Answer: How disappointing for you! The white stuff on the mulch indicates too much water (which encourages fungal growth). That's your first indication that there's something going on with the roots. Rake the mulch away so you can check the soil for excess moisture. Knock Out roses need to be watered deeply but infrequently. Too much water can drive oxygen from the soil and effectively suffocate the roots. Water your roses as usual and then wait 3-4 days and dig down into the soil. If it is still moist an inch below the surface, you won't need to water again for a few more days. If the soil is dry one inch below the surface, it's time to water. With a little experience you'll be able to tell how long you need to run the water to get the soil moist all around the root system, and how long it will take to dry out between waterings. The second thing you should do is prune the plants down by about one third, both to remove most of the disease and to encourage healthy new growth. After pruning, treat with a fungicide such as Ortho's Rose Defense. This neem oil based product will take care of diseases and insects. Give your roses the rest of the gardening season to recover. If they still look bad this winter, prune them all the way down (to within a few inches of the graft). In the spring apply Rose Defense to keep black spot at bay. With any luck at all your roses will recover and develop healthy new stems, leaves and flowers. Hope so!
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