By, the Old Guy with the Pony Tail
Lawn insects come in many shapes and sizes but basically, they either feed on the grass stems or the roots. Knowing who you are dealing with is critical in effective control. There are different products and different timings recommended for different insects. There are both preventative and curative products currently available.
Browning of the turf is a symptom of both surface feeding insects such as Chinch bugs and Sod webworms, and also root feeding insects such as grubs. The difference being, the damage caused by surface feeding insects tends to cause the turf blades to break off at the surface when briskly rubbed back and forth. Grub damage causes the turf to peel back like a rug.
In both circumstances, insect damage is sometimes misdiagnosed as drought damage. The lawn browns with lack of rain but only the healthy turf returns to green with the rain. The insect damaged turf remains brown.
In general, grub damage is most prevalent in the fall when grubs are small and voracious. Preventative treatment is typically recommended by June. A late May or early June treatment also suppresses many surface feeding insects. Curative treatment for grubs is recommended from early August up until soil temperatures start to drop in the late fall. At that time, grubs burrow deep in the soil below the frost line, returning to the surface in the spring. Damage in the spring is normally not as devastating to the lawn due to the fact that the grubs are much more developed and not as hungry as in the fall. In the spring, treatment is less effective because grubs are larger and less receptive to control products. In addition, the turf is much more resilient.