Answer: Knockout roses are some of the most disease resistant roses around, but if the growing conditions are not quite right, or the plants are under stress, they can develop disease problems. I can't tell without examining the plants just what the problem might be, but you may be able to control disease and insect problems by pruning your plants back to remove fungal spores and insect eggs. Wait until the plants are dormant in late winter and prune them back, removing all the pruning debris from the garden. Or, you can wait until early spring to prune them - just before new growth begins. Hope this helps!
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