In semi-field trials in spring wheat, azoxystrobin has shown a longer residual and preventive effect on Stagonospora nodorum than the triazole propiconazole. Three weeks after application, more than 90% control was still obtained with one quarter of the recommended rate of azoxystrobin. Propiconazole gave in comparison only 50% control. In another semi-field trial using Septoria tritici, azoxystrobin and propiconazole had a similar curative effect, both being significantly better than chlorothalonil. Different dosages (12-100% of normal rate of azoxystrobin) were tested in field trials. When taking into account the different timing, the most profitable dose has varied between 50 and 100% of normal rate, depending on growth stage and disease pressure. If optimal timing is used, 25-50% of normal rate has generally been sufficient. In 1998 in field trials azoxystrobin and the co-formulation propiconazole + fenpropimorph or tebuconazole provided similar control of S. tritici when applied after 4 or 8 days of precipitation, respectively. The test model for azoxystrobin recommended between 36 and 45% of the normal rates. Azoxystrobin gave an increase in yield of 100-600 kg ha -1 above the co-formulation or tebuconazole. So far azoxystrobin has shown profitable yields in all trials carried out in Denmark since 1994. However, it is still not known how many days of precipitation are required to make spraying with azoxystrobin profitable.

English

9910|AGRIS 0001

Jose Juan Caballero

CIMMYT Publications Collection