Answer: I apologize for the delay in answering your question. There are a number of pests that feed on hollyhock foliage and there are some foliar diseases such as rust that can disfigure the plant in a hurry. Typically they do appear in early summer, often when the plants are in full bloom. An occasional plant will also succomb to a root rot or other unseen problem when stressed by heat and the energy devoted to blooming.
Generally, although you can try to treat the plants with a fungicide, it is usually a losing battle. The plants are usually biennial, meaning they bloom the second year, set seed and then die anyway. For this reason too, for most gardeners it is not usually worth trying to salvage the foliage. This is why hollyhocks are often grown to the rear of a bed or "out back" where the leaves will not be seen up close. Also, it is important to clean up any debris from the plants each fall. This helps delay and can help minimize the onset of problems the following year. It can also be helpful to pick off the first leaves to show problems, to try to delay the disfiguration a little longer.
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