Armyworms are on the march. Not to exaggerate, but these small caterpillars are capable of destroying a lawn overnight by munching on grass blades.
They are present in small numbers most of the summer but when the weather conditions are right their population explodes in only a few days. Dry weather followed by a cool front and rain brought them on.
Armyworms have a white inverted Y on their head and are mainly green with brown or black stripes and only an inch long. In massive numbers they appear to march across a lawn or hay field destroying all of the grass.
I remember my Mother taking me out of school in Junior High for 2 days to help battle them in our main hay meadow. The devastation was unbelievable.
If you find them in significant numbers you need to act immediately. They will devastate a lawn or crop in a matter of hours. Spray with a pesticide that lists control of army worms. Use this in combination with a growth inhibitor that will kill unhatched worms.
They are most active in the cooler part of the day, so look for them in your lawn in the mornings.