Evaluation of the Phoma lingam infection with the G2 score. The evaluation occur in the stage G4 of the crop on the collar and on the elongation. Dig out the plant, Realize a cross section at the collar with a pruning, Classify the collars with the rating scale : 1= healthy plant ; 2=0-25% of necrotized surface, 3=25-50% of necrotized surface, 4=50-75% of necrotized surface, 5=75-100% of necrotized surface, 6=plant broke during the evaluation.