Question: In looking at the trunk of my peach tree I see a nasty crust adhering to it. The tree seems to be weaker. What causes it?

Answer: It’s probably a scale infestation. These insects are mobile for part of their lives, then they affix themselves to the trunks and limbs. Their effect on a tree is much as a tick outbreak is to animals. Control the scales with a horticultural oil spray during the dormant season. You can often use the same materials at different spraying strengths during the growing season. There are systemic insecticides that work on scale insects, but you’ll not want to use them while you have fruit on the tree.