Abstract: Pemphigus fuscicornis (Koch) is a pest of sugar beet root in warm and dry regions of Iran. This belongs to the Middle East and south east of Asia fauna. Nymphs establish colonies in root sutures and feed heavily which cause wilting and yellowing in beet near harvest. This study was conducted to determine infestation indices, damage occurrence and the necessity for control measures of this pest. Nymph colonies were monitored in different experimental fields that were planted with commonly used monogerm variety Afshari and then five infested places were selected. Damaged root specimens were sampled from five foci and ranked for infestation, yield and sugar concentration. Results indicated that there were no significant differences in weight, sugar concentration and impurities between indices 1, 2, 3 and none infested beets. Only the sugar concentration of indices 4 showed significant differences with zero infested beets. In the other hand, no specimens were found with the highest population density index (indices 5). Therefore, the sugar beet root aphid populations did not reach to the level of economic damage in these experimental fields. Thus, the control measures such as chemical application and use of resistant varieties may be used when the colonies density increases to the indices four and five throughout the foci in such fields.