Q: I have dark black deposits on the bark of a red maple tree.
A: It could be an indication that the trees are infested with gloomy scale. The maple trunk gradually turns black as sooty mold accumulates on the honeydew that the scale insects produce. Gloomy scales often go undetected for years due to their size. They’re about the size of a pin head (1/16 to 1/8 of an inch) and look like very small bumps on the bark of the tree. Although they blend into the bark very well, they’re easy to identify by gently scratching the bark with a fingernail, causing them to flake off. If you decide your trees need treatment, apply horticultural oil during the dormant season and again in early summer. If control is successful, the black patches will fade away