Diseases and insects harbor in decaying organic matter during their dormant cycle. Sanitation is a simple way to eliminate pest problems. Sanitation is especially important if you are trying to grow organically. If the foliage of your cool season vegetables or flowers is yellowing, you should prepare to discard them. Pulling the plants out, roots and all, is ideal.
Many pests harbor and feed on the portion below ground.
Your plant discards can be used to make compost. This is because in the composting process the materials heat up enough to kill harmful pests. This way you continue the cycle of life and build nice organic material that can be used to improve the soil in your planted areas. If you want to know what else to do in the landscape at this time, come out and see me at Art's Nursery, today. I'll be there from 10 a.m. to 2 p.m. to answer your questions and will be offering books that I have written as well.