Grass disappearing from under and around your trees?
We see this all the time. The turf under and around trees slowly disappears to nothing, leaving home owners wondering what is going on!
Bermuda has to have direct sunlight for healthy growth. That means 8+ hours per day, or it will struggle. While St. Augustine is more shade tolerant, it still needs a minimum of 4 hours of direct sunlight (and some additional filtered as well)
It doesn't happen over night, but if you don't trim the canopies of your trees up and keep them thinned out, you will eventually have no grass under or around your trees.
So get out there and trim your trees!