Diseases of bees / Ministry of Agriculture and Fisheries.

Date:
1948
Catalogue details

Licence: Public Domain Mark

Credit: Diseases of bees / Ministry of Agriculture and Fisheries. Source: Wellcome Collection.

    13/36 (page 9)
    Cause. The condition is the result of some defect in the egg which does not become apparent until the larva has completed its development up to the pre- pupal or pupal stage. (Occasionally cases are reported in which the egg never matures and fails to hatch, but whether this phenomenon is an extreme form of the Addled Brood described here is not known.) The queen which lays the eggs is therefore to be regarded as the cause of the trouble. Symptoms. Both worker and drone brood may be affected. The brood normally dies in the pre-pupal or pupal stage, that is, after the cells have been sealed. Combs of sealed brood taken from diseased colonies often show a ‘‘ pepperbox ’’ appearance due to the patchy arrangement of the sealed cells. The dead pre-pupae are soft and moist, and are difficult to remove from their cells without damage. They are frequently greyish in appearance and of a rather shapeless sac-like form; or the head and thorax may already be visible, though somewhat shrivelled and contrasting with the lighter and broader abdominal parts. They shrink to form rather moist, slightly sticky, brown scales, but these are never so adherent as those of American Foul Brood. One of the outstanding features of the disease is that advanced pupae and bees apparently almost ready to emerge are found dead in their cells. In such cases the pupae are often of small size, with the abdominal parts much reduced in relation to the size of the head and thorax. The bees usually attempt to remove the dead brood by pulling off the cappings and chewing the cell contents. | Treatment. The queen should be destroyed and replaced with one which produces normal brood—preferably one reared in another colony, since daughter queens reared in the affected colony may lay eggs carrying the same defect as those laid by the parent queen. As the disease is not contagious and as the bees will gradually remove the dead brood from the cells, there is no need to destroy any of the combs, or to take any special precautions when manipulating affected colonies. The appearance of Addled Brood in several colonies in the same apiary would suggest that the queens are derived from a common stock, and that requeening with a different strain of bee would be advisable. SAC BROOD Cases of Sac Brood are reported occasionally in Great Britain, but there is some doubt as to whether the disease does actually occur here. It is believed to be caused by a virus. An infected larva becomes fully grown, but dies after its cell has been capped. It assumes a sac-like form with a tough skin, which is filled with a watery, granular fluid. The scale which forms later is loosely attached to the cell and is easily removable by the bees. No remedy for the disease has been found, but it seldom becomes serious and usually passes away without treatment. ABNORMAL CONDITIONS OF THE BROOD DUE TO FACTORS OTHER THAN DISEASE CHILLED BROOD This may be caused in a number of ways and is very often the result of carelessness or inexperience on the part of the bee-keeper. For example, hives may be opened too early in the spring, and the combs left exposed to a cold wind during the examination; or the brood may be “‘ spread ’’ prema- turely by the insertion of empty combs into the brood nest in the hope of stimulating the queen to increase her egg-laying.