Disease-Resistance

A.T. "Buddy" Harrelson of Louisiana writes in the 1984 American Rose Annual:

      By the way, I don't believe healthy plants resist diseases or insects.  In fact, it would seem to me that bugs would thrive better on healthy plants.  I can imagine one bug signaling to another. . ."Hey!  C'mon over here!  The Chlorophyll is fine."  However, a healthy plant will recover more quickly should it sustain damage.  

This makes sense to me, including bugs' preference for good-looking plants.  I also agree with Buddy that healthy bushes recover more quickly from whatever attacks them than do their sickly cousins.

Some rose experts believe, however, that susceptibility to mildew can be predicted by how the foliage looks.  Leathery, glossy leaves, proponents claim, are less prone to mildew than dull, soft ones.  When I first heard this theory, I pooh-poohed it.  Now I'm not so sure.

If you asked me quickly to name a rose that mildews, I'd say Garden Party, definitely a rose with dull foliage.  We keep Garden Party at Garden Valley Ranch as a "standard" for mildew.  If the albino fungus is anywhere insight, it will find Garden Party.

If I were asked to name a rose that doesn't mildew, Cathedral comes to mind.  It has particularly glossy, leathery foliage.  There may well be something to this theory of foliage clues, and I intend to experiment with it.  In the meantime, I suggest that you check locally to learn how disease-resistance manifests itself.