Black spots on Black Eyed Susan leaves

Asked August 9, 2013, 12:48 PM EDT

I have black spots showing up on many of the leaves of my black eyed susans. They eventually turn the whole leave black and it starts to die. I have seen this on Black Eyed Susans in other locations so I don't think it is a problem in my garden alone. How can I prevent this ailment/disease?

Westchester County New York

1 Response

It is not possible to diagnose a disease with 100% certainty without seeing the plant. If possible take a sample to your local Extensions Office for identification. That said, Black-eyed Susan (Rudbeckia) tends to contract a disease called Septoria Leafspot. The disease shows up as irregular black spots on the leaves. This can disfigure the plant significantly if the weather is favorable, wet, hot and humid. Once established, it is difficult to control. Try to encourage air movement to reduce leaf wetness. Removing infected leaves if there are only a few helps. A general purpose garden fungicide may also help reduce the spread of the disease, but these chemicals are protectants and do not cure infected leaves (check label for instructions on spray). At the end of the season really clean up the area well, discard the infected plant material, don’t put in your compost pile.