Seasonal fluctuations and the relative susceptibility of eleven breeding lines of faba bean in addition to the local variety Sakha 3 to the infestation by the serpentine leaf miner. Liriomyza trifolii (Burgess ) were investigated at Farm of Sakha Agricultural Research Station during two successive growing seasons; 2005/06 and 2006/07.  Data collected weekly using binocular microscope and by visual counts  indicated that the population of the leaf miner, L. trifolii was higher in the second season than in the first one and the highest number of the live larvae was recorded during the second half of February on all tested breeding lines and variety Sakha 3 .    The mean number of L. trifolii larvae indicated that the highest number was recorded on the line  1566/574  in the first season, while in the second season the highest number was observed on line 461.Sakha1. On the hand, the breeding line 1618/837 recorded the lowest number of larvae during the two study seasons. Regarding to the susceptibility degree to this insect, line 461.Sakha1 appeared as highly susceptible, while the lines 1566/574; 1571/638; 81/38; 96/67 and variety Sakha 3 appeared as susceptible.   The other lines showed some sort of resistance, where 1561/492; 1610/705; 1618/ 846 and 92/59 appeared as low resistant lines, but 1618/837 appeared as moderately resistant one .   Thus, from the gained results, entomologists and the plant breeders could develop a management strategy for the control of the  leaf miners on faba bean in north Delta through selecting lines that have a desirable resistance levels.