Zone 8 Georgia is very different from my dry zone 6/7 climate, so I'm not sure if I'm qualified to give advice.
Austin roses are offering L.D. Braithwaite as a standard.
http://www.davidaustinroses.co...
That rose grows beautifully here in our heat as a regular shrub rose, and I have not noticed any blackspot on the few weeks where humidity is high.
Can't comment on tree roses because I don't have a area sheltered from wind where I can place them!
Hopefully someone from the south will chime in!
