sugar gum trees
Asked July 23, 2018, 4:58 PM EDT
Noticed one month ago, bark on East side of three trees had white spots. now it is spreading up and down the bark. Just looks like bark being painted white.
Marion County Oregon
Your description of "Just looks like bark being painted white" suggests that the white material is lichen, an entirely normal substance on trees in the northwest. Lichen, also moss, both indicate we have good air quality. Lichen are simply using the bark as a surface to grow on. There's no reason to try to get rid of them.
We can be certain about this ID in several ways: Either send me a picture when you reply to this email, or compare what's on your tree with the images in this publication - Tree-Dwelling Lichens (https://njaes.rutgers.edu/fs1205/)
Lichens come in various colors and forms. Some appear to be painted on the surface whereas others are slightly raised and still others look downright leafy. It's likely you discover many examples on your next stroll through the neighborhood. Lichens may grow on bark, sidewalks, rocks, and boulders.