The rate of infestation of Faba bean of leaf miners Leiomym trifold (Berg.) represented by mean number of larvae and mines / 100 leaves of common bean plants were recorded weekly throughout 2002 and 2003 seasons in experimental farm at Etay El-Baroud Agricultural Research Station El - Behera Governorate . Data indicated that the mean number of 1. tnfoli I (Burg.) Larvae on common bean plant increased as the season progressed and reached its maximum on October 3 b( 237.75 larvae - 307.5 minas / 25 leaves ) during 2002 while during 2003 season the mean number of larvae population achieved the maximum on October 5th (235.00 larvae - 453.25 mines / 25 leaves ) . Throughout the year , the abundance of L . Difohl was relatively law in the beginning of growing seasons but the infestation become more serious in the end of seasons. and produced three generations on common bean pants per season of 2002 and 2003. The 1s` generation was low and occurred from August 29Th to September 12th and from August 29th, to September 14th in 2002 and 2003 respectively, with generation period of (3 weeks). The second generation begins from September 19th to October 10th and from September 21° to October 12Th on 2002 and 2003 season , respectively ( 4 weeks) :The third generation begins from October 17th To November 14th and from October 19th to the November 16th in 2002 and 2003 seasons , respeclively , with generation period of ( 5 weeks ).