Integrating Disease Control in Winter Wheat – Optimizing Fungicide Input

Winter wheat is one of the most commonly grown and important cereal crops in Europe. Fungicides are widely used in this crop to minimize yield losses from the attack of foliar diseases, primarily septoria leaf blotch (Septoria tritici), powdery mildew (Blumeria graminis) and rust diseases (Puccinia striiformis and P. triticina). The average yield in Danish wheat production is around 7.5 tonnes per ha and responses from disease control are today approximately 10% with a major variation (5-25%) caused by year, disease pressure and susceptibility of cultivars. Danish farmers have had a long tradition for minimizing and optimizing fungicide input in wheat based on several IPM (Integrated Pest Management) principles. Promotion of cultivars with good resistance, monitoring of disease development during the growing season, use of control thresholds and use of experiences from historical trial data along with a fast dissemination are important components in the Danish IPM strategy. Analysing historical trial data has shown that the highest net yield gain has been obtained from fungicide inputs at a TFI (treatment frequency index) between 0.4 and 0.75. The yield increase from fungicide usage was on average 3.2 dt/ha higher in susceptible cultivars than in resistant cultivars. The Danish fungicide input today is approximately 0.75 TFI per season and scope for further reduction is limited. The optimum fungicide input depends, however, on the grain price. A recent doubling of the grain price from 10 to 20 per dt will increase the TFI optimum by 50%. The difference between optimal fungicide input in resistant and susceptible cultivars is relatively small. However, the risk of reduced yield is considerably lower in resistant cultivars, compared to susceptible cultivars.