After Tim Tompkins got finished preaching to us about proper selection
techniques that would rule out most if not all of the roses I want to
grow here in the swamps, he said:


Note that the scientific name of most of the fungal diseases include the
word 'rosa' in some form. These diseases are specific to roses and are not
transmitted from non-rose plants or trees.

This is hairsplitting of the highest degree. The same mold or other
fungus spores that cause downy mildew on peach trees causes downy
mildew on rose plants. Once on the rose plant, it gets the "rosae"
tag, Latin for "of rose" simply because in that particular case it is
ON A ROSE PLANT.

As for black spot, the fungus Diplocarpon rosae causes black spot in
roses.

The fungus Diplocarpon earliana causes a similar disease in
strawberries. Here is a site that discusses it:

http://www.inra.fr/Internet/Produits...ne/6dipear.htm

Diplocarpon mespili causes leaf spots in hawthorne trees that result
in defoliation. While the disease is referred to as Hawthorn Leaf
Blight, its action is the same as that of diplocaron in roses. Here is
the Cornell site that discusses this:

http://plantclinic.cornell.edu/FactS.../hawblight.htm

Therefore, while one may certainly say that apple trees do not get
black spot, one may not say that the fungus causing the disease is
specific to ROSES.

Here is one link that demonstrates that apple and peach trees are
subject to thesome of the same fungal diseases as roses.

http://www.ca.uky.edu/agcollege/plan...n/homefung.htm

Here is another that describes fungal diseases roses and fruit trees
sha

http://pearl.agcomm.okstate.edu/plan...ses/f-7617.pdf

This site discusses anthracnose in trees--we already know it occurs in
roses:

http://pearl.agcomm.okstate.edu/plan...ses/f-7634.pdf

Although certainly not a fruit tree, Dogwoods are quite common around
here and are prone to Cercospora leaf spot, just as roses are.

This UC Davis site discusses the fungus Sphaerotheca pannosa, which
causes powdery mildew, and notes that rosae is one variety of the
disease caused by this fungus--the one on roses.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7463.html

What I was remembering was reading that roses and some fruit trees
share a propensity for fungal disease--not necessarily black spot,
just fungus in general.

Apple and Pear trees are susceptible to scab, which is a disease
caused by the fungus venturia inaequalis. If you look at the photos
on this page:

http://www.caf.wvu.edu/kearneysville/wvufarm11.html

you will see that apple, cherry, and peach trees suffer from a variety
of leaf spot diseases that cause defoliation. While these specific
diseases may not travel from the fruit trees to roses, the conditions
which would foster fungal disease in fruit trees would also do so in
roses.

All of the above may be avoided by the regular application of
appropriate fungicides. If one is willing to do this, one may grow any
rose that strikes one's fancy. I do this and I highly recommend it.