Fall is an excellent time to start control efforts for next year's insect pest problems.
Many of our damaging pests will overwinter in fallen leaves or other refuse around the base of the plants. At the end of the growing season clean up the leaves and other organic matter and compost them at a different location. Properly composted organic matter will reach temperatures of 140-150o F. These high temperatures make it very difficult for many insect pests and weed seeds to survive.
Working (tilling or turning) the soil in the fall will also expose those insects that overwinter in the soil, such as grasshoppers, to dry air and cold temperatures and thereby reduce those pests. With fall tillage it is a good idea to work your previous season's compost into the soil for the next year. This will give the organic matter time to help improve the soil structure, which will help you grow healthier plants. Healthy plants are more resistant to insect damage.
One other thing that can be done this winter to help reduce insect pests is to spray your deciduous trees and shrubs with a dormant or horticultural oil. A winter spraying won't hurt, but the best-timed spray is in the early spring, just as the buds start swelling. There are a number of insect pests that overwinter under the bud scales and become exposed to the spray as the buds swell. Be sure to follow the label directions for plants and timing.