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sur le développement des zones arides et semi-arides

Titre : Ecological studies on major insect pests that effect juniperus procera fruits and their natural enemies in Abha province

Auteur : Al-Kahtani, Hamed Ali

Université de soutenance : King Abdulaziz University

Grade : Master 2003

Résumé
A field and laboratory study was conducted on the major important insect pasts infesting the fruits of Arar plant (Juniperus procera Hoschst) during the period \." 2001 -2002. The study was concentrated on intensive field and laboratory , surveys in 4 geographical locations within the premises of Abha province including the protectorate of Rayda, Al-Azziza, Qarada and Al-Nemees. Different technologies were used to determine the very predominant pests, their time-growth curves and the relationship between population density of these insect pests and the natural enemy complex made of (predators, parasitoids and true spiders). In addition to that the percentage infestation of the fruit pests was determined during fruit ripening which reached 61 % in the study area in Rayda protectorate. Two major insect pests on Arar fruits were very prominent the first was Strepsicrates cryptosema (order : Lepidoptera) that belong to the family of fruits and seed worms (Tortricidae). The second pest was Arar fruit bug Taylorilygus sp. (order : Hemiptera) that belongs to family of plant bugs (Miridae). It was evident from this study that eggs and nymphs of the Arar plant bug is affected by two endoparasitoids. The fruit bug eggs parasitoid of the genus Telenomus that belongs to family Scelionidae, however it was observed that from infested nymphs emerged parasitoids of the genus Megastigmus that belong to family Torymidae. Moreover from larvae of fruit worms was observed that the emergence of parasitoids that belong to the family Ichneumonidae, but these parasitoids needed taxonomic identification. Because we were unable to confirm their generic and specific names, therefore considered new records. From laboratory incubation studies the objective was determine field parasitism that endoparasitoids of the eggs of Arar fruit bugs which gave a level of 17.41%, however nymphs parasitoids gave a level of 69.92% whereas the level of parasitism of the larvae of Arar fruit worms 12.67% especially during the peak activity period during October. In addition to that, the natural enemy complex of predators, parasitoids and true spiders was determined but it was evident that the insect endoparasitoids remain the promising biological candidates that could be recommended for more intensive biological studies including fecundity, laboratory mass rearing and release within the premises of Arar forest natural ecosystem in order to determine their high efficiency in reducing and curbing the populations of the major insect pests of Arar plant.

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