When a plant gets Leaf Spot Disease, the attacking fungus or bacteria creates small brown spots often trimmed in yellow where it is feeding on the leaves. These spots may vary in shape, color, and size. As with all other fungal and bacterial diseases, better air circulation, well-drained soil, dry leaves, and less water help control leaf spot disease on plants. Water only when 75% of the soil volume is dry and always discard excess water in the saucer after watering. Never mist a plant if leaf spot is suspected. Prune off any heavily affected leaves with clean snips and be sure to sterilize between each cut. Treat leaf spot with neem oil or a copper fungicide. Always follow the directions on the bottle.
If the spots look like mold or dirt and can be wiped off, then it’s most likely sooty mold. Sooty mold can often point to pests since it feeds on the sticky honeydew left behind as the insects feed on the plant. Rinse the plant with warm water outside or in the shower to knock off the majority of pests and rinse off the sooty mold. Use neem oil or insecticidal soap weekly until the pests are gone. Always follow the directions on the bottle. It might take several treatments to treat the infestation.