Abstract
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.
Highlights
The red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), is an economically important, tissue-boring pest of date palm in many parts of the world
The experimental insect Prepupal stage of the Red palm weevil, Rhynchophorus ferrugineus were collected from diseased date palm tree at Al-Manaief Al-Gharbia region, Ismaileya governorate
The lethal effect of neem extract on RPW was not obvious in a distinct developmental stage while, the lethal effect of flufenoxuron on RPW was more obvious in the pupal stage
Summary
The red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), is an economically important, tissue-boring pest of date palm in many parts of the world. The female weevils lay their eggs on palms mostly in cracks, crevices and wounds. Another important site of pest entry into the palm is at the leaf axil and from where offshoots emerge. Because of the concealed nature of the larvae, effective methods for the management of the red and other palm weevils have been difficult to develop (Murphy and Briscoe, 1999). The pest has caused large economic losses in date palms worldwide for the last 30 yr (Faleiro, 2006; Murphy and Briscoe, 1999), and still there are no effective control measures. The chemical control of this pest is undesirable, since chemicals lead to the pollution of water
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