Les arthropodes liés aux galbules et aux graines du genévrier thurifère, Juniperus thurifera L., dans les Atlas marocains

Abstract

The arthropods inhabiting cones (berries) and seeds of incense-juniper, Juniperus thurifera L., were surveyed in six sites of the High Atlas mountains and in seven sites of the Middle Atlas mountains. A total of 17 species, including six major phytophagous pests, were identified. The attack periods of the pest species were synchronised with the different phases of cone development. The annual fluctuations in cone crop resulted in a large variation in the percentage of cone damage. However, more than 50 % of the berries were usually damaged. Cone damage increased from the base to the top of the tree crown but the position of the cone within the crown did not influence pest attack. Overall and specific pest damage differed between sites in the High and Middle Atlas mountains. At Tizrag (High Atlas), an average number of 1.1 seeds per cone was observed before insect attack, but the number of full, sound seeds was only evaluated to 0.13 per cone after insect attack. In this stand, we estimated that a tree disseminated 3382 full seeds on the average whilst 24454 were likely to be released before pest attack ; i.e. a decrease of 86.2 %.