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The present investigation aimed to study the influance of some soybean varieties (Karfordid, Giza 22 and Giza 21) under the effect of different potassium fertilization levels (zero, 25, 50 and 75) kg potassium sulphate /feddan). Effects of some chemical contents (protein, carbohydrate and pH values) on the infestation of aphids, leafhoppers, trips and whitefly insects were also investigated. The obtained results showed pronounced differences in the population density of these insects under test as influenced by the aforementioned agricultural practices. The tested soybean varieties can be arranged descending according to the degree of infestation with insects as following Giza 21, Giza 22 and Karfordid. Chemical analysis results showed a positive relationship between protein and carbohydrate contents and aphids, leafhoppers, whitefly and thrips infestation in soybean varieties, while reverse relationship between pH values and insect infestation. Negative relationship between insect infestation and quantity of yield was also recorded. Therefore, it could be recommended that potassium fertilization 75 kg potassium sulphate /feddan along with the most suitable plant variety must be included in the integrated pest management programs of soybean plants.

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Ability of Aphis craccivora Koch to transmission of faba bean necrotic yellow virus (FBNYV) on broad bean plants was studied under laboratory conation. These studies were carried out in the laboratory of plant protection institute, Zagazig. The result show that the acquisition threshold feeding periods were ranged between 60 -120 min. Incubation periods in A. craccivora ranged between 120-160 min., while in celery plants was 12 -18 days.