Last Resort
In its consumer booklet Citizen's Guide to Pest Control and Pesticide Safety, the EPA states that healthy lawns will have some weeds and insect pests as well as beneficial insects and earthworms. The guide notes that following a preventative health-care program for your lawn should enable you to avoid most pesticide use.

It's important to think of turf diseases and insect damage as symptoms of a breakdown in your lawn's ecosystem rather than as problems to attack with toxins. When problems occur, your first step should be diagnosis, followed by an adjustment of your cultural practices to alleviate the causes. If treatment becomes necessary, start with mechanical and biological controls. Synthetic chemical products should be a last resort. Use of synthetics will provide only temporary relief and, unlike botanical toxins, many synthetics remain potent in the environment long after their application. They can contaminate ground water and kill of needed soil microorganisms and beneficial insects.

If you feel that your lawn pest problem is so serious that it warrants the use of synthetic chemicals, try to use the least toxic products you can and those that break down relatively quickly. Also, check with your Cooperative Extension Service for local recommendations.