The red palm weevil Rhynchophorus ferrugineus is the most important insect pest for the date palm trees in the middle east and Gulf states.The objective of this study was to investigate the pathogenicity of different concentrations of a natural plant extract (neem) and a synthetic insect growth regulators (IGRs) (flufenoxuron) on the histology of the ovary and testis,and on some biological parameters of the red palm weevil.Prepupae were grouped and treated with three different doses of neem extract (Neem J, 50, 100, 500 ppm) and a synthetic insect growth regulator (flufenoxuron, 0.05, 0.1, 0.5 ppm). The present study demonstrates that both natural (Neem) and synthetic (flufenoxuron) IGRs are capable of disrupting growth, development and reproduction in Rhynchophorus ferrugineus. Growth and developmental disruptions are resulted from the production of high mortality rate, reduction in body length, sex ratio, and morphological malformations, in a dose-dependent fashion. The study further reveals that IGRs exert effects on histological structure of gonads, in this way, disrupt gamete productions. IGRs disrupt female gamete production through their actions on the accumulation of yolk granules (vitellogenesis) and follicular epithelial cells. Disruption of male gamete production was detected by disorganization of testicular cysts and depopulation of these cysts in addition to degeneration and necrosis in germ cell lineage.