Hi Cindi,

I have 4 knockout roses that get gray spots on them every year. The spots then make holes in the leaves. The buds seem to do well and this year I have been spraying a special rose spray for insects and diseases on them every week as instructed. This has been for about 4 weeks. So far I have seen no improvement! Any advcie on how to combat this and prevent it each year? Thanks!

Knockouts are disease resistant, the key word here is “resistant”; they will occasionally succumb to some disease problems.
If you start to see black spot, you can cut them back to remove any damaged stems and leaves---and get that debris off your property—and then fertilize to stimulate new growth. Using a fungicide spray until the new growth matures somewhat will help prevent the disease from coming back.

Keep in mind that a fungicide is a preventive treatment; fungicides will not get rid of existing disease, but they will help to prevent the disease from taking hold if applied regularly from the beginning of the growing season. Always follow the label directions carefully when applying pesticides.