How about a photo of the "little centipede things"?

We need a proper ID before attempting to control.

Probably has 'SCAB" if the pecans don't mature and turn hard and black. It can be sprayed. Mine was a very large tree. I should have tried t have it trimmed first, but I decided to cut it down. It was too close to my house and had the problem for years. If I had had it trimmed extensively then sprayed for SCAB, it may have had a chance. I didn't know this until AFTER the fact. If you can check with an arborist or someone who trims trees who really knows pecans, get their opinion. Your county extension agent may know of arborist. Good Luck!