Control strategies for stubble-borne pathogens of wheat

Stubble-borne pathogens of wheat are becoming increasingly more important as fanning practices change, leaving increasing amounts of crop residues on the soil surface. Chemicals, biocontrol, resistance, and cultural practices are the four main strategies scientists have studied to help control these pathogens. Foliar-applied chemicals have not been widely used; however, they may become more attractive as stubble-borne foliar pathogens increase. New seed-treatment chemistry holds promise for controlling root diseases such as take-all. Additionally, systemic seed-treatment fungicides have the potential to delay epidemics of residue-borne foliar pathogens. Biocontrol of take-all by fluorescent pseudomonads and of Pyrenophora tritici-repentis using the fungus Limonomyces has been demonstrated, however, additional research is needed on the ecology of residues and ways to manipulate biocontrol agents. Useful levels of resistance to cephalosporium stripe, tan spot, septoria tritici blotch, and stagonospora nodorum blotch are available, have been deployed to some degree, and provide excellent control. Nevertheless, not all cultivars have high resistance and there is need for continued work in this area. Tillage practices that destroy residue, such as burning and plowing, are effective against diseases such as tan spot; however, the trend is toward more reduced- or no-till farming. Reduced tillage should be coupled with crop rotation which negatively affects many wheat pests including the diseases tan spot and take-all. In summary, all main control strategies hold promise to help manage residue-borne pathogens.