First and third authors: INRA, UMR BiO3P, Domaine de la Motte, BP 35327, 35653 Le Rheu Cedex, France; and second author: INRA, UMR Agronomie, BP 01, 78850 Thiverval-Grignon, France
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Accepted for publication 31 March 2001.
The effects of take-all epidemics on winter wheat yield formation were determined, and disease-yield relationships were established to assess the agronomic efficacy and economic benefits of control methods. Epidemics were generated in naturally infested fields by varying cropping season, crop order in the rotation, and experimental fungicide seed treatment. Disease incidence and severity were assessed from tillering to flowering. Yield components were measured at harvest. Models simulating the formation of the yield components 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 specific time or the area under the disease progress curve, reflecting accumulation during a specific period. Losses of grain number per square meter and 1,000-grain weight were linked to cumulative disease incidence between the beginning of stem elongation and flowering, and disease incidence at midstem elongation, respectively. Yield losses were accounted for by both cumulative disease incidence between sowing and flowering, and disease incidence at midstem elongation. Results confirm the importance of nitrogen fertilization in reducing the impact of take-all on wheat.
Gaeumannomyces graminis var. tritici
© 2001 The American Phytopathological Society