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Influence of crop management on take-all development and disease cycles on winter wheat

Colbach, N., Lucas, P., Meynard, J.M.
Phytopathology 1997 v.87 no.1 pp. 26-32
Triticum aestivum, winter wheat, Gaeumannomyces graminis var. tritici, plant pathogenic fungi, roots, pathogenicity, measurement, crop management, developmental stages, cultural control, plant density, nitrogen, nutrient availability, statistical analysis, equations, disease control, plant diseases and disorders, sowing date, France
Wheat was assessed at four crop growth stages for take-all (Gaeumanomyces graminis var. tritici) in a series of field trials that studied the effects of five wheat management practices: sowing date, plant density nitrogen fertilizer dose and form, and removal/burial of cereal straw. An equation expressing disease level as a function of degree days was fitted to the observed disease levels. This equation was based on take-all epidemiology and depended on two parameters reflecting the importance of the primary and secondary infection cycles, respectively. Early sowing always increased disease frequency via primary infection cycle; its influence on the secondary cycle was variable. Primary infection and earliness of disease onset were increased by high density; however, at mid-season take-all was positively correlated to the root number per plant, which was itself negatively correlated to plant density. At late stages of development, neither plant density nor root number per plant had any influence on disease. A high nitrogen dose increased both take-all on seminal roots and severity of primary infection cycle but decreased take-all on nodal roots and secondary infection cycle. Ammonium (versus ammonium nitrate) fertilizer always decreased disease levels and infection cycles, whereas straw treatment (burial versus removal of straw from the previous cereal crop) had no influence.