Performance and population growth rate of the cotton aphid Aphis gossypii Glover and the associated yield losses were studied in relation to varying nitrogen fertilization levels (90, 110, 150 and 190 ppm) on cucumber, Cucumis sativus L., under greenhouse conditions. The results showed that some parameters in the plant including leaf biomass, water and nitrogen content increased at higher nitrogen fertilization. Aphids developing on cucumber plants receiving the highest nitrogen fertilization had a significantly shorter development time and produced a higher number of nymphs per female than aphids subjected to the other treatments. However, no significant differences were observed in juvenile survivorship at different nitrogen treatments. Aphid adult body weight and mean relative growth rate (MRGR), as well as intrinsic rate of natural increase (rm) were positively correlated with the nitrogen fertilization levels in the treated plants. In addition, aphid abundance and population growth rate (r) were significantly influenced by interactive effect of nitrogen fertilization levels and sampling dates. Plant yield was significantly affected by interactions s between nitrogen fertilization rate and aphid presence. In the absence of aphid the plant yield increased linearly with higher nitrogen fertilization; however, in the presence of aphids the yield decreased linearly with nitrogen fertilization with the lowest yield being produced by plants fertilized with 190 ppm nitrogen. Results are discussed in the context of plan quality effects on aphid population dynamic and the associated yield losses and pest population management.

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