Young pupae or recently sealed larvae are most susceptible. Infected larvae, stretched out in their cells in an upright position, are removed by nurse bees two to three days after symptoms first appear. In strong colonies, most of these mummies will be discarded by worker bees outside of the hive, thus reducing the possibility of reinfection from those that have died from the disease. Spores of the fungus are ingested with the larval food. At this stage, the larva is about six or seven days old.
Spores remain virulent for years.
Therefore, infected pieces of equipment, especially brood combs, are a reservoir for further infection. Chalkbrood usually does not destroy a colony. When the disease is serious, however, it can prevent normal population buildup and surplus honey production. Research has shown that the spores are easily passed from bee to bee. Therefore, drifting and robbing bees are potentiai vectors of the disease.