INCIDENCE OF DIFFERENT MORPHS OF THE GREENBUG, Schizaphis graminum (ROND.), DISPERSAL ABILITY, NATALITY RATE AND PERCENTAGE OF APHID STAGES ON WHEAT PLANTS IN SOHAG GOVERNORATE, UPPER EGYPT

: Occurrence of all morphs of the greenbug, Schizaphis graminum, dispersal ability, natality rate and percentage of aphid stages were studied on wheat plants at Shandaweel Agricultural Research Station, Sohag Governorate, upper Egypt in 2004/2005 and 2005/2006 seasons. The multiple-regression analysis between biological parameters of aphids versus biotic and abiotic factors was calculated. Generally, data revealed that: 1- The peak numbers of nymphs were (60189 and 37700 nymphs/100 tillers) during 2005 and 2006 seasons, respectively. Nymph numbers were 1.78 times in the first season more than in the second one. 2- Adult females reached the highest level (2724 and 1684 females/100 tillers) during 2005 and 2006 seasons, respectively. The population of adult females was higher in 2005 season (10019 females/100 tillers) than in the second one (5047 females/100 tillers). 3- The percentage of winged adult females in relation to the total numbers of adult females was 100% at the beginning of infestation in the second half of January. Afterwards, winged adults migrated to plants until reached 62.36% and 47.96% in 2005 and 2006 seasons, respectively. The average percentage of winged females was higher in the second season than in the first one.  4- The average of natality rate per female was 16 and 25 nymphs i.e., 2 and 4 nymphs/female per day during 2005 and 2006 seasons, respectively. 5- The average percentage of winged adults (alatae), wingless adults (apterae) and nymphs was (1.5%, 2.8% and 95.7%) and (1.7%, 2.1% and 96.2%) during 2005 and 2006 seasons, respectively. This means that nymphs constituted the highest percentage of individuals in relation to the total of aphid population.  6- The multiple regression analysis to the effect of plant age, maximum, minimum, average daily temperatures and average relative humidity on the total numbers of adult females, data revealed that minimum temperature and average relative humidity in 2005 and 2006 seasons, respectively, played the important role in regulating adult females of S. graminum. While, on the total number of nymphs, data revealed that minimum temperature and average relative humidity were responsible for all reduction of nymph population of S. graminum in 2005 and 2006 seasons, respectively. Data on the natality rate, revealed that minimum temperature and plant age were the most important factors affected natality rate of S. graminum during 2005 and 2006 seasons, respectively