Modelling Septoria Tritici Blotch (Septoria tritici) Disease-Yield Loss Relationship and Determining the Crop Growth Stag Provides Considerable Yield Return for Disease Management

Abstract

Septoria tritici blotch (Septoria tritici) (STB) is one of the important problems of wheat production in the Ethiopia; including Haddiya-Kambata areas of SNNPR. A field experiment was conducted at Hossana and Angecha in 2012 main cropping season to quantify the relationship between septoria tritici blotch and yield and yield components of bread wheat varieties. Three different spray intervals of propiconazole (Tilt 250 EC) and one unsprayed plot for each of the three varieties (Alidoro, Galama and Gambo) were used to create different STB epidemic levels. Treatments were arranged in randomized complete block design (RCBD) with factorial arrangement in three replications. Severity on all leaves (i.e. the leaves except flag leaf) and on flag leaf was recorded independently at weakly interval since the onset of disease. The respective host growth stage at the time of disease assessment was used to describe the weekly disease assessment included in the model, so that yield loss was associated with disease severity at particular plant growth stages. The F- statistics was used to test the significance of the overall relationship (p<0.05) and the coefficient of determination (R²) was computed to determine the proportion of the variation in yield loss explained by the disease variables (predictors) in the model. As the result this study, Yield and yield components negatively correlated with severity recorded on different plant growth stage at weekly intervals. On all tested varieties, STB developed after growth stage (GS) of 70 was strongly related with yield losses. After this growth stage, the grain yield loss of 12.35 to 23kg per hectare incurred for each of 1% increase of Septoria tritici blotch severity. Therefore, managing STB development before GS 70 provides better yield return.

Keywords: wheat, Septoria tritice blotch, severity, loss