A model to predict the risk infection of Gibberella zeae ascospores

Fusarium Head Blight (FHB) is caused by a species complex of Fusarium and Microdochium. This disease, common in wheat, can induce losses of yield but also degrade safety quality of grains. Indeed, the most common species of Fusarium in France is Fusarium graminearum (teleomorph=Gibberella zeae) and it can produce toxins, in particular deoxynivalenol (DON) regulated by the European Commission for cereals intended for human consumption. In France, the presence of DON in wheat is clearly linked to crop debris remaining on soil at flowering stage. Crop debris is usually colonized by F. graminearum which can produce sexual fruiting bodies named perithecia. Those perithecia release ascospores under specific environmental conditions which are assumed to be the major part of inoculum for wheat infection. The objective of this work was to develop a model to predict ascospore risk. The model was developed following a mechanistic approach where the sexual stage of G. zeae was divided in 5 stages: perithecia formation and maturation, ascospore maturation, discharge and germination. For each stage, a specific equation was developed using weather variables (rain, relative humidity, temperature) from literature as independent variables. The final model combines each stage and provides a daily relative risk for ascospores. Specific experiments are on‐going to further validate the model and develop a decision‐making support system to help farmers decide whether or not to spray against FHB at wheat flowering stage.