I have recently learned about Alternaria and I think I recall seeing it on a few rose canes last spring. This is a new problem in my PNW garden. What can you tell me about this? Is it a fungal disease?
Sorry to hear that you are possibly facing a “new” problem in your garden. What signs or symptoms make you think you may have Alternaria in your garden?
I was reading a newsletter from So. California and thought about this photo I had taken during spring pruning. I remember wondering what was going on with the older looking canes.Any thoughts?
Sorry, I am no help. If it were my plant and I really was worried about it, I would send the photo to Dr Allen Owings or Dr Mark Windham. How did the plant do during this past growing season? Was the plant still strong and vigorous or did the problem spread?
I would love to know more about this as well
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Google shows many responses about Alternaria, most of which are rather alarming. https://www.tomatonews.com/en/eu-the-commission-investigates-alternaria-toxins_2_2013.html
Elena, Alternaria is a soil fungal pathogen. You might want to take samples of the stems that you are questioning to a plant pathology lab. I don’t know how close you are to Washington State University but they have great resources that could help you. I used to do a lot of cooperative work with colleagues there so I know that they are very reliable. Outside of this, it is all guesswork as to what might be wrong with your roses. To me it looks like weathered canes maybe suffering from a spotted disease such as black spot, Botriytis, etc. I would apply a copper dormant spray and see if that will solve the problem with these fungal diseases.
Thank you Baldo. I need to learn more about this soil pathogen.
I to would like to learn more about this
Chlorothalinil (Tradename Daconil) is recommended for Alternaria.