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Root Rot

Root Rot

Phytophthora and Pythium species

Water moldalso: Phytophthora root rot, Crown rot, Root and crown rot

A group of soilborne water-mold diseases that rot the roots and crown of a plant, usually because the soil stays too wet. Unlike damping-off, which kills seedlings, root and crown rot strikes plants of any age, causing them to wilt, yellow, and decline as their root system dies underground. Poor drainage and overwatering are almost always behind it.

🔎 How to spot it

Above ground, look for plants that wilt, yellow or redden, grow slowly, stay stunted, and may drop leaves, often looking drought-stressed even in moist soil because the roots can no longer take up water. Below ground the roots and crown are soft, brown to black, and water-soaked instead of firm and white. Plants may collapse suddenly in warm weather after the roots fail.

🥀 Damage it causes

The water molds rot the fine roots and the crown, cutting off water and nutrient uptake, so the plant declines and often dies. It strikes vegetables, berries, and trees alike, and on woody plants a crown rot can girdle and kill an established plant over a season or two. Wet, heavy, poorly drained soil makes it far worse.

🔬 What causes it

Root and crown rot is caused mainly by the water molds Phytophthora and Pythium, which thrive in waterlogged soil. A full day or more of saturated soil lets them produce swimming spores that seek out and infect roots, so the disease follows overwatering, poor drainage, heavy clay, planting too deep, and low spots that stay wet. The pathogens persist in soil and infested plants.

🛡️ Prevent it

Good water management is the key: plant in well-drained soil or raised beds, do not overwater, and let the soil drain between waterings. Improve heavy soil with organic matter, set plants so the crown sits at or just above the soil line, and avoid low, soggy spots. Use clean, certified plants and reject any with dark, decayed roots.

🧯 If it is already here

There is no cure for badly rotted roots, so remove and destroy severely affected plants and correct the drainage before replanting. For a plant caught early, let the soil dry out and stop overwatering, which sometimes lets it recover. Replant in raised, well-drained beds or containers with fresh mix, since the pathogens linger in wet, infested ground.

💡 Good to know

Root and crown rot is usually a drainage problem wearing a disease costume, so the lasting fix is in the soil and the watering can rather than in a spray. It is easy to mistake for drought because both wilt the plant, but here the soil is wet and the roots are brown and mushy. Raised beds and restrained watering prevent most cases.

🌱 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.