Powdery orange golf balls (or larger spheres) have been spotted on pine trees across Minnesota. What are these strange growths? They are galls, a woody tumor like growth that is part plant, part fungus. In this case the pine trees have been infected with one of two different gall forming rust fungi: pine-pine rust (Endocronartium harknessii) or pine-oak rust (Cronartium quercuum). The diseases get their names from the trees they infect. Pine-pine rust only infects 2-3 needled pine trees like Jack pine, Scots pine and Ponderosa pine. Pine-Oak rust lives half of its life in galls on pine trees and the other half on the leaves of oaks like northern pin oak or bur oak. The galls are present year round. In the spring, both fungi release powdery yellowish orange spores, drawing attention to otherwise discrete brown woody galls.