Bees for Development Journal 127 June 2018
Control of Chalkbrood in Vietnam Nguyen Quang Tan Photos © Nguyen Quang Tan
Chalkbrood disease has been known for many years by beekeepers with Apis mellifera in Australia, Europe, USA, and many Asian countries. It is caused by the fungi Ascosphera apis and Ascosphera alvei. The disease occurs when the larvae ingest the fungal spores with their food. Once digested, the spores develop inside the larvae’s guts and absorb the nutrients. Ultimately, the larvae die of starvation and form white or grey, chalk-like ‘mummies’ which give the name of the disease. The fungi reproduce by spores which can survive for up to 15 years. Each mummy can create millions of spores which stick to the adult bees, combs, frames, hives and pollen. The chalkbrood mummies are easily visible in the cells. It is not unusual for worker bees to remove and deposit them on the hive floor or at the entrance of the hive. Only in recent years has the disease been seen in Vietnam. It causes significant damage to the beekeeping industry: colonies are weakening, honey yields decreasing and production costs rising. Chalkbrood in Vietnam We recorded the following epidemic characteristics of the disease in Vietnam: Infested honey bee species: There has been no recorded report of the disease in colonies of the Asian honey bee, Apis cerana.
The author checking a colony for symptoms of Chalkbrood
Condition of the infested colonies: The disease usually occurs in weak colonies of Apis mellifera with a lack of food and/or a scattered brood pattern.
pollen is commonly traded among Vietnamese beekeepers. Level of disease spread: Chalkbrood has spread more rapidly than diseases caused by the mites Varroa sp and Tropilaelaps clareae. However, it is spread more slowly than Sacbrood, a viral disease which broke out in our Apis mellifera colonies about ten years ago.
Age of the infested brood: The disease is mainly in the older larvae (4-6 days old) and prepupae (young sealed brood). Time of outbreaks: The disease usually happens and causes losses in the rainy season when the atmosphere is very humid.
Level of damage to beekeeping: This depends on the percentage of infested colonies and the situation of the diseased colonies, but in general Chalkbrood has caused severe economic losses for commercial Apis mellifera beekeepers.
Spread of disease: This can be from one colony to another, from one apiary to another, or from one region to another by foraging and robbing bees, and by beekeepers: bee transport, exchange of combs and/or other equipment. Noticeably, the disease can be spread quickly and far by bees fed by the beekeeper with dried pollen collected from diseased colonies - unluckily dried
Controlling Chalkbrood After some years suffering from the effects of this new disease, beekeepers have gained experience in its control, and the beekeeping industry in Vietnam is now recovering. Our experiences are: 7
