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The date palm is the main agricultural base in the southern region of the Saharan Atlas, Algeria and especially at Biskra , Algeria .This crop is threatened by insect pests, such as the white date palm scale Parlatoria blanchardi (Targioni-Tozzetti, 1868) (Hemiptera?Diaspididae). This devastating pest causes premature dryness of the date palm trees, and leads to total loss of the palm. During this study, the white date palm scale completes four cycles or four generations per year. The first generation occurs in early summer during the two study seasons, 2017 and 2018. The second generation is mentioned in mid-July in 2017 and mid-August in 2018. The third generation appears at the end of September in 2018 and mid-October,2018. The fourth generation is mentioned at the end of December in 2017 and mid-January in 2018. Keywords Date palm, Biskra, oasis, date scale, population , dynamic, temperature, humidity

Our study was carried out on the private farm of Mr Chebaani in Sidi Okba in the wilaya of Biskra (Algeria), to test the toxicity of a bio-pesticide of the aqueous extract of Ruta graveolens (Rutaceae), on the larvae and adults of the white scale (Parlatoria blanchardi Targ., 1868, Homoptera, Diaspididae) of the date palm. We sprayed three different concentrations (10, 30 and 50 g / l) of the aqueous extract of the bio-pesticide on the feet of date palm, and to determine the different chemical constituents of the bio-pesticide we carried out a Liquid Chromatography Mass Spectrometry (LC-MS). The study of the effect of the aqueous extract showed that the concentration 50 g/l, gave good results on the larvae and the adults of the white scale, with mortality rates of 85.33% and 64.33 %, respectively. The results also showed that the lethal concentration (LC50%) after 24 hours in the larvae is 3.91 g/l and in adults is 214.2 g/l. LC-MS analysis allowed the identification of 30 components, the main ones are: anethole (15.77 ppm), gardenin B (5.58 ppm), p-coumaroyl glycolic acid (5.17 ppm), 2,3-dihydroxy-1- guaiacylpropanone (5.12 ppm), hesperidin (4.8 ppm), and 3-sinapoyl quinic acid (4.49 ppm).

Climatic variations during the Quaternary period had a considerable impact on landscapes and habitat fragmentation (rivers) in North Africa. These historical events can have significant consequences on the genetic structure of the populations. Indeed, geographically separated and genetically isolated populations tend to differentiate themselves through time, eventually becoming distinct lineages, allowing new species to emerge in later generations. The aim of the present study is to use genetic and morphological techniques to evaluate the major role of the Saalian glaciation (Middle Quaternary) in the establishment of the geographic space and in the evolution of the intraspecific genetic diversity, by tracing the demographic history of barbels belonging to the Luciobarbus pallaryi (Cyprinidae) species in the Guir Basin (Algeria). In this context, two populations, from two distinct and isolated sites, were studied. Analysis of the cytochrome b (cyt b) mitochondrial markers and of the “D-loop” control region has shown that the “upstream” and “downstream” Guir populations are genetically differentiated. The molecular analyses suggest that the upstream population was disconnected from this hydrographic system during the Saalian glaciation period of the Quaternary. Subsequently, it was isolated in the foggaras underground waters in the Great Western Erg, at approximately 320 000 years BP, creating, through a bottleneck effect, a new allopatric lineage referred to as “Adrar”. Conversely, the high genetic diversity in the upstream Guir (Bechar) population suggests that the stock is globally in expansion. These barbels (n=52) were also examined with meristic, morphometric, osteological, and biological features. These data also reveal a complete discrimination between the two populations, with a remarkable and distinctive behavioural adaptation for the Adrar specimens: neoteny.