Sweet Potato Diseases: How to Deal with Them

Sweet potatoes are one of those crops that give you a lot for a little effort. They’re tough, grow in all sorts of conditions, and reward you with delicious, nutritious tubers. But here’s the catch—like any plant, they’re not immune to diseases. And if you’re growing sweet potatoes, you need to be on the lookout for the usual troublemakers. So, let’s talk about sweet potato diseases—what they are, how to spot them, and what you can do to keep your plants happy. Grab your gardening gloves, and let’s dig in .

1. Sweet Potato Diseases: Black Rot (Ceratocystis fimbriata)

Sweet Potato Diseases: Black Rot

Ever pulled up a sweet potato and found black, sunken spots on it? That’s probably black rot, and it’s as nasty as it sounds.

How to Spot It:

  • Leaves turn yellow and wilt
  • Black, circular lesions on the tubers
  • A foul smell

How to Fight It:

  • Rotate crops don’t plant sweet potatoes in the same spot every year
  • Use certified disease-free slips don’t start with infected plants
  • Store harvested potatoes in a dry, well-ventilated place

Black rot can ruin a good harvest fast. Once it’s in your soil, it sticks around, so prevention is key .

2. Sweet Potato Diseases: Sweet Potato Scurf (Monilochaetes infuscans)

If you see purple to dark brown patches on your sweet potatoes, you might be dealing with scurf. The inside of the tuber stays fine, but let’s be honest—who wants to eat something that looks diseased?

How to Spot It:

  • Dark patches on the skin they look like dirt but won’t wash off
  • Plants look okay, but tubers are affected

How to Fight It:

  • Use clean, certified slips (infected cuttings spread this disease)
  • Rotate crops (again, don’t plant in the same spot every year)
  • Harvest carefully (rough handling can spread spores)

Scurf isn’t the worst disease, but it makes your harvest look unappealing, especially if you plan to sell your sweet potatoes.

3. Sweet Potato Diseases: Fusarium Wilt (Fusarium oxysporum f. sp. batatas)

This one’s sneaky. Fusarium wilt starts slowly and then suddenly—boom—your plants start yellowing and wilting.

How to Spot It:

  • Older leaves turn yellow and drop
  • Stems turn brown and dry up
  • Plants wilt even when watered

How to Fight It:

  • Choose resistant varieties some types of sweet potatoes can fight it off
  • Remove infected plants immediately don’t give the disease a chance to spread
  • Improve soil drainage this fungus loves damp conditions

Fusarium can stick around in the soil for years, so it’s one of those diseases you really don’t want.

4. Sweet Potato Diseases: Root Knot Nematodes (Meloidogyne spp.)

Sweet Potato Diseases: Root Knot Nematodes

Technically, these are tiny worms, not a disease. But they act like one by messing up your roots and making tubers lumpy and deformed.

How to Spot It:

  • Stunted growth
  • Wilting even when the soil is moist
  • Lumpy, distorted tubers with weird knots

How to Fight It:

  • Rotate Crops : getting tired of hearing this yet?
  • Plant Marigolds: They naturally repel nematodes
  • Use resistant sweet potato varieties

Root knot nematodes are sneaky because they live in the soil and slowly weaken your plants. If you’ve got them, you’ll notice your harvest getting worse over time.

5. Sweet Potato Diseases: Sweet Potato Mosaic Virus (SPMV)

Sweet Potato Diseases: Sweet Potato Mosaic Virus

If your sweet potato leaves are looking patchy, curled, and oddly yellow, it might be the dreaded mosaic virus.

How to Spot It:

  • Leaves have a weird mosaic-like pattern of yellow and green
  • Growth is stunted
  • Plants produce smaller, weaker tubers

How to Fight It:

  • Control aphids (they spread this virus like wildfire)
  • Use virus-free slips (infected planting material = guaranteed disaster)
  • Remove infected plants immediately

Unlike some other diseases, mosaic virus is spread by bugs, so keeping pests in check is your best defense.

6. Sweet Potato Diseases: Soft Rot (Rhizopus stolonifer & Other Bacteria/Fungi)

Soft Rot

Ever stored a perfectly good sweet potato, only to find it a few weeks later as a slimy, stinky mess? That’s soft rot, and it’s disgusting.

How to Spot It:

  • Soft, mushy spots on tubers
  • A bad smell like something died in your storage bin
  • Rot spreads rapidly in warm, humid conditions

How to Fight It:

  • Cure sweet potatoes properly before storage this toughens their skin
  • Humidity is your adversary when storing in a cool, dry environment.
  • Handle carefully bruises make them more vulnerable to rot

Soft rot is a storage nightmare. If one potato starts rotting, the rest aren’t far behind, so check your stored crops regularly.

Final Tips: Keeping Sweet Potatoes Healthy

Now that you know the main diseases, here’s a quick recap on keeping your sweet potatoes disease-free:

  • Start with clean, certified slips Don’t bring in trouble from the start
  • Rotate crops Don’t plant sweet potatoes in the same spot every year Improve drainage Many diseases thrive in wet soil
  • Control pests Aphids, nematodes, and other bugs spread disease
  • Store properly A well-cured and stored sweet potato is a happy one

Sweet potatoes are tough, but a little extra care goes a long way in preventing diseases. Keep an eye out, act fast if you see trouble, and you’ll enjoy a healthy, bountiful harvest .

References:

  • Clark, C. A., & Ferrin, D. M. (2018). Sweet Potato Diseases: Identification and Management. LSU AgCenter.
  • USDA Agricultural Research Service. (2022). Nematodes in Sweet Potato Crops.
  • University of California Integrated Pest Management Program. (2023). Sweet Potato Disease Prevention and Control.

Categorized in:

Horticulture, Urban Agriculture,

Last Update: February 3, 2025