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Blackspot on roses near tree
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. |
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