Sooty mold

Definition

A superficial, dark-colored fungal growth (various Ascomycota, commonly Cladosporium and Alternaria) that colonizes plant surfaces, fruits, and environmental substrates coated with sugary deposits. The fungus does not parasitize living plant tissue directly; rather, it exploits exogenous carbohydrates—either plant exudates or, more commonly in entomological contexts, honeydew deposited by sap-feeding Hemiptera such as aphids, scale insects, whiteflies, and mealybugs. Heavy infestations block photosynthesis, reduce fruit marketability, and serve as a visible indicator of underlying insect infestations. Sooty mold complexes are managed by controlling the insect vectors rather than targeting the fungus itself.

Etymology

Example

A citrus grove infested with California red scale (Aonidiella aurantii) develops conspicuous black coatings on leaves and fruit; the sooty mold layer, fed by scale honeydew, can downgrade harvest quality and prompt growers to monitor scale densities through the visible fungal signature.

Synonyms

• honeydew mold

Related Terms

• honeydew
• phloem feeder
• mutualism
• indirect damage
• Integrated Pest Management
• scale insect
• aphid
• whitefly

Usage Notes

The term describes a functional ecological syndrome rather than a single taxon; multiple fungal species may coexist on the same substrate. Specialists distinguish sooty mold from true plant pathogens by its epiphytic, non-invasive habit and its strict dependence on external carbon sources. In agricultural extension literature, 'sooty mold' often signals the need for insecticide or biological control applications targeting the honeydew producers. The spelling 'sooty mould' predominates in British English.