Mowing the grass too short can leave you with a stressed lawn and make it more susceptible to damage from insects and diseases. Keep your mowing height at 3 inches until the last cut of the season.
Make sure your mower blades are sharp. Ripped, shredded grass blades are more prone to disease and insect damage. Sharpen the lawnmower blades at the start of each season and check them during the season to make certain they remain sharp.