Impact of some weather factours, plant age, plant growth stages and sowing date on population fluctuation of some sap-sucking pests attacking fenugreek plants

Field experiments were carried out at Plant Protection Research Station at Qaha, QalubiyaGovernorate for two successive seasons (2010/2011-2011/2012) in order to study the effect of some weather factors ,plant age and growth stages of the fenugreek Plant (Trigonella foenum-graecum L.) during three sowing dates (Oct.31^st, Nov.15^th and Nov.30^th)  on population fluctuation  of three aphid species [pea aphid,  Acyrthosiphon pisum (Harris); cotton aphid , Aphis gossypii (Glover) and Leguminous aphid , Aphis craccivora Koch and cotton thrips, Thrips tabaci Lind. In the first season, population of Aphis spp. had four, two and three peaks in the first, second and third sowing dates, respectively. The four peaks of  aphid population during  first sowing date  recorded mean numbers of 2.0, 9.0, 4.0 and 10.67 insects / 20 buds on Nov., 29^th 2010, Jan.,17^th, Feb., 14^th and  Feb., 28^th 2011, at 29,78, 106 and120 days from sowing date ,respectively. In respect to, second sowing date the first peak of 2.33 moving stages / 20 buds, occurred on Jan., 24^th 2011 at 70 days from sowing date, the second one with mean numbers of 6.0 individuals / 20 buds were recorded on the  Feb., 28^th 2011 at 105 days (plant age). While three peaks through third sowing date represented by mean numbers of 1.0, 3.33 and 2.0 insects per 20 buds on Jan., 10^th, Feb., 21^st and  March, 14^th at 41, 83 and 104  days from sowing date , respectively. In the second season, the peak numbers and account of aphids/20buds were recorded slightly differences. Pea aphid was insignificantly positive correlated with plant age for all sowing dates during two study seasons except for first date in the first season was significantly positive correlated. Also, pea aphid was the more dominant aphid species through three sowing dates during two seasons.  Population fluctuation of T.tabaci had two, five and four peaks at the three sowing dates, respectively, in the first season. But in the second season T.tabaci recorded three, five and four peaks at first, second and third sowing dates, respectively. The three tested sowing dates arranged descending, where the T. tabacipopulation recorded as 7.29, 4.49 and 3.27 insects / 20 buds, respectively, in the first season.  The general trend of T. tabaci infestation in the second season recorded gradually increasing, characterized with significant differences between vegetative, flowering and fruiting stages in the three sowing dates. Also the fruiting stage in the three sowing date is the most stage infested by T. tabaci.
    Statistical analysis of results for the two seasons was indicated that, the suitable date for fenugreek cultivation in Qualibia ,Governorate , Egypt Nov.,15^th  where recorded mean numbers 1.67 ; 2.13  aphids / 20 buds and  4.49 ; 3.31  thrips / 20 buds in the first  and second seasons , respectively, compared with other sowing dates. Also, the fruiting stages in the three sowing dates during two seasons is the most stage infested by T. tabaci followed by flowering and vegetative growth stages expect of, third date in the first season