Knock Out Roses getting TKO
I have several Knock Out Roses, and the ones facing a southern exposure look awful. They started out with a lovely spring bloom. Now, the flowers look stunted, the buds form but don't open and shrivel up and turn brown. Also noticing m any spots on leaves, is this anthracnose? Eight bushes are affected. I've been trimming off the affected blooms but there are many of them.
Your Knockout roses may be suffering from Botrytis Blight. However, for a definitive diagnosis and management recommendation please take a sample of a cane that includes blooms and buds as well a woody section. Bring it to your County Extension Office at 16483 County Seat Highway, Georgetown, DE weekdays between 8am and 4:30pm.