Hi, 

This could white grub damage from either Japanese Beetles or the Green June Bugs.   You should notice a substantial amount of grubs when you dig in this area. Green June Bugs don't usually have this much damaged associated with them so it is more likely Japanese Beetles or Chafer bugs.

You can refer to our page on White Grub Management in lawns for how to treat and repair these areas. Bt is a decent method of control and many consider it safer than pesticides. July to early August is the appropriate time to apply it, so we are in the window for it. Since you are located in Montgomery County, you will need to abide by the counties pesticide laws for lawn care in your choices of what you use to treat them. The link lists approved products. 

You can then plan on aerating and overseeding these areas in the fall to re-establish the turf grass. 

Let us know if you have further questions. 

Emily