Control of Septoria tritici based on ELISA-thresholds

In Europe Septoria tritici (ST) is actually one of the most important diseases in wheat. The data from 12 Swiss field trials from 1993 to 1998 with different cultivars were analyzed. In 1/3 out of the cases a treatment against ST was economically justified. This situation is an ideal prerequisite to use intervention thresholds. From growth stage (GS) 32 to 65 we measured ST on the leaves F-4 to F (flag) with an ELISA kit. The antigen data were correlated with the visually assessed disease severities in GS 83. A strong relation to the disease state in GS 83 was measured with ST antigen data of the leaves F-3 at GS 39-45 and F-2 at GS 55-59. Using 1 (GS 39-45) and 5 (GS 55-59) antigen units as threshold values, in 85 and 93% of the 47 respectivelly 42 cases an economically right spray decision would have been taken.