Managing Soilborne Disease of Potatoes Using Ecologically Based Approaches

Soil fumigation and planting resistant cultivars remain the primary means for control of soilborne plant diseases. Fumigation however, is being constrained by increased costs, urbanization, and its negative environmental impacts. Resistance genes to soilborne pathogens are not available for many crop species. Using verticillium wilt as model disease we examined the potential of non chemical alternatives, specifically the use of organic amendments and green manures, as disease management tools. Application of organic products reduces disease incidence in controlled settings but its application in commercial use was hampered by inconsistent efficacy. Studies now have demonstrated that by-products of animal and plant production, such as meat and bone meal, feather meal, poultry and swine manure, soy meal, etc. can significantly reduce diseases but that the level of control obtained is product and soil specific. Three mechanisms of action for pathogen reduction were identified: 1) generation of toxic compounds such as ammonia and nitrous acid from high nitrogen-containing materials, 2) presence of volatile fatty acids (e. g. vinegar) and 3) alterations in biological agents that may suppress the activity of plant pathogens. For products that work mostly through the generation of active chemical ingredients, knowing the properties that regulate efficacy allows targeting their use to specific locations and thus, increased activity and consistency. Much less is known about how such materials influence rhizosphere residents involved in regulating plant health. New molecular technologies are being implemented to identify key players in maintaining root health. Through an understanding of the microbial soil ecosystem we should be able to develop disease control strategies that are more economical to growers and are more environmentally benign. © 2010 Potato Association of America.