Good lawn gone bad
What’s gotten to my lawn? It seems to be, it got ill, then invasive weeds came into the weakened soil. Is it a bug or fungus? Lawn had been good for years, but I have new lawn cutters this year.
We can't say for sure from the photo what is ailing your lawn.
Lawns need to be fertilized annually in the fall. Otherwise they slowly weaken.
Before you do so, take a soil test. (Search 'soil testing' on our website for how to do it and where to send it.) If the pH of the soil has dropped, it will need lime. Low pH soil weakens the turf.
Fall is also the best time to overseed and thicken up the lawn. Read this: http://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/lawn_pubs/HG102...
Many lawns have gotten fungal diseases this year because of the rainfall. Fertilizing in the spring exacerbates this. Overseed until the middle of October. .