الفهرس 
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Abstract
The aphid, leafhopper, planthopper insect species attacking wheat and maize crops were collected in Zagazig district, Sharkia governorate during 2020/2021 & 2021/2022 season. The obtained results can be summarized as follow:
1- survey studies could be summarized as: a)Aphids: Rhopalosiphum maidis (F.) R. padi (L.) Aphis gossypii were collected. b) Leafhoppers: Empoasca decipiens (Paoli), E. decedens (Paoli), Cicadulina china (Ghauri), Balclutha hortensis (Lindb.), Cicadulina bipunctella zeae. were collected c)planthoppers: Sogatella vibix (Haupt) and S. furcifera (Horv) were collected.
2- The highest population density of the aforementioned insects infecting wheat and maize crops occurred in the third sowing date (End of November for wheat) and (End of May for maize), the lowest mean number of insect species were recorded in the first sowing date (Beginning of November for wheat) and (Beginning of May for maize).
3- Giza 171 wheat variety and Single white 2030 maize variety proved to be the least susceptible for aphid, leafhopper and planthopper species.
4- Negative and positive correlation coefficients occurred between potassium and nitrogen fertilization rate and the population density of the aforementioned insects, respectively.
5- Chemical constituents of wheat and maize varieties have a great impact on insect population.
6- Leafhopper Cicadulina china is an insect vector of maize yellow strip virus in maize crop.