I live in windsor ontario canada, my roses do this also, I've tried fungicides, but hate having to re-spray after rain. I got a product called earth crystal( pryoclitic clay) and I scratch a tsp around each plant in spring and water it in. I don't do anything else. My roses don't suffer from blackspot/powdery mildew, and if they are fragant it seems to enhance the fragance also. This product is 100% organic, it's fairly inexpensive, and available from any grotek dealer.
|