Soil

Asked September 21, 2020, 4:00 PM EDT

Do I need to replace the soil that may have sporesfrom black spot from my roses. I am planning to use the area for other plants and vegetables after removing the roses.

Washington County Oregon

1 Response

Thank you for your question. Although black spot is a fungal disease of roses, occurring most often in the spring, there are other diseases that cause black spots, wo, without a photo of the problem, we cannot tell you whether the source is fungal or bacterial. You can read about the possibilities here: https://pnwhandbooks.org/plantdisease/host-disease/dogwood-cornus-spp-leaf-spots

(This says dogwood, but dogwoods and roses are both in the Cornus family, so acquire similar diseases.) These diseases are spread through the air, not the soil, so the best things you can do are those listed under the "Control" sections. Since fungicides only kill fungi, they aren't helpful for bacterial infections. Rake up the leaves; don't water overhead, and, if you're so inclined, replace with a cultivar that is resistant to these problems. If, after taking these steps, you have spots next spring, take clear, closeup photos, and submit them here, so we can identify exactly what they have. There is nothing you can or should do about the soil, although some bacteria overwinter if you put on mulch too deeply. I hope this is helpful. Good luck!