IPM Checklist
Hollyhock Rust: Identification and Sanitation-First Control
The short answer
Hollyhock rust, caused by the fungus Puccinia malvacearum, is the most common disease of hollyhocks. It shows as yellow to orange spots on the upper leaf surface with matching raised orange-to-brown pustules directly beneath on the underside, and it progresses up the plant so the lower leaves brown and die first.
The fungus survives winter in hollyhock leaf and stem debris and on related plants in the mallow family, especially common mallow weeds, which act as a reservoir. Spores spread by wind and by rain or sprinkler splash, and the disease can also arrive on infected transplants.
Because it overwinters in debris and on weeds, control is sanitation-first: remove symptomatic lower leaves early in the season, cut plants back and clear all debris in fall (bury, burn, or bag rather than compost), and pull out nearby mallow weeds. Space and site plants so foliage dries quickly, water the soil not the leaves, and, only where the disease is severe, use fungicides on a regular interval per Extension, rotating active ingredients.
Identifying hollyhock rust
The disease reads clearest from underneath. Wisconsin Extension describes orange-to-yellow spots about an eighth to a quarter inch across appearing on the lower leaves, with brown-to-dark-red raised pustules on the leaf undersides; each pustule corresponds to a yellow spot visible on the upper surface. Those pustules are the fungus's spore-producing structures, and heavily infected leaves develop holes and a lacy, tattered look before turning gray or tan and dying.
The pattern of spread on the plant is itself a clue. Missouri Botanical Garden notes infection progresses upward, so the lowest, oldest leaves are killed first while newer growth up top stays cleaner for a while. Left unchecked, the disease climbs, moves onto stems, and can defoliate a plant from the bottom up over the summer. Because hollyhock rust is so consistent in appearance, it is usually straightforward to identify without a lab, though the general rust-on-plants guide covers how rusts behave across other ornamentals.
Why it keeps coming back
Hollyhock rust returns year after year because it overwinters right where the plants grow. Wisconsin and Michigan State Extension both note the fungus survives winter in hollyhock leaf and stem debris and possibly in living overwintering tissue, then produces spores in spring that infect the new season's growth. Leaving last year's stalks and fallen leaves in place essentially preloads the next year's infection.
The other reservoir is weeds. Missouri Botanical Garden points out that common mallow and other plants in the mallow family in the vicinity can host the same rust and serve as a source of infection for nearby hollyhocks. That is why a scrupulously cleaned hollyhock bed can still get rust if mallow weeds along a fence or path are left standing, they carry the fungus over and reseed it.
Managing it, sanitation first
Attack the overwintering sources. In fall, cut plants back after flowering and remove and destroy all hollyhock debris (bury, burn, or bag it, rather than relying on a compost pile where the fungus may survive). Early in the growing season, pick off and destroy the first symptomatic lower leaves to slow the climb up the plant, and pull out nearby mallow weeds to remove the alternate inoculum. These steps, done every year, are what actually keeps the disease manageable.
Culture makes the sanitation stick. Plant hollyhocks in a sunny, well-spaced, airy spot so foliage dries quickly, and water the soil rather than the leaves, avoiding overhead sprinklers that splash spores and keep leaves wet. Where the disease is severe despite all this, Extensions list fungicides such as chlorothalonil, mancozeb, myclobutanil, tebuconazole, triticonazole, or sulfur, applied on a regular interval (often 7 to 10 days) and rotating active ingredients across applications; follow the label rather than any fixed homeowner dose. Fungicides protect healthy tissue but do not cure infected leaves, so they support sanitation rather than replace it.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Wisconsin-Madison Extension - Hollyhock Rust — Orange-to-yellow spots about an eighth to a quarter inch appear on lower leaves with brown-to-dark-red raised pustules on the leaf undersides, and severely affected leaves develop lacy holes; the fungus survives winter in hollyhock leaf and stem debris and spreads by wind, rain, and sprinkler splash; management is to remove fall debris and symptomatic leaves, eliminate mallow weeds, space plants for air circulation, avoid overhead sprinkling, and use fungicides (chlorothalonil, mancozeb, myclobutanil, tebuconazole, triticonazole), rotating active ingredients.
- Missouri Botanical Garden - Rust of Hollyhock — Yellow circular spots about an eighth inch form with swellings and blisters on leaf undersides, infection progresses upward, and heavily affected leaves turn gray or tan and die; the fungus overwinters in plant debris and possibly living tissue, and nearby common mallow weeds can be a source of infection; controls include disease-free seed, spacing in a dry sunny site, removing and destroying old plant material at season's end, destroying mallow weeds, keeping foliage dry, and fungicides at 7 to 10 day intervals.
- Michigan State University Extension - Hollyhock Rust (Puccinia malvacearum) — Hollyhock rust is caused by the fungus Puccinia malvacearum; lower leaves show symptoms first and the disease progresses to upper leaves over the summer, with brown spots on the underside and raised bright yellow-orange pustules; spores overwinter on diseased tissue and are produced on susceptible mallow-family weeds; sanitation (cutting plants back after flowering, removing and destroying debris, controlling mallow weeds) plus fungicides for severe cases are recommended.