Q: Something is devouring my hollyhocks. There are yellow dots on the underside of affected leaves. Eventually, the leaves look like lace. What can I do to get rid of the problem?
A: You have hollyhock rust. The disease causes lots of orange-yellow pustules underneath hollyhock leaves and corresponding yellow dots on top. Thousands of spores are in the rust pustules. They are carried by splashing water and breezes to nearby healthy plants and cause new infections. The fungus overwinters in infected plant debris.
Spray now with a fungicide containing chlorothalonil, mancozeb, sulfur, neem oil, or myclobutanil. To break the disease cycle, cut all of your hollyhock stalks back to ground level in the fall. Afterwards, collect all leaves and destroy them.
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