 day spreads rapidly within infected colonies; at other times it spreads slowly and does little damage. Euro- • One package contains 10 grams (10,000 mg) of pean foulbrood may severely weaken a colony but usu- ally does not kill an entire colony. As a rule, it sub-
• 10,000 mg ÷ 200 = 50 treatments per package.
sides by mid-summer, but occasionally it continues
• 50 treatments ÷ 3 = 17, so one 6.4-oz package treats to be active during summer and fall or may reappear in the fall. A good honey flow seems to hasten re-
covery.
The package calls for one teaspoon of TerramycinSoluble Powder per ounce of powdered sugar. Use the Symptoms: Larvae diseased by European foulbrood
move restlessly within their cells and, therefore, whenthey die, are usually twisted in the cells. However, • One level teaspoon of Terramycin = 200 mg, or one some larvae may be stretched out lengthwise from the top to the base. The larva collapses as though
• Each 6.4-oz package contains 50 treatments, so mix it had been melted, turns yellowish brown, and even-
one package with 50 oz (just over 3 lbs) of powdered tually dries to form a loosely attached brown scale.
sugar. Store in a tightly sealed container. (Expo- The consistency of recently dead larvae varies but it sure to air or moisture will break down Terramycin.) is not ropy. The odor of the larval remains also var-
• The dosage per colony is 2 tablespoons of this mix- ies but it is usually a sour odor. The scales are loose
ture, given three times, 4–5 days apart (for a total of within the cells and can be removed readily. Combs
600 mg per colony). Spread two tablespoons of the containing larvae infected with European foulbrood Terramycin mixture over the end of the top bars in usually present a rather uniform appearance because Preventative treatments can be applied to colonies in Transmission: The organism becomes mixed with the
the fall after honey supers are off and again in the brood food fed to the young larva by the nurse bees, spring 45 days before putting honey supers on.
multiplies rapidly within the gut of the larva, andcauses death within about 4 days after egg hatch.
House bees cleaning out the dead larvae from the cells distribute the organism throughout the hive. Since the honey of infected colonies and the beekeepers equipment are undoubtedly contaminated, subse-
quent spread of the disease is accomplished by
robber bees, exposure of contaminated honey be
Terra Brood Mix or Tetra Bee Mix. These products are the beekeeper, interchange of contaminated equip-
identical. This is premixed Terramycin and is used in ment among colonies, and perhaps to some extent,
the prevention of American and European Foulbrood.
by drifting bees. The bacteria is not a spore forming
It takes the guesswork out of how much Terramycin and sugar to mix together. For both products, the dos-age is 2 tablespoons, three times, 4–5 days apart.
Control: Requeening of badly infected colonies usu-
Spread the Terramycin mixture over the end of the top ally will help clear up the disease. Moving colonies to bars in the hive body with the most brood in it. Treat areas where there is a better honey flow or mix of colonies in the fall after honey supers are off and again flowering plants also usually decreases disease symp- in the spring at least 45 days before putting honey toms. Feeding of the drug oxytetracycline (Terramycin)
as a dust may be necessary in severe cases. Follow
directions for feeding terramycin under AFB.
The U.S. Food and Drug Administration (FDA) has ap-proved TYLAN (tylosin tartrate) Soluble for the control Sacbrood
extensive losses of adult bees. Workers with Nosemadisease have a life span shortened by 10 to 40%.
Cause: A virus.
There is reduced brood production in a colony affected
with the disease. It is also responsible for superse-
Effect: Sacbrood is a widely distributed disease, but
dure of queens especially in colonies established
it usually does not cause serious loss. However,
from infected package bees. Colonies infected with the beekeeper should learn to recognize sacbrood so Nosema have heavier winter losses and there is a it will not be mistaken for the serious foulbrood dis- decrease in foraging and colonies store less honey.
The decrease in honey production may approach 50%of production of healthy Nosema-free colonies. Sur- Sacbrood may appear at any time during the brood- veys of Delmarva apiaries have shown that better rearing season, but it is most common during the than 50% of all colonies can be expected to contain first half of the season. Usually it subsides after the Symptoms: No symptoms are specifically indica-
However, the beekeeper should learn to recognize tive of Nosema. Inability of bees to fly when they
sacbrood so it will not be mistaken for the serious leave the hive, excreta on combs or entrance boards, and a pile of dead bees on the ground in front of thehive may be manifestations of Nosema infection, but Sacbrood may appear at any time during the brood- they may also be caused by other abnormal condi- rearing season, but it is most common during the tions. Also, the disease may be present without any first half of the season. Usually it subsides after the obvious signs. however, if crawlers or unusual num- bers of dead bees are seen in the apiary or if a colonyfails to build up properly in the spring Nosema dis- Symptoms: Scattered among the healthy brood are
ease should be suspected. To definitely ascertain cells containing dead brood. Their cappings are dark
whether Nosema disease is present requires micro- and may be punctured or partly removed by the
scopic examination of the abdomens of older adult adult bees.
