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Southern Blight

Southern Blight

Sclerotium rolfsii

Fungalalso: Southern stem rot, Sclerotium rot

A warm-climate fungal disease that rots plants at the soil line and wilts them suddenly, leaving a fan of white mold and seed-like tan sclerotia at the base. Southern blight hits a huge range of vegetables in hot, humid weather and can kill a healthy plant within days once it girdles the stem.

🔎 How to spot it

Look for sudden, permanent wilting of an otherwise healthy plant, with a dark, water-soaked rot girdling the stem right at the soil line. The giveaway is a fan of coarse white mold spreading over the lower stem and the nearby soil, studded within a few days with round tan to reddish-brown sclerotia the size of mustard seeds. Leaves yellow and the plant collapses.

🥀 Damage it causes

By girdling the stem at the base the fungus cuts off the plant, causing rapid wilt and death, often just as it reaches size. It rots crowns, lower stems, roots, and fruit lying on the soil, and can move down a row plant to plant. In warm regions it can take out a substantial share of susceptible crops.

🔬 What causes it

Southern blight is caused by the soil fungus Sclerotium rolfsii, which survives in soil and debris as tough sclerotia for years. The sclerotia sprout in warm, moist conditions and the fungus attacks the stem base, helped along by crop debris and organic mulch in contact with the stem. It is favored by hot weather, 80 to 95 F, moist soil, and acidic conditions.

🛡️ Prevent it

Rotate away from susceptible crops and bury crop debris deeply by tilling, since the fungus needs surface debris and sclerotia near the soil line. Keep mulch and trash pulled back from the base of stems, improve drainage, and avoid the dense, moist conditions it loves. Solarizing the soil in hot climates and deep burial both lower the sclerotia in the topsoil.

🧯 If it is already here

There is no rescue for a girdled plant, so remove infected plants along with the surrounding sclerotia, taking out the nearby soil to about three inches deep and a foot beyond the spot, and do not compost any of it. Because the fungus lives in the soil, the lasting controls are rotation, deep burial of debris, and sanitation rather than sprays.

💡 Good to know

The white fan of mold and the scatter of mustard-seed-sized tan sclerotia at the stem base are unmistakable and separate southern blight from other wilts. It is mainly a problem of hot, humid regions and summers. Because the sclerotia persist in soil for years, keeping debris and mulch off the stem base and rotating crops are the practical defenses.

🌱 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.