three rose problems
I have several rose plants and I think that there are three distinct problems going on. Would you please let me know what you think is wrong and what the best ways to treat the is?
On my climbing Graham Thomas rose, there are reddish spots on the leaves, but they don't look like what I'd expect rust to look like. On my Wollerton Old Hall rose, as well as several others, there's a black substance on the leaves that wipes off. I treated it today with neem oil. Finally, my Jude the Obscure rose has some leaves with a sort of mottled yellow and green appearance.
Thanks for your help!
Montgomery County Maryland
The symptom in your first photo (rust colored spots) looks like the early stage of cercospora or a reaction to black spot disease. The holes in the leaves are from rose slug sawfly feeding. In your second photo, there is black spot. The third photo (with the yellow blotches on the leaves) shows symptoms of a virus. Read the following pages for information about these problems in roses and how to manage them:
The black substance that rubs off is probably sooty mold, which is a sign that there were aphids. https://extension.umd.edu/hgic/aphids-flowers
Leaf spot diseases such as cercospora and black spot are very common in roses and can be very persistent. You can use a registered fungicide labeled for roses and apply it according to the product instructions. It can help manage the disease, but will not "cure" symptoms that are already there. https://extension.umd.edu/hgic/fungal-leaf-spots-shrubs
For further information about rose care, you might be interested in connecting with one of the rosarians at the Potomac Rose Society. http://potomacrose.org/
Thanks so much. This is really helpful information.