Plant care guide
Rubber Plant Fungal Infection: Anthracnose and Leaf Spot
Updated
Does my Rubber plant have a fungal infection?
Fungal leaf disease is uncommon on rubber plants indoors, but anthracnose, Myrothecium leaf spot and Botrytis blight do occur on Ficus elastica. Wet leaves, wounds and humid, still air favour them; cold injury and bacterial spots can look similar.
What to do first
Remove spotted leaves with clean tools, stop misting or wetting the foliage, and improve air movement. Use a labelled fungicide only after removing infected leaves, and only if new spots keep appearing.
Fungal disease is not the usual reason a rubber plant looks unwell indoors. Clemson HGIC’s rubber plant factsheet says plant diseases are very rarely a problem in the home. Penn State Extension explains that foliage plant diseases generally begin during production. Indoors, the air is usually too dry for them to keep spreading unless the leaves are kept wet.
They do happen, though. The University of Florida’s Ficus disease guide describes several fungal diseases on Ficus elastica. Most trace back to wet foliage, wounds or humid, still air.
Fungal diseases seen on rubber plants
| Disease | What it looks like on Ficus elastica | Favoured by |
|---|---|---|
| Anthracnose (Colletotrichum, Glomerella) | Dead spots that turn dark brown; in humid air, brown spore masses form concentric rings; leaves may fall | Wet, humid conditions; tissue damaged by misused sprays |
| Myrothecium leaf spot | Round, coin-sized brown lesions with black spore structures in rings | Warm, humid conditions; entry through handling wounds |
| Botrytis blight (grey mould) | Young leaves and stems turn brown to black with brown fuzz | Cool, damp conditions, especially on cuttings |
| General fungal leaf spot | Small brown spots with yellowish margins, sometimes target-like, with tiny black dots | Splashed water, poor air circulation |
The first three come from the UF guide. The last row is Clemson’s description of fungal leaf spots on houseplants.
UF notes that variegated rubber plants are commonly infected by anthracnose. The white parts of the leaf lack chlorophyll and are weak and very susceptible. Penn State describes anthracnose spots on Ficus as greasy-looking, then yellow, then dead, with a yellow halo.
Rule out look-alikes before you treat
A brown spot on its own does not prove a fungus. Check for these first:
- Bacterial leaf spot. UF describes Pseudomonas leaf spot on Ficus elastica as circular, water-soaked lesions. Clemson adds that bacterial spots may have a yellow halo or a sticky ooze. Fungicides aimed at fungi will not fix it.
- Cold injury. Penn State links large brown blotches on mature leaves, and puckered brown young leaves, to temperatures below 4 °C (40 °F).
- Oedema. Corky bumps on leaf undersides point to excess soil moisture with poor light, not infection. See our rubber plant edema guide.
- Root trouble. Yellowing with leaf drop in wet mix points to the roots first. Clemson links yellowing to soil that stays too wet.
Our rubber plant brown spots guide and pattern-based brown spot guide help sort spots by location and texture.
Stop the spread
- Remove spotted leaves with clean, sharp pruners. Clemson advises picking off and destroying infected leaves. UF notes that removing infected tissue lowers the number of spores.
- Wear gloves. Clemson notes that rubber plant sap may irritate skin.
- Stop misting. Clemson’s anthracnose advice is plain: do not mist leaves.
- Water the mix, not the plant. Penn State recommends watering in a way that keeps water off the leaves. Clemson warns that splashing spreads leaf-spot fungi.
- Improve air circulation. Clemson lists good air movement among the prevention steps for fungal leaf spots.
- Avoid wounds. UF says Myrothecium infects mainly through handling wounds, and Clemson notes that wounding helps anthracnose fungi enter. Wipe dust off gently with a damp cloth, as NC State suggests, instead of scrubbing.
- Clean up fallen leaves. Clemson notes that leaf-spot fungi survive on dead plant matter.
Should you use a fungicide?
Start with cleanup and drier leaves. If new spots keep appearing on new leaves, Clemson lists copper soap, chlorothalonil, myclobutanil and tebuconazole for anthracnose on houseplants, used after removing infected parts.
Follow the label for the product you choose, including the plants it covers. Clemson suggests spraying houseplants outdoors in the shade during mild weather, then bringing them in once dry. UF lists other fungicides for Ficus, but its guide is written for commercial greenhouse growers.
UF also notes that anthracnose often follows tissue damage from misused pesticides. Do not spray repeatedly as a precaution.
Judge recovery by new leaves
Existing spots will not fade. Recovery means the spots stop spreading and new leaves come in clean.
If spots keep spreading after cleanup and drier leaves, send a sample to your local extension plant diagnostic service. Fungal and bacterial spots can be hard to tell apart by eye.
For everyday care, see our rubber plant care guide. The rubber plant hub collects our other Ficus elastica pages.
References
- University of Florida IFAS EDIS PP308: Ornamental Ficus Diseases: Identification and Control in Commercial Greenhouse Operations
- Penn State Extension: Ficus Diseases
- Clemson Cooperative Extension HGIC 2251: Houseplant Diseases & Disorders
- Clemson Cooperative Extension HGIC 1510: Rubber Plant
- NC State Extension Gardener Plant Toolbox: Ficus elastica
How this guide was put together: University of Florida IFAS, Penn State Extension, Clemson HGIC and NC State Extension guidance.