Taxonomic position: Domain: Eukaryota; Kingdom: Fungi Phylum: Ascomycota; Class: Ascomycetes; Subclass: Leotiomycetidae; Order: Helotiales; Family: Dermateaceae
Description: M. salicicola appears on the abaxial side of the leaf as purplish stains of a diameter of about one millimeter. The central area becomes lighter in color until it turns silvery white. The acervuli develop on this lighter area. Dark purplish lines irregularly surround the stains. To the naked eye, the acervuli look like small white dots scattered on the stains. They may also occur as one very visible single dot which on the central area of the stain.
M. salicicola produces stains of varying colors (gray to reddish brown) in the twigs and branches of white willow, as well as in the petioles of weeping willow, white willow and hybrid willow.
Penetration by M. salicicola is direct, and the infection is localized. How long the incubation period takes will depend on the affected organ and the temperature. During the vegetative period, propagation is by means of conidia carried by wind and rainfall. Year after year, hibernation occurs probably in cankers formed in twigs and branches. The ascosporic form may also be significant at the onset of the infection, which occurs in the spring. M. salicicola also produces premature defoliation in willows, and this affects the diametrical growth of the wood.
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