The term fumaggine refers to a group of saprophytic fungi, which do not attack the plant, but which feed on sticky substances (honeydew) that are produced by various insects, such as cochineal aphid and metcalfa.
It has dark and sooty structures, which are composed of intertwined mycelia. The more these filaments are compact and numerous, the more the plant is deprived of the light necessary to live. With prolonged attacks the plant, after a long period of weakening, can lead to death. There are different types of fumaggini: from dry and crusty ones to softer and greasy ones. This fungus generally has a blackish brown color, which also gives the attached plant an unpleasant aesthetic appearance.
Fumaggine - fumaggine plants">Causes of smokiness
The main causes of the formation of smokiness are poor ventilation, the presence of honeydew and a fairly high degree of humidity. Some types of fungus, however, do not require high humidity, since they proliferate easily even in very dry climates. The main genera of mycelia responsible for this disease are: Capnodium, Antennaria, Cladosporum.
For an effective fight it is first necessary to eliminate the cause of this disease, the honeydew, which is produced in most cases by aphids and scale insects. The use of specific products against these parasites usually causes the elimination of saprophytic fungi after a short time. It is rare to intervene on the mycelia of fumaggine, unless the state of infection is not really advanced and widespread: the best products in this case are those based on copper. Mechanical interventions can also be carried out to remove the blackish mold from the leaves; in this case it is very important to fight at the same time the aphids and the scale insects, if still present, to avoid the reappearance.
Smokiness on citrus fruits
As explained previously, fumaggine is a fungal disease that proliferates in poorly ventilated and hot humid environments even if some strains of fungi attack and proliferate without many problems even in hot and dry climates. Very often, especially in central and northern Italy, the presence of fumaggine on citrus fruits is frequently found and this association is soon revealed.
Citrus fruits grown in pots, at these latitudes, are often taken to greenhouses during the winter to protect them from the cold and possible frosts. Where they are not taken to greenhouses they are in any case covered most of the time with protective sheets. Greenhouse cultivation, a warm humid environment where in the winter months there is often no adequate air recirculation, can often lead to plants being attacked by aphids and consequently by smokiness.
If you have citrus plants attacked by this fungus, do not worry and intervene as if it were a normal houseplant, first trying to eradicate the presence of aphids and then physically remove the fumaggini from the attached leaves, using for example wet cotton. .