Is this rust on my black eyed Susan’s?

Question: Hello, 

Some of my black eyed Susan’s have turned completely brown when five feet away the other ones are still have green leaves and blooms. Is this a rust issue? Should I remove these plants completely to prevent further spread? 

Also, behind these used to be a tall monarada variety (maybe raspberry splash?) and it didn’t come back this year.  Is this fungus maybe in the soil? 

I attached two pictures.  The infected plants and the ones uninfected across the way. 

Thanks,
Jennifer

responder: An Ask Extension Expert Replied September 19, 2024, 11:20 PM EDT
response: Thanks for your question. I don’t think that the demise of your monarda is related to the issues that you are now seeing with your Black Eyed Susans. While it would be difficult to prove a correlation, I suspect it is just a coincidence. When I observe a situation in which only a portion of a garden shows stress, I first think that some type of herbicide might have contacted that portion. This selective occurrence would not be expected for fungal diseases such as rust. Have you, your neighbors, and/or lawn service recently applied any type of weed killer to your yard or adjoining yards? See: https://extension.umn.edu/node/40266 - :~:text=Herbicide drift happens when herbicides,popular lawn and crop herbicides. I cannot tell from your pictures whether your Black-eyed Susans (Rudbeckia hirta) are experiencing a rust infection. There are many possibilities that might also exist: 1). Powdery Mildew. Symptoms would include white or gray powdery coating on leaves, stems, and buds. This could be caused by high humidity, poor air circulation, and warm temperatures.  If this is the situation, improve air circulation around the plants by selective removal of stems. This might be part of your customary fall clean up. 2). Leaf Spot (Cercospora rudbeckiae). Look for small dark spots on leaves that may enlarge, causing yellowing and defoliation. This fungal infection typically occurs under wet and humid. Remove all affected plants and discard in the trash. Clean up any fallen plant debris. 3). Rust. Look for orange or reddish pustules on the undersides of leaves, leading to leaf yellowing and defoliation. 4). Septoria Leaf Spot. Symptoms include dark brown to black lesions on the leaves, leading to defoliation. To prevent fungal diseases in black-eyed Susans, ensure good airflow around plants, avoid watering leaves, and practice crop rotation and proper garden hygiene by cleaning up debris in the fall. Here is some information on these and related points: https://portal.ct.gov/caes/plant-pest-handbook/pphr/rudbeckia-blackeyed-susan-rudbeckia https://extension.psu.edu/rudbeckia-diseases https://www.gardeningknowhow.com/ornamental/flowers/black-eyed-susan/rudbeckia-leaf-spot.htm However if you really want to get to the bottom of things, consider submitting plant samples to a diagnostic disease laboratory for an analysis. This would be a definitive way of getting to the bottom of things. The University of Wisconsin has an excellent facility at which to do this. Before submitting anything to them, call first as to what type of samples should be submitted. They have a nominal charge for their analysis. See: https://pddc.wisc.edu/clinic-overview/ If you perform a good fall clean up, I would expect that you will not see a recurrence of this in 2025.Good luck. Please get back to us with any additional related questions.

responder: The Question Asker Replied September 20, 2024, 7:36 AM EDT
response: Thank you for this robust answer. The Monarda did have powdery mildew the year prior but still bloomed just fine and had always come back.  It had been there for numerous years. It didn’t return this year, This is the third year the BES have been in that spot, but the first year they’ve had this issue.  It’s was a much wetter site this year than in years past (as many of us experienced!) They did not have powdery mildew, but I will take a look at the other links you shared to see if I can figure it out. We do not use any herbicides or chemicals. And neither do my immediate adjacent neighbors.   Thanks! Jennifer -- Jennifer Foth <personal data hidden>On Thu, Sep 19, 2024 at 10:20 PM Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied September 22, 2024, 8:01 PM EDT
response: Thanks for getting back to us.  Good luck.  Let us know if related questions arise.