An experiment was carried out to study the effect of planting date, climatic factors and plant age on the population density of Leafminers, Liriomyza spp. infesting fenugreek plants in Plant Protection Research Station at Kaha region during two successive seasons 2010-2011 and 2011-2012. The obtained results revealed that the population density of Liriomyza spp larvae on fenugreek plants differed significantly according to the planting dates (Oct.,31st, Nov., 15thand Nov.,30th) during the two studied seasons. Planting of fenugreek seeds in the early planting date (Oct., 31st) lead to plants suffered from the highest infestation by Liriomyza spp. larvae. On the contrary, sowing the fenugreek at the second date (Nov., 15th) can be reduced the infestation rate of this insect pest. The population density of leafminers, Liriomyza spp increases by increasing the plant age. The lightest population was recorded during the vegetative stage. While the fenugreek plants infested by the heaviest population during flowering and fruiting stages. Statistical analysis of correlation coefficient values showed that the effect of climatic factors on the population density of Liriomyza spp. was differed positive or negative correlation according to plant stages (vegetative, flowering  and fruiting stages) during two studied seasons. The population density of Liriomyza spp. correlated positively with plant age except for the early planting date (Oct., 31st) in the second season, as the calculated (r) values were 0.15, 0.68 and 0.48 for the three planting dates in the first season and -0.05,0.43 and 0.62 in the second  season, respectively. The climatic factors were more effective on leafminers population when comparing with plant age, as the explained variance (E.V. %) were 55.73, 70.83 and 42.93% for the three planting dates in the first season and 69.72, 78.59 and 39.40% in the second season, respectively. The combined effect of the tested weather factors (maximum & minimum temperature maximum & minimum RH% and average wind speed) and plant age together on Liriomyza spp. population in the tested planting dates on different stages of fenugreek plants were 59.90, 73.15 and 66.82% at the three planting dates during first season and 72.74, 79.51 and55.82% during second season, respectively.