The question: I have a corkscrew hazel that is covered with some nasty-looking scale. Will the plant die? Should I spray it with horticultural oil?
The answer: It could be scale or it could be Eastern filbert blight, which produces scale-like lesions that feed on filberts; it goes in cycles and can spread by wind or rain. In either case, cut out all the affected areas and get the wood right out of the garden. (Don't bother to compost it. And make sure you clean your secateurs well afterward.) Then use a fungicide, applying it exactly as directed. .