disease of my swamp sunflower
Around my pond them there is a nice patch of Swamp sun flower.Last year they were almost destroyed by a disease.Brown patches appear and the leafs turn black as if something have burned them off.The plants survived and came back.But now the patches are coming back again.Any body knows what this disease is and how to treat it?
Certified GKH Gardening Expert
A leaf spot disease could be a virus or bacterial disease.
I would suggest removing the plant and discarding.