Weird growths and black spots suddenly appeared on my rudbeckia plants
What is this- a virus? I check the garden daily and the black spots appeared and spread within 2 days. I am concerned it may spread to a large new planting in another area of the lot. If it is a virus which other plants would be susceptible? I have cutleaf coneflower and echinacea in the other plot. Thank you!
Montgomery County Maryland
We looked at the photos and we cannot be sure of what you are dealing with.
We are not sure why there is a green spot in the middle of the dark area on the foliage. Open it up and see if something is in there. Perhaps it is a gall (insects, growths), etc.
You can let us know and send more photos.
Also, You did not mention the type of rudbeckia you have. The variety Goldstrum is very susceptible to Septoria leaf spot. This is common in rainy weather, as the spores are spread by splashing water. promote good air circulation and don't let the plants get overcrowded. You can remove old leaves that turn black. Be sure to remove all old infected material before next spring's new foliage starts coming out.
If you have 'Goldstrum', you also might want to replant with newer varieties of rudbeckia that are more disease resistant.
Upon closer examination the green spot in the middle doesn't appear to be a gall or other blister type formation. It seems like more of a bulge of the original leave. I do not know which species of rudbeckia they are. They were here when we moved in and when I removed another plant from this area they moved in and seemed to thrive there. And they are overcrowded. I will remove them, discard and plant something else next year. Thanks!