Effect of foliar applied boron, manganese and zinc on tan spot in winter durum wheat

The effect of foliar application of boron, manganese and zinc on tan spot disease in winter durum wheat, caused by Drechslera tritici-repentis (Died.) Shoem., was investigated during a 2 years field study. Micronutrients were applied when plants were at the first node stage. In both years, in the sprayed plots the flag leaf had significantly fewer lesions than the untreated ones, at booting through milk stages. The treatment with B significantly reduced the number of lesions per leaf compared to the other treatments at booting stage in both years. There was no difference in the number of lesions per leaf between Mn and Zn treatments in the first year. In the second year, Zn treatment showed the lowest number of lesions at the booting and heading stage, whereas Mn treatment showed the lowest number of lesions at milk stage. There was a significant influence of Zn treatment on flag leaf area which might have negatively affected disease severity. In the case of Mn and B treatments there was no significant influence on flag leaf area. Moreover there was no significant difference in yield components. These findings suggest that foliar application of micronutrients can be used to reduce the severity of tan spot on wheat, however the physiological basis of this remains unknown.