Black eyed susans
My entire bed of black eyed Susan’s died early last summer due to a fungus. Now this summer my black eyed Susan’s in the same bed are also,dying of a fungus. Should I have amended the soil?
You are probably seeing symptoms of Septoria leaf spot, a fungal disease of Rudbeckia plants. Septoria leaf spot symptoms start as small (1/8 inch) round dark brown spots on lower leaves that may enlarge to twice that size and extend to upper leaves as spores are spread by splashing water from rain or irrigation. Another problem in Rudbeckia is Angular leaf spot. These are two primary diseases that cause black-eyed Susan leaves to get black spots that progress to black blotches and sometimes totally black leaves.
Management for both Septoria leaf spot and Angular leaf spot are the same. Plants are not usually killed but can die back to the base. To manage these diseases, do not water overhead. Keep plants thinned so they have good air circulation and dry quickly after rains. At the end of the season (or earlier if the plants look dead), remove all infected plant material and discard in the trash so that infected plant material will not reinfect them next year. You can spray with a fungicide containing copper for Septoria (a fungus.) You can use a copper-containing bactericide for Angular leaf spot.
The variety 'Goldstrum' is notoriously susceptible to angular leaf spot. If you have this variety (it sounds like yours are highly susceptible), consider replacing with resistant varieties.
The native Rudbeckia hirta (short-lived perennial) is highly resistant and seeds itself so freely that it's like having a perennial plant.
Thank you for your help.