Field experiments were conducted at Kafr El-Sheikh governorate during two successive seasons 2008/2009 and 2009/2010 to study the population fluctuations of some insect pests infesting broad bean plantations namely Liriomyza trifolii (Burgess) ; Aphis craccivora (koch) and Empoasca discipiens Poali. In addition, the effect of certain weather factors (daily mean temperatures and daily mean R.H.) and plant age were studied on the population fluctuations of the previously mentioned pests. The weather factors and plant age had significant effect on the population fluctuations of L. trifolii A. craccivora and E. discipiens,. Also, the relative humidity had shown no significant effect on population fluctuations of the three insect pests during the two seasons 2008/2009 and 2009/2010. The percentage of Explained variance was 83.5& 81.9 % during the two seasons, respectively. The phytochemical contents of the broad bean plant stages, in leaves of Foliage phase, of A. craccivora ; L. trifolii, and E. discipiens were significant during two successive seasons.