If clippings are composted, they should be mixed with other yard wastes or soil to aid in decomposition and reduce odors. Human, dog and cat feces should not be placed in compost piles because of the possibility of disease transmission. Meat scraps, bones, grease, whole eggs and dairy products also should not be added to compost piles because they can attract rodents. Diseased plant material or weeds that have gone to seed may be undesirable in a compost pile. No simple answer exists to this question.
Individual pesticides react in different ways and break down under unique conditions.
Research is being conducted to better evaluate the fate of pesticide products once applied to turf areas. Herbicides commonly used on home lawns persist in the soil from less than one month up to 12 months, depending on the chemical. If some treated clippings are mixed into a compost pile, they will decompose more rapidly in a properly maintained pile than in soil. In general, plant material in contact with insecticides registered for home use is safe to use in a compost pile. Insecticides sprayed on plant material break down rapidly in light, and the plant material usually can be used in the compost pile within one week of application.