A comparative study into the effects of strobilurin containing and azole fungicides on the content of deoxynivalenol (DON) in wheat samples of 1999. Initial results.

摘要

Field trials were conducted in the 1999 season at 13 locations within Germany to determine the effects of strobilurin containing fungicides (both products which only contained a strobilurin as well as combination products with azoles) compared withazole solo products on the deoxynivalenol [vomitoxin] (DON) content of wheat samples following inoculation of plants with Fusarium graminearum [Gibberella zeae] and F. culmorum. In general, this season was characterized by notably lower DON contents thanin the previous season. The 1999 median of 0.3 mg/kg (n=96 samples from untreated, control plots) is clearly well below the currently proposed maximum tolerated DON level of 1 mg/kg. In contrast to this, the median value in 1998 was 1.5 mg DON/kg (n=124samples from untreated, control plots). The results indicate that both the location as well as the prevailing weather conditions have a significant influence on the degree of toxin contamination. A fungicide application, irrespective of the type of active ingredient and also independent of the level of toxin contamination, resulted in a significant reduction in the level of DON (officials trials, as well as the trial series A & B). The degree of toxin reduction following treatment with strobilurin 2 was always weaker than either strobilurin 1 (which had a similar effect to the azole fungicides) or the other fungicides used. This indicates, that strobilurin fungicides can be clearly differentiated. Furthermore, it was shown that the effectiveness of afungicide in reducing the DON level was strongly dependant on the time of its application. In this report, the strobilurin containing fungicides (mixtures 1 & 3) were comparable to azole 1 within the application period "beginning of flowering" to "end offlowering". The optimal application times in the 1999 season were "full flower" and "end of flowering".