Plant Problem Diagnosis Key / Diseases
Disease
Sooty mold
Capnodium and related fungi
Black fungi that grow on honeydew, not on the leaf itself. They block light but do not infect; the real problem is the sap-feeding insect above.
Signs
- Black film that wipes or peels off, leaving green leaf below.
- Sticky leaves underneath the coating.
- Aphids, whiteflies, scale or mealybugs on the leaves or branches above.
What favors it
Honeydew from aphids, whiteflies, soft scale and mealybugs.
Prevention
- Control the sap-feeding insects that produce honeydew.
- Control ants that guard those insects.
Often confused with
Sources
- Honeydew and Sooty MoldUniversity of Maryland Extension
- Sooty MoldsNC State Extension
Treatment by crop
Cultural, biological and chemical options in the order to use them, and notes written for each crop.
Identification is free. Treatment is on the Home and Pro plans.
Questions in the key that lead here
- Look the plant over, leaf undersides included. Are insects, mites, slugs, eggs, webbing or droppings on it?
No, only damage or discoloration - Where is the problem?
Leaves - What does the leaf damage look like?
A coating or growth on the surface - What is the coating like?
Black sooty film over a sticky surface
Not a match? Start the key or describe what you see.
More photos
More from university Extension: search Extension pages on sooty mold, or find a plant diagnostic lab through your state's Extension.
Other diseases
- Anthracnose
- Apple scab
- Bacterial leaf scorch
- Bacterial leaf spot
- Bacterial wetwood (slime flux)
- Bacterial wilt of cucurbits
- Black knot
- Black spot of rose
- Bleeding canker
- Boxwood blight
- Canker diseases
- Cedar-apple and related rusts
- Crown gall
- Damping-off
- Downy mildew
- Dutch elm disease
- Early blight and Alternaria leaf spot
- Elm yellows (phloem necrosis)
- Fire blight
- Fusarium wilt
- Gray mold (Botrytis)
- Late blight
- Mosaic viruses
- Needle cast and tip blight
- Oak wilt
- Powdery mildew
- Root and butt rot
- Root rot (Pythium and Phytophthora)
- Rust
- Septoria leaf spot
- Shade tree anthracnose
- Tar spot of maple
- Tomato spotted wilt and impatiens necrotic spot viruses
- Verticillium wilt
- White mold (Sclerotinia)
- White pine blister rust