The estimation of yield losses in wheat from severity of infection by Septoria species

Equations to assist the estimation of national losses from the results of disease surveys carried out at GS75 were derived from five fungicide trials and two inoculation experiments in the field. The equations indicate that the percentage loss in grain yield is equal to 5.412x i 0.6 , 1.011x i or 0.551x ii where x i and x ii are the percentage area infected on the flag and second leaves respectively.