Hi Liz,

I don't know of any way to resolve scab . If the spores are active, the weather is conducive and you have a plant that is susceptible to it you are pretty much sunk. My suggestion would be too ( as hard as this is) start over with trees that are not prone to this disease. Maybe take out one at a time so you still have at least one more mature tree while nurturing a younger one.

 The Plant Disease Pathologist out of Madison speaking about crabapple trees said that all varieties eventually become susceptible to scab. This is what he has noticed over his career. I would start thinking about another variety of tree.

I hope this helps,

Sally Granath

Hennepin County MG