Fungicide sensitivity in Tapesia yallundae populations collected from 15 wheat fields in the Western Cape province of South Africa

Abstract

In the Western Cape province of South Africa, eyespot disease (Tapesia yallundae) of wheat is primarily controlled by fungicide applications. Previous studies have shown, however, that isolates of T. yallundae vary in their response to fungicides. In the present study, 20 isolates from each of 15 fields with different fungicide histories were screened against carbendazim at 1 μg/ml; propiconazole, tebuconazole and flutriafol each at 0.1, 0.5, 1 and 2 μg/ml; and flusilazole and bromuconazole each at 0.05, 0.1, 0.5 μg/ml. No isolates were resistant to carbendazim. Flusilazole proved to be most effective of all the triazole fungicides tested. Based on the analysis of EC₅₀ values compared to that of a field at Gouda that is at baseline sensitivity, shifts in sensitivity were detected to all triazoles. This suggests that measures for prevention of build-up of resistance need to be employed.