Septoria Tritici Blotch in Commercial Wheat Crops in England: The Use of Varietal Resistance in Disease Control

Variety choice is one of the key operational decisions a wheat farmer makes. A recent farm survey showed that farmers consider the disease resistance rating to be the primary factor when deciding which variety to grow. Here we analyse data from a survey of winter wheat crops between 1985 and 2019 in England to understand what factors affect the variety choice when faced with variety with different resistance ratings against Septoria tritici blotch, caused by Zymoseptoria tritici . We find that the mean Septoria tritici blotch resistance rating of the varieties grown showed considerable variations, with periods where the mean resistance rating decreased followed by periods with increased mean resistance rating. We explore the causes of these fluctuations and the factors that affect variety choice by the farmer. In this analysis we consider (i) the availability of variety with a preferred resistance rating, (ii) the long‐term Septoria tritici blotch disease pressure at the location of the farmers' farms, (iii) the availability of effective fungicides, (iv) whether farmers respond to a decrease in the resistance rating of a variety and (v) whether the Septoria tritici blotch severity in previous years affects the choice of the resistance rating of the variety in the subsequent year. The ultimate aim of this work is to understand the choices farmers make when selecting a wheat variety and how the choice of resistance rating is influenced by a range of aspects relating to the Septoria tritici blotch pathogen.