Over-wintered adult carrot psyllids damage carrot seedlings by feeding on the leaves. Severe carrot psyllid damage can totally prevent root formation. The carrot psyllid flight is monitored by yellow sticky traps in Finland. However, farmers have criticized the reliability of the monitoring system. The aim of this study was to define the limit of carrot psyllids feeding intensity which a carrot seedling can tolerate without considerable yield losses. We studied different carrot psyllid feeding intensities on different growth stages of carrot seedlings in a greenhouse experiment. The bigger carrot seedlings had constantly lower leaf damage percent and higher root weight than the smaller seedlings, which suggests that bigger seedlings are more tolerant. The need for dynamic carrot psyllid threshold for different growth stages of carrot is discussed.