Cankers on Knockout Rose canes - organic remedy ?
Good Afternoon. Using the Missouri Botanic website site's photos I identified the blackened areas on my knockout roses canes as cankers. If I was to prune out all of the effected canes there would only be a few of the smallest left. I read that copper fungicide may be effective. May I have your insight on the best way to move forward? Prune? Treat with copper or another alternative? Sadly I located the issue as I was pruning this year and now understand these new wounds are susceptible to the disease. Thank you for your guidance.
We would suggest that you prune six inches or so below the affected wood. Good hard pruning will be good for your knockout roses. Now is a good time to be pruning. vw