Effects of Self-sown Wheat on Levels of the Take-all Disease on Seedlings of Winter Wheat Grown in a Model System

Abstract The mechanisms of build-up of inoculum of the take-all fungus, Gaeumannomyces graminis var. tritici. and infection of crop plants from self-sown (volunteer) wheat were analysed in a factorial experiment in a glasshouse. Treatments comprised sowing-date, inoculum density, soil aeration and texture, volunteer density and control of volunteers. Timing of treatments was related to field practice by the use of cumulative day-degrees and by consideration of sowing date and the geometry of seed placement. Prior sowing of volunteers, which were exposed to soil inoculum. resulted in significant increases in the incidence and severity of disease on subsequently sown seedlings. Increasing the density of volunteer seedlings increased the levels of subsequent infection. This effect, however, was significantly influenced by sowing date and density of the initial inoculum. The use of glyphosate to kill volunteers did not markedly affect the carry-over of disease.