Why the areoles of my cactus are becoming black? What is this fungi developping there?
The fumagine come from fungi belonging to several species: Capnodium meridionale, Capnodium oleae, Ceratocarpia cactorum… etc. These fungi proliferates from the sugars contained in the honeydews of insects: Cicadelles, Aleurodes, Plant louses and other mealy bugs. In the case of Ferocactus, Thelocactus and some others, the plants themselves produce this honeydew by the glands on the areoles and sometimes confused with very young floral buttons. To develop, the fumagine needs favorable climatic conditions: soft temperatures and moisture. The fumagine does not attack the plants, it does not penetrate inside its skin. But in great quantity it blocks the light, preventing photosynthesis and gaseous exchange. Moreover, it gives a disgusting aspect. To remove it, There is no miracle solution and it will be necessary to start again the following year. One can clean the plant with a small brush and a deterging product containing a little bleach. Tke care to rinse a lot. To avoid such problem
