Here is my 2cents . I keep 500 -1000 hives in Fla. for about 12 years .
I bought all my equip ment used. I had a lot of AFB  until I started
useing patties and the mites came along. The patties made sure  I had
timely application of terra. I think the mites kill all the wild bees so
this might help keep down reinfestation. I think we are exposed to AFB a
lot and if we are our only defence is med. I think we have to assume
that we have spores in our hives all the time. We also want to by queens
from a very good queen producer. I do not think that scorching your
boxes does much good because you are going to get exposed again shortly
unless you have got your bees trained not to rob. This is just some
things we need to think about. I have not had a problem with AFB and my
bees are exposed to more other hives in the spring than any where in the
world.
 
BUD