The effects of different nitrogen regimes on the epidemiological development of pathogens on winter wheat and their control
1992
Bueschbell, T. (Technische Univ. Muenchen, Freising-Weihenstephan (Germany). Lehrstuhl fuer Phytopathologie) | Hoffmann, G.M.
Two seasons (1985/86 and 1986/87) of field experiments examine the influence of cultivar (winter wheat: 'Apollo', 'Basalt') and nitrogen regime (80, 160 kg N/ha, 1985/86 -40, 80 and 160 kg N/ha, 1986/87) on the epidemiological development of the pathogens Pseudocercosporella spp., Erysiphe graminis and Septoria nodorum under natural conditions and from one location (Roggenstein, experimental station of the Technische Universitaet Muenchen-Weihenstephan). An extract of the results is shown in this paper. The actual infestation situation and the development of the pathogens have been determined for Pseudocercosporella using the Kaesbohrer-Klewitz-test (laboratory test, including taxonomic identification) between GS 22 and GS 32, and visual assessment of stem necrosis between GS 39 and GS 81 (1987) CGS 22 to GS 30 and GS 37 to GS 87, 1986). Erysiphe graminis infestation assessed weekly (GS 31-GS 75, 1986 - GS 32-GS 81, 1987) in marked plant rows in the field. Septoria nodorum assessed by the number of pycnidia and the number of latent between GS 11 and GS 87 (1986), and between GS 22 and GS 81 (1987). A calculation of values of infestation shows the curve of the actual state of disease. The effect of fungicide applications on the build-up of the populations of the pathogens was optimized by decisions thresholds. Based on the first threshold for powdery mildew, a second threshold has been formulated to take account of a more severe infestation pressure. It is triggered if, on leaves higher up the plant, an infestation severity of 1 % is exceeded, before GS 71. Fungicides modified the development of the diseases whose subsequent development was monitored by regular assessments, including measurement of yield. Both the aspects are discussed
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