My lawn is still recovering from the onslaught of chinch bugs last summer. Fertilization by Scotts Lawn Service, and some overseeding by me, have helped it recover. By last fall, it had greatly improved. There are still a few small patches that have yet to fill in completely but it’s looking much better than it did.
The area in the foreground (above ↑ photo) looked like this last September (below ↓ photo). I did not reseed this section. It only received fertilizer, so that illustrates the power of feeding to cause the bluegrass to grow new rhizomes for thickening the lawn.