Effect of septoria leaf spot in spring wheat

Abstract

A natural infection of Septoria tritici first appeared in an ‘Aotea’ wheat trial at tillering (G.S.3), when the disease occupied 10% of the third-leaf area. Fungicide sprays applied at tillering reduced the severity of the disease for up to 6 weeks. Application of mancozeb or benomyl at ear emergence (G.S.10.1) reduced infection on the flag leaf and leaf 2 by 10-20%, and increased the persistence of green leaf tissue. A yield increase of 14% and 17% over that of the unsprayed plots was achieved, but this increase was not significant under the experimental conditions. The increased yields were due to a significant increase in 1000-grain weight.