Black Spots on Muscadines: Disease Identification Guide

Diagnosing Spot Diseases on Muscadine Grapes

Several fungal diseases cause black or dark spots on muscadine (Vitis rotundifolia) fruit and foliage. Without a lab test, visual diagnosis is tricky—but a good pictorial guide can narrow the possibilities.

Common Culprits

• Black rot (Guignardia bidwellii): Brown to black lesions on fruit, often with concentric rings; leaves show small reddish spots
• Bitter rot (Melanconium fuligineum): Sunken, dark spots on ripening fruit; salmon-colored spores in wet weather
• Ripe rot (Colletotrichum spp.): Circular, sunken lesions on mature fruit; pink/orange spore masses
• Macrospora spot: Small, dark spots with yellow halos on leaves and fruit

Next Steps

1. Compare symptoms to the UGA Muscadine Diseases guide (excellent photos).
2. Submit a sample to your county Extension office for definitive ID.
3. Practice sanitation: remove and destroy mummified fruit and fallen leaves.
4. Consider preventive fungicide sprays next season if disease was severe.