I may be totally wrong, but I think those are just old leaves and I pull them off. It may be some leaf streak but still I just pull them off. I end up with large buckets full of deadheaded blooms and dying leaves almost every morning. I keep reading the way to treat diseased leaves is to pull them off, but I also read that it is taking away the energy of the plant when you pull the leaves. But, when I did not pull the leaves and the old brown scapes the plants looked totally awful. Then the other day I watched a video that reinforced the idea of pulling off the dying old leaves. It stated that the plant would shed the leaves on its own, but it would take a period of at least two weeks for the plant to look green and fresh again and by pulling them off as they turned brown or even yellow you could avoid mostly avoid that two week period. Now it may be that my plants will suffer in the future and become weaker, but I will say my garden looks so much better overall that it is worth it to have the plants look so much better. I just could not stand having all those dying brown and yellow leaves showing along with the brown dying scapes. I am going to harvest a lot of my proliferations today, so I can let the dying scapes go ahead and finish up so I can pull them . The scapes with seed pods and proliferations turn brown at the tops but stay green for a long period and I don't like that look.
Here is the video I watched, and I use a bucket like that big black one in the video and I often pull two or three bucket fulls of old scapes and leaves in a single morning.
https://www.youtube.com/watch?...
