Common Bee Diseases and How To Treat Them

[Note: Materials for this page are taken directly from the Queensland Department of Primary Industries and Fisheries Beekeeping Disease page. Please refer there for actual beekeeping information.]

European Foulbrood

European foulbrood (EFB) is a brood disease of honeybees caused by the bacterium Melissococcus pluton. The disease is endemic throughout Eastern Australia, but is not known to occur in Western Australia. Worker, drone and queen bee larvae are all susceptible to EFB infection. Larvae are most susceptible to infection when they are less than 48 hours old, and usually die while still in the coiled state. Poor nutrition and severe stress, for example insecticide poisoning, often cause this disease to break out.The larvae first turn yellow then brown in colour. In old larval remains, a secondary invading bacterium, Bacillus alvei is also commonly present. The disease is usually noticed in early spring, and to a lesser extent in autumn.

When EFB infection is light, treatment is usually not required as the disease often disappears during a good nectar flow. Requeening of the hive is also advocated as a treatment. Stress is also an important factor in the control of EFB. Stress can result from:

European foulbrood can be controlled with the antibiotic oxytetracycline hydrochloride, (also called oxytetracycline or oxytet). If measured dosages are fed to bee colonies in the prescribed manner, the drug will prove an invaluable tool in apiary management.

Sacbrood

Sacbrood is an infectious disease which affects the brood of honey bees. It mostly occurs as a mild infection which only kills a few larvae, but it can be more severe. Few hives die out as a direct result of sacbrood, but many are weakened to an extent where they succumb to other threats.

Sacbrood is an infection caused by a virus. Remains of larvae that have recently died are yellow in colour and are highly infectious. Larval remains more than two months old are brown and dry and are not infectious.

Requeening infected colonies is a recognised form of control. It is not practicable to requeen every colony which displays only a few larvae infected with sacbrood. However, once more than 5% of brood is infected, thought should be given to replacing the queen with one bred from a hive showing no sign of the disease. Combs with less than 20% of the brood infected should be removed from the brood chamber and placed in the honey super. Replace the combs with foundation if the bees are strong enough and conditions permit. Hives with mild infections should be checked every few weeks for any sign of the disease worsening.

Combs with more than 20% of brood infected should be removed from the hive and could be either melted down or placed in storage for two months. Combs in storage need to be protected from wax moth. A solar wax melter is a suitable device for melting down combs on a small scale. After removing old and known contaminated combs, the hive should be requeened, packed down and stimulated by feeding sugar syrup or moved to a honey flow.

Control measures will not ensure immediate removal of the problem from apiaries but, if brought into general management practice over a period of time, the sacbrood problem should be reduced. Antibiotic treatment will not control this disease.

Chalkbrood

Spores are highly infectious and are carried in contaminated pollen, by infected foraging bees leaving spores at floral and water sites, by queens, drifting bees, and drones. Shifting bees on trucks with open entrance causes drift and hence spread of disease. Spores remain viable for up to 15 years or more in equipment and soil. Use of contaminated sites and old equipment could lead to infections. Interchange of equipment by the beekeepers also spreads the disease.

There are three means by which the control of the disease has been attempted:

There is no effective chemical agent that is effective for use against the chalkbrood fungus therefore chemicals are not recommended for the treatment of chalkbrood in Australia. Management practices which reduce the stress on hives also reduces the number of chalkbrood spores. Maintaining strong healthy colonies has been demonstrated to reduce the effects of chalkbrood. Management practices which may reduce the effects of chalkbrood disease are: Good hygiene will also help. Change clothes and disinfect smokers, boots and hive tools using chlorine bleach between apiaries or infected hives.

Some hives are affected with chalkbrood more than others. Most of this variation in susceptibility is due to differences in the ability of bees to uncap and remove diseased brood. By selecting queen bees or obtaining queen bees from hives that show resistance to this disease, the effects of chalkbrood can be reduced.

A combination of management practices which reduces stress, reduces chalkbrood spores, maintains strong hives, and selects queen bees that show resistance to infection, are currently the main ways to minimise the effects of chalkbrood.

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