Bark miners are the larvae of flies, beetles, or moths that tunnel in the phloem and bark of maple, shadbush, cherry, ash, birch, holly, white pine, Douglas-fir, white fir, rose, and other trees and shrubs. Although sometimes called cambium miners, they do not tunnel in the cambium area as do the larvae of bark beetles, emerald ash borer, and bronze birch borer.
Damage typically appears as narrow, winding tunnels that are lighter or darker than the surrounding bark. These tunnels are 1/32 to 1/16 inch wide and are typically 6 to 12 inches long. They are noticed primarily in the thin bark of twigs, small branches, and the trunks of saplings. Because the tunnels are shallow and tend to wind lengthwise up the branch, they are unlikely to cause girdling or branch dieback, so control is not recommended.