Sacbrood is a viral infection of the brood caused by Iflavirus genus and occurs when a diseased larva fails to pupate after they have been sealed in its cell. Fluid then accumulates between the body of the larva and the unshed skin, forming a sac. It is a relatively common disease during the first half of the brood-rearing season and can often exist unnoticed affecting only a small percentage of the brood and does not usually cause severe colony loss.
Initially during an infection, the virus particles replicate in the developing larva, which appear to develop normally until after being capped over. Typical symptoms include:
Chalkbrood is caused by the fungus Ascosphaera apis which is ingested by the larvae where it then penetrates the gut wall to absorb nutrients. As the spores germinate and multiply, the larva eventualy dies of starvation. After a few days of growth, the larva and fungus swells and fills the brood cell where it will eventually harden after a few days to it's distinctive 'mummyfied' appearance. Here it adopts a mottled white and black colour and each chalkbrood mummy will produce millions of infective spores which stick to the cells, hive components and adult bees.
Typical symptoms will start to appear in early spring as the colony starts to build up its population. Conditions such as damp and cold weather will promote fungal spores. Typical symptoms of chalkbrood will include:
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