Influence of take-all epidemics on winter wheat yield formation and yield loss

The effects of take-all epidemics on winter wheat yield formation were dete rmined, and disease-yield relationships were established to assess the agro nomic efficacy and economic benefits of control methods. Epidemics were gen erated in naturally infested fields by varying cropping season, crop order in the rotation, and experimental fungicide seed treatment. Disease inciden ce and severity were assessed from tillering to flowering. Yield components were measured at harvest. Models simulating the formation of the yield com ponents in the absence of limiting factors were used to estimate the losses caused by take-all. Losses were predicted by the disease level at a specif ic time or the area under the disease progress curve, reflecting accumulati on during a specific period. Losses of grain number per square meter and 1, 000-grain weight were linked to cumulative disease incidence between the be ginning of stem elongation and flowering, and disease incidence at midstem elongation, respectively. Yield losses were accounted for by both cumulativ e disease incidence between sowing and flowering, and disease incidence at midstem elongation. Results confirm the importance of nitrogen fertilizatio n in reducing the impact of take-all on wheat.