Long-term monitoring experiment in wheat on the sensitivity of Pseudocercosporella herpotrichoides and Septoria nodorum for DMI-fungicides: first results
1989
Fehrmann, H. (Goettingen Univ. (Germany, F.R.). Inst. fuer Pflanzenpathologie und Pflanzenschutz) | Berndt, H. | Manns, G.
Results are reported from the 1987 and 1988 seasons of a long-term field experiment since 1984 monitoring prochloraz sensitivity of the eyespot fungus (Pseudocercosporella herpotrichoides) in wheat. In a number of 200 square meters plots (25 m distant from each other, surrounded by barley), Sportak Alpha (prochloraz + carbendazim) were applied in different spray schedules, other spraying programmmes remaining without DMI fungicide. Laboratory surveys of wheat haulm-base material showed only very minor shifts towards lower prochloraz sensitivity, being without importance for fungicide efficacy in the field. In two pot experiments, at 1 ppm in vitro prochloraz insensitive strains of P. herpotrichoides proved to be somewhat less pathogenic to wheat than strains freshly isolated from agar medium with 1 ppm prochloraz present. A lower pathogenicity of less prochloraz sensitive strains means a lower competitiveness of the latter in natural populations of the fungus. Preliminary investigations on the sensitivity of Septoria nodorum against propiconazol were carried out in a similar way. Following three DMI applications (prochloraz or propiconazol) per season for several years, a very small, but statistically insignificant shift towards lower DMI sensitivity was observed, as compared with material from plots without a DMI history
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