I have a grayish white foam (not powdery mildew, but something else) growing around the base of one of my squash plants. It is the consistency of butter. Do I need to be concerned about it spreading or harming the plants? The plant involved (one of a dozen) is beginning to bear and it looks to be healthy and plentiful.
This is a fungus. It will not harm anything unless it is ingested. Usually it is more yellow than gray. Have you put new mulch down recently? It usually surfaces with that.