About the time the cell is sealed, the larva dies. When Transmission: The spores of Nosema apis enter the
it does, the head end turns up like the end of a
body of the adult bee through the mouth and germi- canoe and remains in that position; also the pearly
nate in the gut. After germination, the active phase white color begins to darken, and the skin then be- of the organism enters the digestive cells that line comes tough and the contents watery. At that stage, the midgut of the adult bee where they multiply rap- the larva, which resembles a liquid-filled sac, can
idly. The contents of these cells are used as a food be removed from the cell intact; hence, the name supply until reproduction ceases and new spores are sacbrood. The dead larva then continues to dry and formed. The cell then ruptures and sheds the new harden until the dried-down scale is almost black.
spores into the midgut where they pass down through The head end is usually the darkest. Scales of lar-
the small intestine to the rectum. Here these accu- vae dead of sacbrood can be removed from the
mulate and are voided in the excreta of the bee. The cell easily.
cycle begins over again when the spores contami-
nate the water or food of other bees. Spores will
Transmission: The virus is probably fed to the
remain viable for many months in dried spots of
young larva by the nurse bees in the brood food. It
excreta on brood combs. They lose their viability
multiplies rapidly within the larva until it causes within a few days in water exposed to direct sun- death. Then the house bees cleaning out the cells light, and they are also easily killed by heat and by probably distribute the virus to other larvae within the hive. The disease is usually limited to one or afew colonies in an apiary.
Near the end of winter combs are often soiled withexcreta dropped by infected workers. Other bees lap Control: No known control exists. In severe cases up the newly voided liquid excreta or become infected moving the colony or requeening may help. Colonies later when they pick up the spores in the dried ex- usually recover from sacbrood without beekeeper aid.
creta as they clean the soiled combs during the
spring expansion of the brood nest. Thus, at this
season, the disease within the colony increases
DISEASES OF THE ADULT
rapidly for a time, and a colony may dwindle in the
spring because of the premature death of overwin-
tered bees. Usually the colony survives and the pro-portion of infected bees begins to decline rapidly. This Cause: Nosema apis, a small, single-celled protozoan.
decline occurs because the excreta are normallyvoided away from the hive when regular flights be- Effect: Nosema disease is widespread and can cause
come possible in later spring. The infected bees no longer transmit the disease by excreta to the other Use drugs only in the recommended dosage to avoid occupants of the hive. Since the old bees now die off poisoning of bees and brood. ALL DRUGS ARE TOXIC
and are replaced by healthy bees emerging from the IF USED IN EXCESSIVE QUANTITIES.
brood combs the disease is not detectable in the
colony by the end of the season. However, enough
spores remain on the combs from the previous winter
Any drug used may become mixed into honey. DO NOT
to infect a few bees in the cluster that forms when ADMINISTER ANY DRUGS OR ANTIBIOTICS DUR-
winter sets in again. These infected bees then form ING A HONEY FLOW OR INTO HONEY SUPERS. The
the nucleus for a repetition of the cycle.
only time to feed medicinal agents is in the earlyspring during colony buildup or in the fall after honey The disappearance of the infection during the sum- mer seems to indicate that outside agencies such asdrinking water, flowers, or vegetation are not impor-tant in the spread of the disease. Also, the honey isprobably not contaminated to any significant degree,since excreta are not deposited on the combs whilethe cells are being filled and sealed. The spread ofNosema disease occurs chiefly because of the use ofcontaminated equipment, infected package bees, in-fected queens and her attendant workers, and therobbing of infected hives.
Control: The drug fumagillin (Fumidil-B) is approved
for Nosema control. It should be fed only in a sugar
syrup with feeding and mixing directions followed care-
fully. The recommended feedings is 100 mg. fumagil-
lin (about 1 teaspoon) to 1 gallon of sugar syrup (mix
2 parts sugar to 1 part water). Feed two or three gal-
lons in the fall and a minimum of one gallon to newly
installed spring packages. Spring syrup feeding would
be 1 part sugar to 1 part water. The drug will not com-
pletely eliminate Nosema since the disease spores
can survive drug treatment. Proper use of drug che-
motherapy has been shown to increase honey yields
by as much as 30 to 50 percent.
To eliminate disease spores from bee equipment,treatment in a heated chamber (1208F for 24 hours)has been found to be completely effective. EthyleneOxide (ETO) fumigation also eliminates Nosemaspores when combined with the heat treatment aswill acetic acid and heat. Treating equipment followedby treatment of bees with fumagillin is the best methodto reduce Nosema losses and promote colony health.
Precautions in Use of Drugs
Treating a colony with drugs does not destroy the dis-ease causing organisms but rather prevents themfrom multiplying. They also suppress outward mani-festations of the disease and disease can reappearafter cessation of chemical therapy. Therefore, USEDRUGS OR ANTIBIOTICS ONLY WHEN NECESSARY.
DRUGS SHOULD NEVER BE CONSIDERED A SUB-
STITUTE FOR GOOD BEEKEEPING. The beekeeper
should be able to recognize the various diseases and
treat colonies accordingly. The beekeeper should in-
spect every colony at least two times a year (spring &
fall) for disease.
COMPARATIVE SYMPTOMS OF BROOD DISEASES
Symptoms
American foulbrood
European foulbrood
Sacbrood
MAAREC, the Mid-Atlantic Apiculture Research and Extension Consortium, is an official activity of five land grant universities and the U.S. Department of Agriculture. The following are operatingmembers: Requests for information or publications should be sent to: MAAREC, 501 ASI Building, University Park, PA 16802 Phone: (814)865-1896 Fax: (814)865-3048 Web site: http://MAAREC.cas.psu.edu This publication is available in alternative media on request.
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Participants in MAAREC also include state beekeeper associations, and State Departments of Agriculture from Delaware, Maryland, New Jersey, Pennsylvania and West Virginia.
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