Hive Diseases: The Calcified Brood

Calcified brood is the most common of the mycoses infesting Apis Mellifera. This disease became very common in Italy during the 1980s, especially in northern Italy, probably in conjunction with the spread of Varroa, which weakened families considerably. It is caused by the ascomycete fungus Ascosphaera apis, which affects larvae, with an initial preference for male larvae. These are infected through the intake of food containing mycelium spores, which subsequently develop in the gut of the larvae, causing them to die after operculating the cell in which they are found. The best conditions for the development and spread of this fungus are low temperatures (optimum range of 22° to 30°) and high humidity. According to some studies, it would appear that dietary deficiencies (particularly of certain amino acids) may also contribute positively to the development of this disease.

The signs that allow this disease to be recognised are varied and easily recognisable. One of the first warning signs is to be found in the brood: a discontinuous and irregular brood is in itself an alarm bell. If one adds to this the discovery of larvae covered in a whitish substance that resembles mould on bread or the consistency of cotton, then the diagnosis becomes quite easy. This whitish substance then turns grey or black as the disease worsens, leading to the death of the larva and its subsequent mummification. The mummified larvae often appear whitish in colour, reminiscent of chalk, and with the remains of the head still black, curiously untouched by the fungus. It is from this characteristic appearance that the mycosis gets its name.

As the degree of infestation increases, and in the event that the bees have retained the tendency to keep the hive as clean as possible, all the mummified larvae that are ejected from the cells in an attempt to get rid of them can be found at the bottom of the hive and along the flight step. Another aspect to be taken into account is the state of the opercula. These may show small perforations (bees tend to uncapping cells containing infected larvae) or whitish spots scattered within the brood.

But what are the causes of this disease? As we have said, it is caused by a fungus that develops in the intestines of bees. Contamination occurs through feeding, when the larvae are fed food containing the spores. These, however, can also be spread as a result of looting incidents or through inspections themselves. If, in fact, a beekeeper inspects an infected family, he risks becoming a vector of contamination, spreading the fungus to other families through the use of material such as gloves or levers that have come into contact with the spores. This is an aspect not to be underestimated, as the spores can live up to 15 years, contaminating the entire hive, including combs, pollen and honey.

Obviously there are also family stress factors that contribute to the spread of calcified brood, creating favourable conditions for the development of the fungus and thus the disease. Certainly low internal hive temperatures (and in general any type of thermal shock) and high humidity levels are among the first causes, but there are also other aspects. A disproportion between brood and quantity of adult bees can be decisive in lowering the hive's internal temperature. If, in fact, the brood is larger than the number of adult bees, the entire nest will cool down faster, triggering the problems we saw earlier. Even small families run the risk of the same danger. One must therefore be very careful when these situations occur. In fact, the first infected larvae are generally found at the ends of the brood, where temperatures are lower or higher.

Moreover, an insufficient diet that generates nutritional deficiencies can make families susceptible to this type of disease. According to some studies, a protein deficit may favour the onset of calcified brood. Excessive movement of hives, the presence of other diseases and side effects of acaricide use can also weaken the family. Finally, a genetic predisposition must also be taken into account. Bees with a poor attitude to hygiene, inability to eliminate calcified brood before spores spread further, and a queen that does not lay as she should are not to be underestimated.

Once you realise that your household is affected by calcified brood, how should you proceed? If you think you can perform a treatment such as Varroa containment, you are very much mistaken. In fact, there is no drug or chemical treatment considered to be effective in combating this disease. This, however, does not mean being powerless in the face of the problem. In addition to the recommended preventive measures to avoid the onset of the disease, once it is detected, one must act promptly to avoid the spread of spores and to try to preserve the family. The normal behaviour of bees to combat this disease would be to eliminate the mummified larvae, which are left outside the hive, and to raise the internal brood temperature.

For this reason, the beekeeper can remove all larvae from the bottom of the hive and from the flight pod to prevent further spread of spores. He can also decontaminate all material, sanitising his equipment, the hive and replacing frames. In addition, it can move infected hives to dry and ventilated places. Practices that are not recommended, on the other hand, are all those that may contribute to a decrease in nest temperature, such as removing adult bees, adding brood and placing honeycombs at inappropriate times. Conversely, reducing the volume of the nest can encourage an increase in temperature and help the bees against the spread of this fungus. Changing the queen is also often recommended. In this way, the 'infected' one is replaced with a younger one belonging to a strain that is not susceptible to infection.

Keeping your bees constantly monitored is, therefore, very important to avoid and curb this kind of disease. High humidity is an alarm bell that should not be ignored. With 3Bee monitoring systems, equipped with specific sensors to be installed inside the hive, it is possible to keep not only the internal temperature but also the humidity under constant control. 3Bee Hive-Tech allows you to see immediately if there is a problem and to take prompt action. Discover all its features too..