I think if nothing gets rid of chalkbrood, then all colonies would show
symptoms. The bees themselves get rid of the disease. It must be the
hygienic behavior working. I've requeened lots of chalky colonies.
Sometimes it works, but not very often. Marla Spivack came to the
Vermont beekeepers meeting last weekend. She talked about hygienic bees.
They clean up a disease before it becomes infectious. Only about 10% of
colonies are hygienic. Maybe that explains why requeening only works
sometimes. Breeding is the way to go to get rid of chalkbrood. Why put
who knows what into your colonies as a Band-aid method.