Rust on Plants: How to Identify and Control Orange Rust Fungus

By the Garden Voila editorial team · Updated October 27, 2026 · How we verify

Rust is a group of fungal plant diseases named for the orange, yellow, red-brown or black powdery pustules they produce, mostly on the undersides of leaves, which rub off like rust dust on your fingers. Common garden rusts affect hollyhocks, roses, snapdragons, daylilies, beans, garlic, onions, asparagus, mint, geraniums, fuchsias, lawn grasses and fruit trees such as apples (cedar-apple rust). Infected leaves develop pale or yellow spots on top, turn yellow or brown and may drop early, weakening plants. To control rust, remove and destroy infected leaves early, improve air flow, water at the soil in the morning, clean up debris in fall, grow resistant varieties, and, for valuable plants, apply a fungicide labeled for rust at the first signs.

Garden rust diseases at a glance

What is plant rust?

Rusts are fungi in the order Pucciniales, one of the largest groups of plant pathogens, with more than 7,000 species. The Wikipedia article on rust fungi explains that most are highly specialized, infecting only one plant species or a small group of related plants, and many have complex life cycles with up to five spore stages, some requiring two unrelated host plants, as cedar-apple rust does. Rust fungi are obligate parasites: they can only grow on living plant tissue. The University of Minnesota Extension guide to rust in the flower garden notes that most garden rusts are favored by moist conditions and that removing infected leaves and improving air flow are the first lines of defense.

How do you recognize rust?

• Powdery pustules, orange, yellow, red-brown, brown or black, mostly on the undersides of leaves, sometimes on stems and flowers.
• Spores that rub off on your fingers or a white tissue like colored dust.
• Yellow or pale spots on the upper leaf surface above the pustules.
• Yellowing and browning leaves that may drop early.
• Stunted, weakened plants with fewer flowers or smaller harvests when rust is severe.
• Swollen, distorted tissue or galls with some rusts, such as cedar-apple rust on junipers.

Rust is easy to confuse with other spotty problems. Fungal leaf spots do not form raised, dusty pustules; downy mildew forms fuzzy growth rather than powder; and some insects leave orange or brown droppings. The plant problem identifier can help narrow it down.

How does rust spread?

Rust fungi produce enormous numbers of spores that are carried on wind, sometimes over long distances, and splashed by water. Spores need free moisture on the leaf for several hours to germinate and infect, so dew, rain and overhead watering all encourage infection. Many rusts are most active in mild temperatures, roughly 60 to 75°F, with humid nights. Some overwinter on infected leaves and debris, others on living plants (such as hollyhock rosettes and mint stems), and some on an alternate host plant. Because spores blow in from elsewhere, you cannot always prevent rust entirely, but you can greatly reduce its impact.

How do you treat rust on plants?

1. Remove infected leaves as soon as you see pustules, picking them off carefully and bagging them so spores do not scatter. On hollyhocks, remove the lowest leaves, where rust often starts, regularly through the season.
2. Cut back badly infected plants. Perennials such as mint, hollyhocks and daylilies can be cut to the ground after flowering; new foliage often emerges clean.
3. Improve air flow by thinning stems and spacing plants; see the plant spacing calculator.
4. Water at the soil, early in the day, and avoid wetting leaves. The garden watering calculator helps plan deep, efficient watering.
5. Use a protective fungicide on valuable plants, starting at the first sign and repeating as the label directs. Products labeled for rust include sulfur, myclobutanil, propiconazole, tebuconazole and some copper and biological products; check that your plant and rust are listed. Fungicides protect new leaves but do not cure existing pustules.
6. Feed moderately; lush, high-nitrogen growth is more susceptible.

Rust on hollyhocks

Hollyhock rust is so common that many gardeners consider it part of growing hollyhocks. It overwinters on living leaves at the base of plants and on debris, and infects new leaves in spring. Remove all old foliage in fall and again in early spring, pick off the lowest infected leaves every week or two, space plants widely in full sun, and avoid planting near mallows, which also host the rust. Some gardeners grow hollyhocks behind other plants so the lower, rusty leaves are hidden. Rust-resistant types such as fig-leaf hollyhock (Alcea ficifolia) and some hybrids perform better. See when to plant hollyhock seeds for growing tips.

Rust on roses

Rose rust causes bright orange pustules on the undersides of leaves and sometimes on canes, especially in cool, moist coastal climates such as the Pacific Northwest and California. Remove infected leaves, prune for air flow, clean up fallen leaves, and choose resistant varieties. See black spot on roses and our rose garden guide for other rose diseases.

Rust on beans, garlic, onions and asparagus

Bean rust produces reddish-brown pustules that can defoliate plants in warm, humid weather; plant resistant varieties, rotate crops, avoid working among wet plants and remove debris after harvest. Garlic and onion rust (Puccinia allii) causes orange pustules on leaves and reduces bulb size, especially in mild, humid climates; rotate alliums, space plants, avoid excess nitrogen and remove infected debris. Asparagus rust appears on the ferns in summer; cut and remove ferns in late fall, grow resistant varieties such as Jersey Knight and Mary Washington types, and keep ferns growing vigorously. See how to plant garlic in fall for garlic care.

