Contribution to the population dynamics of Septoria nodorum in wheat crop systems
1989
Kaesbohrer, M. (Technische Univ. Muenchen, Weihenstephan f (Germany, F.R.). Lehrstuhl fuer Phytopathologie) | Hoffman, G.M.
(1) The population dynamics of Septoria nodorum in winter wheat crops (cv. 'Basalt', 'Kronjuwel') during three vegetation periods (1983-1985) were investigated in a typical disease region (Roggenstein, Kreis Fuerstenfeldbrueck, South Bavaria). The counts of pycnidia on different leaf insertions (F-9 to F = flag leaf) in the development stages EC 29 to EC 75 were used. (2) As parameters to characterize the population served: (1) percentage of leaves with pycnidia, (2) percentage of leaves with pycnidia after incubation, (3) intensity of pycnidia in the field (average number of pycnidia on different leaf insertions), (4) intensity of pycnidia total (average number of pycnidia on different leaf insertions after incubation). The data of 12 samples taken at weekly intervals were used to determine the infection- and propagation-periods in dependence on weather conditions (rainfall, temperature). (3) In 1983, the epidemic development was retarded till EC 49 due to low temperatures, in 1984 till EC 37 due to continuous dry spell. In 1985, a high percentage of attacked leaves was already reached in EC 30. The infection on higher leaves (F-1, F) and on the ears started from the inoculum mainly on F-3 and F-2. The severity of ear attack was not calculable from the pycnidia development on the leaves. Correlations between percentage of attacked leaves and number of pycnidia/leaf were observed in early stages of the epidemics. With high infection pressure (1985), the number of pycnidia/leaf remained below 10 within a range of 30 per cent attacked leaves. (4) Wheat-wheat crop systems were earlier and more frequently infected than wheat plants in a crop rotation under the same weather conditions. The probability for infections may be incomparably higher than in the rotation, especially with minimum tillage
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