Fumagine is a noun that refers to a dark, sooty, or mold-like substance that develops on the leaves, stems, or fruit surfaces of plants, particularly trees. The word is derived from the French word "fumée," meaning smoke, due to its smoky appearance. It is also known as sooty mold.
Fumagine is a secondary effect caused by the presence of certain insects, such as aphids, whiteflies, or scales, which excrete a sticky sugary substance known as honeydew. This honeydew attracts fungi, specifically black or dark-colored ones, which then grow and form fumagine. The mold covers the plant parts affected by the honeydew, creating a black, powdery or greasy layer that can inhibit photosynthesis.
Although fumagine does not directly harm the plant, it can block sunlight from reaching the leaves, thereby reducing photosynthesis and affecting the plant's overall health. It is often seen on the undersides of leaves or on branches near the infestation of insects. Fumagine is more common in warmer and humid climates, where the growth and spread of fungi are more favorable.
To treat fumagine, it is necessary to control the underlying insect infestation that is causing the honeydew. This can be done by using insecticidal soaps or oils, or by introducing beneficial insects that prey on the pests. In some cases, physical removal of the insects may be necessary.
Preventive measures such as regular inspection, pruning of affected branches, and maintaining overall plant health can help reduce the occurrence of fumagine.
