Cleaning up your vegetable garden will help to reduce next year's disease and insect problems. In fact, good sanitation is one of the most important steps you can take to insure that next year's garden will be healthy.
Plant disease agents such as bacteria, fungi and viruses all remain alive, though dormant, during the winter months. By recognizing the places where these organisms hide, gardeners can often destroy them and prevent disease outbreaks the following spring. Many fungi spend the winter on or in old leaves, fruit and other garden refuse. These fungi often form spores or other reproductive structures that remain alive even after the host plant has died. Cucumber and squash vines, cabbages, and the dried remains of tomato and bean plants are all likely to harbor fungi if left in the garden over the winter.
Insects, too, survive quite nicely over the winter months. Cucumber beetle, Colorado potato beetle and Mexican bean beetle all overwinter as adults. In spring they migrate to young plants where they feed and lay eggs for a new generation. Insects and plant pathogens survive on weeds as well as on garden plants. Many weeds serve as alternate hosts for insects and fungi, helping them to complete their life cycle. Destruction of these weeds removes a source of future troubles.
To avoid any or all of the above problems, infested plant debris should be carefully raked up and disposed of in the trash. Do not put refuse on your compost pile. It takes a fair amount of heat to kill these organisms, and you won't want to recycle them right back into the garden.