Thank you for contacting Delaware Cooperative Extension. You may receive a short survey after the answer to this question.
Without seeing a sample of your lawn turfgrass, it is impossible to tell what the problem might be. You may take a sample in to your local County Cooperative Extension office. A good sample for turf includes grass blades, roots, and soil, and a margin showing healthy to diseased, or good to poor. A small container such as a soft butter tub or left-over storage container work well for this.
You do not want to use an insecticide if you are not sure that insect pests are a problem. Pesticides are expensive, very specific, and we all need to be careful to apply them according to the label and disposal instructions.
There are some general guidelines that may help you with your lawn. Water one a week during times of drought. Deep watering is best. Frequent watering from a sprinkler system may encourage disease. Do not water late in the day, as water on the leaves promotes disease. Do not over-fertilize, but fertilize once a year in the fall.
Good luck with your lawn.