A Practical Manual of Beekeeping by David Cramp

Author:David Cramp
Language: eng
Format: mobi
ISBN: 1905862237
Publisher: How to Books Ltd
Published: 2008-01-02T00:00:00+00:00

CO N T R O L L I N G D I S E A S E S A N D P E S T S | 187

is high. Most beekeepers don’t notice it mainly because it affects a small percentage of larvae only. Adult bees detect and remove infected larvae very quickly and so, if the beekeeper does notice the problem, this is usually because it has progressed to a stage where the workers can no longer control it. Therefore, by the time the beekeeper observes the symptoms, the disease may be too severe for the adult worker population to handle.

Both worker and drone larvae are affected. Pupae may be killed occasionally, but adult bees are immune to it. Dead brood is often scattered among healthy brood. Nurse bees are suspected of transmitting the disease by carrying the virus from cell to cell. It is also believed that robber bees spread the disease by taking contaminated honey from one colony to another. The spread of this disease is another reason why drifting and robbing should be prevented.

Fig. 26. Sacbrood larvae: typical position

Identifying sacbrood

The following are the signs of a sacbrood infestation:

„If the cells have been capped, the cappings may be perforated (if so, also check for AFB/EFB).

„If the cells are open, identification is easier. The larva’s head, the first part of the body to change colour, becomes dark brown to black. If lifted from the cell, the

abdomen is bloated, resembling a watery sack.

„Death usually occurs after the cell is sealed and the larva has spun its cocoon.

188 | A P R AC T I C A L M A N UA L O F B E E K E E P I N G

„The larvae die in an upright position in the cell, and this is very noticeable (see Figure 26).

„The larva eventually dries to a scale resembling a Chinese slipper or gondola. This does not adhere tightly to the cell wall and so, unlike AFB scales, the workers can remove them. By doing this, however, they tend to spread the virus throughout the hive.

„After a few weeks the larval remains are no longer infective.

Treating of sacbrood

Strong colonies and regular re-queening seem to be the best means of combating this disease – no antibiotic is effective at preventing or controlling it. Colonies suffering from this virus usually recover spontaneously when the honey flow starts because, at this time, there are fewer adults in the hive to pass on the disease.

Chalkbrood

Chalkbrood is a disease caused by the fungus, Ascosphaera apis, and it affects unsealed and sealed brood. It can be triggered by a change in brood-nest temperature. When there are insufficient nurse bees to cope with extreme weather conditions (e.g. for cold clustering and heat fanning), the brood may be left unattended. The first larvae affected are usually those around the edges of the brood, where the brood temperature may be higher or lower.

Stress of any kind can result in chalkbrood: high or low temperatures, wet or dry conditions, an increase in CO2, poor nutrition, a failing queen, poor hive management and moving hives.

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