How do you manage rust on hollyhocks?
Every year my great hollyhocks are practically destroyed by RUST. They enjoy full sun and super air circulation. I trim, sanitize my tools constantly and use fungicides to no avail. Wondering if you have any advice? I am thinking of digging and destroying them as it’s way too time consuming at this point.
You are already doing two important things when attempting to control any plant infection, as well as just working with your plants in general: trimming and removing the infected tissue and sanitizing your tools to prevent further transmission. Kudos to you for both practices. The bad news is that rust on hollyhocks (caused by Puccinia malvacearum) is very difficult to control, especially if it gets established, as it sounds like it has here.
I will refer you to this great Univ of Wisconsin fact sheet on Hollyhock Rust, which details how best to approach fungicide application. In particular, “If you decide to use fungicides for control, select products that are labeled for use on hollyhocks (or more generally on ornamental flowering plants) and contain the active ingredients chlorothalonil, mancozeb, myclobutanil, tebuconazole, or triticonazole. When making more than one application, DO NOT use the same active ingredient for all treatments. Instead, alternate the use of at least two active ingredients with different modes of action to help minimize problems with fungicide-resistant variants of the hollyhock rust fungus. Myclobutanil, tebuconazole and triticonazole have similar modes of action and should NOT be alternated with one another. [emphasis mine]” If you’ve not tried this approach, alternating active ingredients might improve the situation.
Also important on the site is environmental advice on what else can be done in your garden to minimize the impact of the rust, some of which you are doing, but some of which might be a burst of inspiration. Planting the hollyhocks to maximize air flow, minimize overhead watering, removing other members of the Mallow family in your garden, etc. As a final resort, you can always remove the hollyhocks and look for varieties or cultivars to replant that are rust-resistant.