Rhytisma acerinum - Ритизма кленовая - Sycamore Tar Spot

Rhytisma acerinum - Ритизма кленовая - Sycamore Tar Spot - Ahorn-Tarzfleckenpilz 10/1/10—10/9/22

Rhytisma acerinum, commonly known as the Sycamore Tar Spot or Maple Tar Spot, is a fascinating species of fungi that belongs to the family Rhytismataceae within the Ascomycota phylum. This fungus is widely distributed across Europe and North America and primarily infects the leaves of sycamore (Acer pseudoplatanus) and other maple species (Acer spp.). The fruiting bodies of Rhytisma acerinum, known as apothecia, appear as distinctive black, tar-like spots on the surface of infected leaves. These spots typically measure 5 to 20 mm in diameter and are surrounded by a yellowish halo. The fungus overwinters on fallen leaves, releasing spores during the following spring to infect new leaves. The asci of Rhytisma acerinum contain eight spores each, which is a characteristic feature of the Ascomycota phylum. The spores are needle-shaped and measure approximately 45-90 x 1-2 µm. They are hyaline, rendering them almost transparent, and often appear in clusters. Rhytisma acerinum is considered a plant pathogen, causing a condition known as tar spot disease in maple and sycamore trees. While the disease can lead to premature leaf drop and reduced photosynthesis, it rarely causes significant harm to the overall health of the tree. In some cases, however, severe infections may result in reduced growth or defoliation. Since Rhytisma acerinum is a plant pathogen and not a mushroom-forming fungus, it is not edible. Its primary importance lies in its impact on the health of sycamore and maple trees and its potential as a subject of study for plant pathologists, mycologists, and naturalists. To control the spread of tar spot disease, it is recommended to collect and dispose of infected leaves during the fall season. This helps to reduce the source of inoculum and limit the spread of the fungus to new leaves in the following year. Fungicides are generally not recommended, as tar spot disease is usually not severe enough to warrant their use.