My hibiscus tree bark and limbs are covered in a gray dead looking state. Do I spray it with something?

Question

When I scratch the limbs and trunk it is green underneath.

Answer 1

It sounds like you have powdery mildew, a common problem with hibiscus.
Here's a link to an article that will help:

https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-has-white-fungus.htm