Hollyhocks just get rust........it is pretty much a hollyhock fact of life and there's not a lot you can do for it. You could try some fungicides early in the season before you see any signs of the problem (fungicides tend to be only preventatives, not curatives and must be applied before you notice symptoms) but I have not found any that really address rust - on any kind of plant - well. Hollyhock rust is restricted only to members of that family (Malvaceae) so no worries about it spreading ramapntly throughout the garden. And there are 'supposedly' rust-resistant forms: Alcea ficifolia and A. rugosa or Russian hollyhocks tend to be better with this issue than the common, garden variety. Rust generally does not kill plants but just disfigures them to various degrees. Removing the affected foliage and destroying is about the best you can do, although mulching around the base of the plants will help prevent fungal spores from splashing up and reinfecting.

pick the infected leaves off - and you'll have to search on this but there is a weedy plant that is the host to hollyhock rust. If you can find it nearby, dig it out and destroy it. I got rid of hollyhock rust that way in a former garden. I think I found it in an Extension Service bulletin and was surprised that I did indeed have that weed nearby. You can also spray with Messenger, dust with corn gluten in the spring but there isn't much to do to kill it now.

It really doesn't matter what Hollyhock you wish to grow, unfortunately the risk of getting rust is always there since the culprit can be in the soil, seed, or plant and not be seen until the plant gets big enough for you to have a nice hole in the garden if you take it out. I love these plants and was told that the fig leaf variety did not get rust. NOT! It does. :( I also grow Alcea Kurdica, and Alcea Rugosa which were not suppose to have rust but did. Another relative, Althaea Officinalis (Marshmallow Plant) also used to show signs of rust. The trick for me was to apply corn meal to the soil and treat any signs of rust with garlic oil. At the end of the season, all stems were cut back and wilted foliage was removed when the plant disappeared for the winter. Good compost and corn meal was applied as a mulch. This was repeated again in the spring when the plants emerged. In the first year I began treating the rust, I sprayed any rust with garlic oil spray - you can find recipes by googling. Simple to make and apply. If the problem was too bad, I would cut the plant back, but not remove it. Just start over again. This summer, I've not had to do the garlic thing for HH rust. (Did some anyway as I found it also deters deers...) The results have been good. I am now growing nice healthy looking Hollyhocks.

Yes, the number of prolegs are an identifying feature, taz, but most folks don't know that term. You might want to explain it to someone needing an ID. Proper ID is so important. I jumped to the conclusion that her critters are sawfly larvae because of the description of the damage ( typical for this sawfly), because of the species of plant (if you have hollyhock or other members of the mallow family, you'll often be plagued by this insect, and by nancy's use of plural when mentioning the 'worms'. Sawfly larvae are never lonely for each others' company. Add to that your explanation of the proleg feature, and there's not much chance of a missed ID! Here is a link that might be useful: Hibiscus (hollyhock) sawfly larvae on Google