الفهرس 
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Abstract
The present investigations were undertaken at the Experimental Farm of Assiut University, Agronomy Department, throughout 2013-2014 and 2014-2015 wheat growing seasons in addition to some laboratory experiments.
The objectives of this work were:
1- Studying the population of cereal aphids.
2- Studying factors (biotic and abiotic) affecting cereal aphid populations.
3- Studying the mechanisms underlying aphid-parasitoid dynamics in the field.
4- Studying the effect of some agricultural practices such as wheat cultivars and nitrogen fertilization on the aphid populations.
5- Determine yield losses due to aphid infestations.
6- Studying some biological aspects of Rhopalosiphum padi L. and Schizaphis graminum (Rondani) as well as their common primary parasitoid Diaeretiella rapae (M’Intosh) under different constant temperatures.
7- Studying biochemical and physiological changes in wheat leaves in relation to nitrogen fertilization and how these changes affect physiological parameters of both R. padi and S. graminum.
8- Studying the impact of parasitization by hymenopterous parasitoid D. rapae on chemical composition and some antioxidant enzymes of its host R. padi under laboratory condition.
9- Scanning electron microscope studies for R. padi and S. graminum and their dominant parasitoid D. rapae.