TILLAGE SYSTEMS AND PLANT DISEASE

Abstract

The shift toward conservation tillage systems has caused plant pathologists to reexamine the importance of tillage and residue management on plant disease development. When plant diseases are influenced by tillage, it is often difficult to determine the factors responsible for changes in disease incidence or severity. One of the components altered by changes in tillage practices is the soil physical environment. Changes in soil physical properties may affect plant diseases by influencing the survival or activity of the pathogen, host susceptibility, or the prevalence of other soil microorganisms. Research is reviewed which illustrate how changes in the soil physical environment influence pathogen activity and disease development. Examples are drawn from tillage research, as well as research addressing the relationship of soil physical factors to disease development. Soil physical factors included are soil water, aeration, compaction, porosity, and temperature. Increased soil water can reduce disease through reducing plant water stress. Reduced soil aeration or temperature or increased soil water or compaction can predispose the host to infection and disease development. High soil water can also increase disease through increasing motility of the pathogen or diffusion of host exudates. Pore size may limit activity or movement of the pathogen. Changes in soil physical factors also may limit disease by affecting microbial antagonism. A greater understanding of how soil physical factors affect disease incidence and severity and pathogen survival and activity are needed before we can predict how the adoption of a tillage system will influence disease.