Rust on Black-eyed Susan's
My Susans have rust. Do I need to destroy the entire plants and start anew next year? More importantly, should I treat the area where they were located to prevent this from happening again? And will I ever be able to plant in these locations again?
Rust is not as common on black-eyed Susans as Septoria, another fungal disease. We'd like to see photos to be sure of the diagnosis.
If it is rust, you do not need to destroy the plants. Remove the leaves at the end of the season and discard in the trash.
Please read about Rudbeckia leaf spot diseases on our webpage (bottom) and read the link provided with its helpful diagnostic chart.
Thanks so much for your response! I do not have a photo to show you because I removed all the Susans to the ground (not the roots). However, if indeed my Susans had the leaf spot disease that you suspected, the question remains, should I dig up all the below-ground material and then not plant Susans in the same spot?
You could let them be and see if the disease is as bad next season. Some years are worse than others.
That said, septoria has been quite a problem and the best option is to remove the plants and grow something else there.
Thanks, again, for your response. If I leave them be and the blight returns next year, would Neem have any effect? Wouldn't traces of the disease be present to infect new Susans planted in the spring of next year?
Neem has not proven effective for septoria leaf spot.
You have removed the infected plants. Try to clean up the surrounding soil surface if a lot of dead leaves have fallen there. You will be lowering the amount of diseased material, but there are always some spores floating around in the landscape. You may find that your black-eyed Susans are fine most of the time in years when we do not have long periods of rain.https://www.extension.umn.edu/garden/yard-garden/flowers/diseases-of-rudbeckia/
Be sure to keep your rudbeckia well spaced for good air circulation and quick drying after rains. No overhead watering.