I'd heard of this problem from golf course superintendents in India and the Philippines, but hadn't seen it myself until last month. The grass is bermudagrass, the location is Sri Lanka, and when we dug into the soil and broke the soil apart, we saw these insects, in the video below, scurrying about. Can you identify what caused the bare spots on this green?
When we took a cup cutter plug from the green, we found it full of these active insects.
These are termites. And they can be a recurring problem on some golf courses in tropical Asia. In fact, on some courses, termites are the major insect pest of putting greens.