Rust on lawns

Lawn rust turns grass yellow-orange in late summer and fall, leaving orange dust on shoes, pets and mowers. It is most common on slow-growing lawns under stress, especially Kentucky bluegrass and perennial ryegrass. Fertilize appropriately, water deeply in the morning, mow regularly with a sharp blade and bag clippings while rust is active. Lawns usually outgrow rust once growing conditions improve. See our lawn care calendar for seasonal lawn tasks.

How do you prevent rust?

The University of Wisconsin Plant Disease Diagnostics Clinic fact sheet on hollyhock rust recommends thorough cleanup and removal of infected leaves as the foundation of rust management in perennial gardens.

• Grow resistant varieties of beans, roses, snapdragons, hollyhocks, daylilies and asparagus.
• Clean up debris in fall and early spring, removing infected leaves and old stems.
• Space plants for air movement and give them full sun.
• Keep foliage dry with drip irrigation and morning watering.
• Rotate vegetable crops, especially beans and alliums.
• Remove alternate hosts where practical, such as galls on junipers near apples or wild mallows near hollyhocks.
• Inspect new plants before buying; avoid any with pustules.

Dealing with more than one problem? Our plant pests and diseases guide lists every insect and disease we cover, organized by symptom.

Rust FAQ

What does rust look like at different stages?

Many rust fungi change appearance through the season as they produce different types of spores. Early in the year, some form small orange or yellow cup-like structures on leaves. In summer, the familiar powdery orange or cinnamon-brown pustules appear and release spores that spread the disease rapidly. Late in the season, many rusts produce dark brown or black pustules containing tough resting spores that survive the winter on debris. Seeing black pustules on fall leaves of hollyhocks, beans or asparagus is a sign the fungus is preparing to overwinter, which is why thorough fall cleanup matters so much.

Is rust worse in some climates?

Rust fungi need moisture on leaves to infect, so they thrive in regions with frequent dew, fog or rain and moderate temperatures, such as coastal areas, the Pacific Northwest and the humid East. Hot, dry weather slows most rusts, though they can still develop where dew forms overnight. In greenhouses and sunrooms with high humidity and condensation, rust on fuchsias, geraniums, snapdragons and chrysanthemums can be persistent. Ventilation and keeping foliage dry are the most important controls indoors.

Can you compost rusty leaves?

It is better not to. Many rust spores survive in leaf debris and cool compost, returning to the garden with finished compost. Bag rusty leaves for the trash, or bury them deeply away from susceptible plants. Hot compost piles that reach 140°F or more throughout can kill spores, but most home piles do not heat evenly.

Should you replace rust-prone plants?

If a plant is covered in rust every year despite good care, replacing it with a resistant variety or a different plant is often the easiest solution. Many modern roses, snapdragons, beans and daylilies are bred for rust resistance, and catalog descriptions usually note it. In mixed borders, siting rust-prone plants such as hollyhocks at the back, where lower leaves are hidden, also helps.

Which rusts need two different host plants?

Some rust fungi cannot complete their life cycle on one plant. Cedar-apple rust alternates between junipers and apples or crabapples; white pine blister rust alternates between five-needle pines and currants or gooseberries; and some grass and cereal rusts alternate between grains and barberry or buckthorn. For these rusts, removing the alternate host within a few hundred yards, or choosing resistant varieties, can break the cycle. Other rusts, such as hollyhock, rose, bean, snapdragon and daylily rust, complete their whole life cycle on a single host, so sanitation and resistant varieties are the main tools.

What is daylily rust?

Daylily rust appeared in North America in 2000 and spreads quickly on susceptible cultivars in warm, humid regions. It causes bright orange pustules on leaf undersides, with yellow streaks on the upper surface. Buy plants from reputable nurseries, inspect new daylilies carefully before planting, cut back and destroy infected foliage, and choose cultivars rated resistant. In colder regions the disease usually dies back in winter, but reintroduction on new plants is common.

Rust on mint, snapdragons and fuchsias

Mint rust causes swollen, distorted shoots in spring followed by orange pustules; dig out infected patches and replant clean runners in a new spot. Snapdragon rust produces dark brown pustules that can kill plants by midsummer; grow resistant series and water at the base. Fuchsia rust is common in greenhouses and hanging baskets; remove infected leaves, improve air flow and avoid misting foliage.

A seasonal rust checklist

• Late winter: clear old foliage of hollyhocks, roses and perennials; prune for air flow.
• Spring: space plants well, water at the base and begin weekly leaf checks on susceptible plants.
• Summer: pick off spotted leaves early; use protectant sprays only on plants with a history of severe rust.
• Fall: remove and bag infected leaves; note which varieties suffered so you can replace them.

Sources: University of Minnesota Extension, Rust in the Flower Garden; University of Wisconsin Plant Disease Diagnostics Clinic, Hollyhock Rust; Wikipedia, Rust (fungus).