Whitewash Lichen

not listed

not listed

not listed

Whitewash Lichen is very common in Europe and North America. In the United States it occurs in the Pacific northwest and in the northeast from the East Coast to the Great Lakes region. It grows in very close contact with the substrate (crusticose) on the bark of oak and other deciduous trees, rarely on conifers, and rarely on rock. It neither harms nor benefits the tree.

The vegetative body may be thick or thin, small or large. It may appear as a small, well-defined patch with a distinct pale border, or as a large, irregular patch with diffuse pale edges, like a smear of paint. It consists of a central, vegetative portion containing both the algal and fungal partners (thallus), and a border with just the fungal partner (prothallus). The thallus is pale grayish-green or greenish white when fresh. It may be thin and smooth or thick, rough, and cracked. As it ages, the surface becomes gray and/or white, and it develops minute, pale green to bluish-green balls of cells (soredia). The soredia are fine, but they clump together forming coarse granules on the surface. When the thallus is thin the soredia are sparse. When the thallus is thick, the soredia are dense and cover the center. The structures that produce the soredia (soralia) are pale yellow to greenish-white, up to ⅜″in diameter, and usually have a raised rim. As the lichen ages, the soralia erode, leaving just raised lines.

The thallus is surrounded by by a white, felt-like, and often conspicuous prothallus. The prothallus often forms a conspicuous white border about ⅜″ wide.

Disk-like, spore-producing structures (apothecia) are extremely uncommon. When present, they are minute, 1 ⁄64″ to 3 ⁄64″ (0.2 to 0.4 mm) in diameter, gray to black, and flush with the surface of the thallus, sometimes hidden by it.

Common Button Lichen (Buellia stillingiana) apothecia are very common, more abundant, and larger.

Trees

Crusticose

Bark, rarely rock

Oak and other deciduous trees, rarely conifers

Sources

4, 24, 26, 29, 30, 77, 81.

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Location: Fairview Twp, Cass Co.

Location: Fairview Township, Cass County