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Sooty Mold

Sooty Mold

Capnodium and related fungi

Fungalalso: Sooty mould

A black, soot-like coating that grows on leaves, stems, and fruit wherever honeydew, the sticky waste of sap-sucking insects, has rained down. Sooty mold does not infect the plant; it grows on the honeydew, but a heavy black film blocks light and can weaken the plant. It is a sign that aphids, scale, whiteflies, or another honeydew maker are at work above.

🔎 How to spot it

Look for a dark gray to black, dry, sooty film coating the upper surfaces of leaves, twigs, and fruit, and often whatever sits below the plant. The coating wipes or flakes off, since it sits on the surface rather than penetrating. Above the blackened leaves you will usually find the real cause: colonies of aphids, soft scale, whiteflies, mealybugs, or psyllids, plus shiny, sticky honeydew and often ants.

🥀 Damage it causes

Sooty mold itself does not infect plant tissue, but a thick black coating blocks sunlight from the leaf, reducing photosynthesis and, when heavy, stunting growth and lowering vigor and fruit quality. Coated fruit is unsightly and downgraded. The bigger harm is usually from the sap-sucking insects producing the honeydew, not the mold itself.

🔬 What causes it

Sooty mold is caused by harmless fungi that grow only on honeydew, the sugary excretion of sap-feeding insects such as aphids, soft scales, whiteflies, mealybugs, and psyllids feeding above. Wherever those insects drip honeydew, the mold colonizes it. Ants make it worse by farming and protecting the honeydew producers from their natural enemies.

🛡️ Prevent it

Because the mold only grows on honeydew, the fix is to control the insects making it: keep aphids, scale, whiteflies, and mealybugs in check, and manage the ants that protect them so beneficial predators can work. Rinse honeydew off with a strong spray of water, avoid over-fertilizing with nitrogen, which fuels the soft growth those insects love, and encourage natural enemies.

🧯 If it is already here

Treat the insects, not the mold: knock back the aphids, scale, or whiteflies with a water jet, insecticidal soap, or horticultural oil, and band tree trunks or set bait to stop the ants. Once the honeydew stops, the existing sooty mold weathers and flakes off over time, and you can speed it up by washing the leaves and fruit with water or a mild soap solution.

💡 Good to know

Sooty mold is a symptom, not the disease, a black flag that a honeydew-producing insect is feeding overhead, so the real diagnosis is finding the aphids, scale, or whiteflies above the blackened leaves. Controlling those insects, and the ants that guard them, clears the mold; spraying fungicide on the mold itself accomplishes little.

🌱 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.