I have a varnish tree with a white powdery substance on the trunk. How do I get rid of it. Texas
Several different trees are commonly known as varnish tree: Toxicodendron vernicifluum, Aleurites moluccana, Koelreuteria paniculata, and Firmiana simplex among them. I'm guessing from your location that your tree is a Firmiana simplex, also commonly called Chinese parasol tree. This tree normally has few disease or insect problems, but it is susceptible to nectria canker, a fungal disease that could cause a white powdery substance to develop, and it also can get scale insects that may appear somewhat powdery. Without seeing the tree, it's difficult to tell exactly what the problem is. You might check with your local cooperative extension service office or a local nursery to see if they can identify the problem and provide suggestions for a remedy.