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Rust

Rust

Uromyces and Puccinia species

Fungalalso: Leaf rust

A group of fungal diseases that dot leaves and stems with raised, rusty orange, brown, or yellow pustules of powdery spores. Rusts strike beans, garlic and onions, asparagus, corn, and many flowers, and a brush against a badly infected plant leaves an orange smudge. Damp, mild weather and crowded plantings favor them.

🔎 How to spot it

Look for small raised bumps, the pustules, on the leaves and sometimes stems and pods, that break open to release powdery rusty orange, reddish-brown, or yellow spores that rub off on your fingers. Pustules are often ringed by a yellow halo, and heavily infected leaves yellow, dry, and drop. Each rust tends to be specific to one crop or plant family.

🥀 Damage it causes

Rust pustules destroy leaf tissue, and a heavy case yellows and kills the foliage, weakening the plant and reducing yield. On crops grown for their leaves or stems, such as garlic, onion, and asparagus, the damage directly cuts the harvest. Early, severe infections do the most harm.

🔬 What causes it

Rusts are caused by fungi such as Uromyces and Puccinia species that need leaf moisture and mild, humid weather to infect and spread. The powdery spores travel on wind and splashing water from plant to plant, and many rusts overwinter on crop debris or on living perennial and weed hosts. Crowding, shade, and prolonged leaf wetness all increase risk.

🛡️ Prevent it

Plant resistant varieties and give plants full sun, wide spacing, and good airflow so leaves dry quickly. Water at the base rather than overhead, and avoid working among wet plants. Pull rust-prone weeds, rotate annual crops, and clean up and destroy infected debris at season end so spores do not carry over.

🧯 If it is already here

Pick off and destroy the first rust-spotted leaves and remove badly infected plants. Improve airflow and keep the foliage dry. If rust keeps advancing on a valued crop, an approved organic fungicide such as sulfur, applied early per the label, can slow it. Do not compost infected material, and clear all debris at the end of the season.

💡 Good to know

Most rusts are highly host specific, so the rust on your beans will not jump to your garlic, and some have complex life cycles that require an alternate host plant to complete. The easy field test is the rusty powder that rubs off on a finger, which separates rust from leaf-spot diseases that stain but do not shed spores.

🌱 Plants it affects

714 plants in the library can be affected by this problem

Acorn SquashAdirondack Blue PotatoAdzuki BeanAfrican Blue BasilAfrican MarigoldAgapanthusAgeratumAgrimonyAji Amarillo Pepper🍓Albion StrawberryAlice du Pont Mandevilla🥔All Blue PotatoAlmondAloe VeraAmbrosia CornAmerican BasswoodAmerican Beauty Dragon FruitAmerican BeechAmerican PersimmonAmethyst Falls WisteriaAmish Paste TomatoAnaheim PepperAnemoneAngelique TulipAngeloniaAniseAnise HyssopAnjou PearAnnabelle Smooth HydrangeaAnnual VincaApeldoorn TulipApple MintApril Tryst CamelliaArbequina OliveArizona Sun Blanket FlowerArkin CarambolaArmenian CucumberAroniaArp RosemaryArugulaAshwagandhaAsian PearAsian PersimmonAtemoyaAtlantic Giant Pumpkin🥕Atomic Red CarrotAucubaAugust Beauty GardeniaAunt Molly's Ground CherryAutumn Joy SedumAvocadoBachelor's ButtonBalsam FirBalsam PoplarBanana PepperBarbara Karst BougainvilleaBartlett PearBay LaurelBayberryBeach PlumBeauregard Sweet PotatoBecky Shasta DaisyBee Balm🍅Beefmaster TomatoBenarys Giant ZinniaBengal Tiger CannaBetter Boy Tomato🥬Bibb Lettuce🍅Big Beef TomatoBig Boy TomatoBilberryBing CherryBitter MelonBlack BeanBlack Beauty EggplantBlack Beauty ZucchiniBlack Beluga LentilBlack Cherry TomatoBlack CrowberryBlack Currant🍉Black Diamond WatermelonBlack Kabouli ChickpeaBlack Krim TomatoBlack RaspberryBlack Sapote🥬Black Seeded Simpson Lettuce🥕Black Spanish RadishBlack Tartarian CherryBlack WalnutBlack-Eyed PeaBlack-eyed Susan VineBlood OrangeBloomsdale SpinachBlue Bird DelphiniumBlue Bird Rose of SharonBlue FescueBlue Lake Green BeanBluecrop BlueberryBocking 14 ComfreyBok Choy

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.