Integrating the impact of wheat fungal diseases in the Belgian crop yield forecasting system (B-CYFS)

Field experiments were conducted over four growing seasons to assess the relationship between fungal
disease attacks and wheat grain yield in the agrometeorological part of the Belgian crop yield forecasting
system (i.e., Belgian crop growth monitoring system, B-CGMS) by recalibrating the lifespan of wheat
leaves (SPAN parameter). The results from 133 experimental fields in Belgium (the Wallonia region)
and the Grand-Duchy of Luxembourg were analyzed in terms of site factors such as cultivar, previous
crop, sowing date and geographical area. A significant relationship was found between green leaf area
(GLA) duration expressing the infection pressure (parameter m; using a modified Gompertz model and
calculated from observed GLA) and final grain yield (R2 = 0.79; P < 0.001). Based on this relationship and
by recalibrating the B-CGMS in terms of its SPAN parameter, there was a significant improvement in
estimating final grain yield. From a R2 of 0.11 when the B-CGMS was run with the default SPAN value,
the relationship between observed and simulated yields was strengthened, with a R2 of 0.47 and 0.57,
respectively, when a linear or quadratic relationship was considered between m and SPAN.
Although, from a practical point of view, the m value has to be estimated annually for each spatial
grid or group of grids on the basis of field or possibly remotely sensed data, and although estimating
this parameter is possible only late in the season, these encouraging results illustrate the potential of
integrating pest and disease impact in the B-CGMS.