ABSTRACT The severity of epidemics of Septoria tritici blotch (STB; caused by the fungus Zymoseptoria tritici ) in winter wheat ( Triticum aestivum ) in England has been analysed using a long‐term data set arising from the Defra‐funded pest and disease survey, with the analysis focussing on whether the variables that affect disease severity under controlled experimental conditions also affect disease severity in commercial crops. Farmers in England generally have control over (i) the variety grown, (ii) the efficacy of fungicide programme, (iii) the sowing date, (iv) seed origin, (v) cultivation history and (vi) cropping history. Varietal disease resistance, fungicides and sowing date had a significant correlation with disease severity. A significant interaction was observed between varietal resistance and the efficacy of the fungicide treatment programme. Different combinations of varietal resistance and fungicides can lead to a particular disease level. Similar interactions were also observed between varietal selection and sowing date, as well as sowing date and fungicide treatment programme. However, farmers did not appear to optimise these interactions, with only fungicide programme predicted efficacy being adjusted with sowing date. A contrast between the disease management decisions by farmers in the East versus the West of England was observed, with less effective fungicide treatment programmes being used in the West compared to the East, and varietal resistance to STB higher in the West than in the East.
Bosch et al. (Fri,) studied this question.