Answer: The rust colored spots are the fruiting spores from a disease called rust. The spores will spread to other leaves unless the disease is treated with a fungicide. Pick off the infected leaves and remove them from the garden. You can then spray the remaining canes and branches with a fungicide, to make sure all of the disease is stopped in its tracks. You'll be doing your plants a favor by pruning - you'll also open them up to better air circulation, which will make them less susceptible to fungal disease.
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