Disease control among plants

According to Derek Fell (2010, p. 84), the very best protection against the spread of diseases among plants, or against a disease reappearing in the next season, is to thoroughly clean up the garden in fall and winter.  After the first fall frost put dead stems in the compost pile or burn them. Many disease organisms will overwinter in leaf litter.  Turn over the soil and put down a thick layer of compost so beneficial bacteria can feed on diseased colonies.

Derek Fell. (2010). I'll make you a gardening wizard overnight! Lipenwald Publishers.