These photos, of my once beautiful white rose bush, tell the story of what prompted some research!
What you see is the result of "Diplocarpon rosae" commonly known as "Black Spot Disease".
It is a serious fungal disease common in humid climates. It starts on the leaves, spreading across, and eventually killing them. A serious case of bad spot can leave your rose bush completely bare of leaves. It is advised that whenever you see a case of black spot you promptly remove and destroy any infected leaves. (I wish I had researched this sooner!) Also, remove any leaves from the ground that have already fallen. It is important to REMOVE all affected leaves as Black Spot is spread from leaf to leaf by water. So, the next good rain will likely cause the development of more of the fungus.
The safest (non-chemical) way to prevent Black Spot is to combine 1 Tablespoon baking soda, a few drops of dishwashing liquid detergent, & 1 gallon of water. Mix thoroughly and spray both sides of the leaves once a week.
For more information on Black Spot Disease in the state of Indiana go to:
http://www.ppdl.org/dd/id/rose_black_spot.html
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