Hopi crabapple and my favorite-- Dolgo crabapple are somewhat cedar rust
resistant.

Yes, but they are very susceptible to other diseases. Suggest you contact your
local ag. extension agent for a list of crabapple cultivars suitable for your
area.
Apple scab is a particular scourge in Central NY. 'Dolgo' is terrible. When we
moved in, I cut down a sorry looking specimen and planted 'Camelot', one of the
newer dwarf cultivars. It hasn't blinked since. I have to spray my bonsai in
the Rosaceae (hawthorn, etc.) for rust occasionally, but it is not a big deal.

Another resolution I have made is to forever give up on trying to coax along
plants in a soil pH that is inadequate for them. For 4 years now I have tried
to coax along pinenut species. No more for it seems to be a waste of time and
energy.

How do you know that the problem is soil pH? Are you sure it is hardy where you
are?

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)