Sooty mold
/ˈsʊti moʊld/
Definition
Sooty mold refers to a dark, soot-like coating of fungi that grows on sugary honeydew left by sap-feeding insects such as aphids, scale, and whiteflies. It forms on leaf, stem, and fruit surfaces rather than inside plant tissue, which distinguishes it from many true plant diseases. The coating can block light and reduce photosynthesis, but it is usually a secondary problem linked to insect activity, not direct infection of the plant.
Effects on Plants
- Light-blocking coating: On leaves, sooty mold can reduce light reaching the surface, which may lower photosynthesis, the process plants use to make sugars from light.
- Signal of sap-feeding pests: Its presence often points to honeydew-producing insects such as aphids, scale insects, whiteflies, or mealybugs, so the coating can be a useful clue during plant inspection.
- Mostly a surface problem: It usually sits on the outside of leaves, stems, and fruit rather than invading plant tissues, but heavy buildup can still weaken appearance and vigor over time.
- Management depends on the cause: Cleaning affected surfaces helps appearance, but lasting control usually comes from reducing the insects that leave honeydew, especially in still, humid growing conditions.
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