An assessment of population fluctuations of citrus pest woolly whitefly Aleurothrixus floccosus (Maskell, 1896) (Homoptera, Aleyrodidae) and its parasitoid Cales noacki Howard, 1907 (Hymenoptera, Aphelinidae): A case study from Northwestern Algeria

The aim of this study was to assess the effectiveness of the parasitoid Cales noacki Howard, 1907 (Hymenoptera, Aphelinidae) in the biological control of the citrus pest woolly whitefly, Aleurothrixus floccosus (Maskell,1896) in Northwestern Algeria. In particular the pest and parasitoid population fluctuations under different environmental conditions were investigated. The study was conducted by examination and sampling of whitefly adult populations on young shoots and catches as well as its parasitoid during a 12-month period by counting the parasite and infested-live larvae. Results showed remarkable variations in abundance indices and infestation rates of larvae and adults that depended on the growth flush in foliage and meteorological conditions of the region. The woolly whitefly manifested three flight periods coinciding with three growth flushes of orange sap; in autumn towards the end of September followed by mid-November with the highest average abundance of 10 individuals per branch and a third flight period in mid-May. Phases of growth flush seemed to have an effect on the temporal distribution of adults over the sampling period from July to June. Pest emergence appeared favorable at 12-20 °C as the minimum interval temperature whereas the maximum varied between 25-33 °C with humidity levels of 50 % and 75 %. As for the incidence of natural enemies on whiteflies, despite their abundance, their impact was not optimum due to the large fluctuations in number of whiteflies. Although the pest-parasitoid complex appears to be important in the orchard, the biological regulation exerted by C. noacki while effective is insufficient for the complete neutralization of citrus woolly whitefly A. floccosus. An integrated approach is needed using additional natural enemies associated with the woolly whitefly

Essential Oils of Three Aromatic Plant Species as Natural Herbicides for Environmentally Friendly Agriculture

[EN] Natural herbicides based on essential oils (EOs) extracted from aromatic plants are gaining relevance in contemporary agriculture. Due to their allelopathic properties, they have an inhibitory effect on the germination and growth of different species, having, in general, the advantage of high specificity. For this reason, the analysis of the effects of these natural compounds on noxious weeds is continuously increasing. In the present study, three commercial EOs extracted from Mentha piperita L., Thymbra capitata (L.) Cav. and Santolina chamaecyparissus L. were tested on two invasive weeds with an increasing presence in southern Europe, Erigeron bonariensis L. and Araujia sericifera Brot. Five concentrations (0.125, 0.25, 0.50, 1 and 2 mu L mL(-1)) were tested in a randomized manner for each essential oil and five replicates with 20 seeds each for E. bonariensis and 10 replicates with 10 seeds each for A. sericifera. Two higher concentrations of 4 and 8 mu L mL(-1) of the three EOs were applied with irrigation on the plants of the two species at the vegetative growth stage. The number of replicas for each treatment and species was 7. The results obtained confirmed the significant inhibitory effects on seed germination and early seedling development, especially in E. bonariensis; of the three EOs, peppermint had the strongest effect, completely preventing germination in both species. Multivariate analysis, performed on several morphological traits scored after one month of treatment in young plants, showed a different pattern: the highest inhibition was recorded in A. sericifera and the greatest reduction in growth in the treatment with the highest dose of Santolina EO. The results obtained revealed the efficacy of these natural compounds and the specificity of their toxicity according to the species and stage of development.Bellache, M.; Torres-Pagan, N.; Verdeguer Sancho, MM.; Benfekih, LA.; Vicente, O.; Sestras, RE.; Sestras, AF.... (2022). Essential Oils of Three Aromatic Plant Species as Natural Herbicides for Environmentally Friendly Agriculture. Sustainability. 14(6):1-22. https://doi.org/10.3390/su1406359612214

Physiological and Biochemical Responses to Water Stress and Salinity of the Invasive Moth Plant, Araujia sericifera Brot., during Seed Germination and Vegetative Growth

[EN] Araujia sericifera is an invasive plant with an increasing presence in South East Spain, where it produces damage to native trees and shrubs and citric orchards. As the climatic conditions in the study area are becoming harsher due to the climate change, the stress tolerance of this species has been studied during germination and vegetative growth. Growth parameters, photosynthetic pigments, ion accumulation, and antioxidant mechanisms were analysed in plants that were subjected to water deficit and salt stress. Seed germination was reduced by salinity but 50% of the seeds still germinated at 50 mM NaCl. The ungerminated seeds did not lose their germination capacity as shown in `recovery¿ germination assays in distilled water. Germination was less affected by osmotic stress that was induced by polyethylene glycol (PEG), and germination velocity increased in the recovery treatments after exposure to NaCl or PEG. Plant growth was practically unaffected by 150 mM NaCl but inhibited by higher NaCl concentrations or severe drought stress. Nevertheless, all the plants survived throughout the experiment, even under high salinity (600 mM NaCl). A. sericifera relative stress tolerance relies, at least to some extent, on effective antioxidant mechanisms that are based on flavonoid biosynthesis and the activation of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, and glutathione reductase.Bellache, M.; Moltó, N.; Allal Benfekih, L.; Torres-Pagán, N.; Mir Moreno, R.; Verdeguer Sancho, MM.; Boscaiu, M.... (2022). Physiological and Biochemical Responses to Water Stress and Salinity of the Invasive Moth Plant, Araujia sericifera Brot., during Seed Germination and Vegetative Growth. Agronomy. 11(2):1-20. https://doi.org/10.3390/agronomy1202036112011

Biodiversité acridienne des zones humides et des écosystèmes forestiers (de [i]Quercus suber[/i] et de [i]Q. canariensis[/i]) : effets du climat et de la végétation

The abundance, richness and seasonal composition of grasshopper communities (Caelifera) were studied in three natural wetland areas, in northeastern Algeria, near El-Tarf and El-Kala. A census of 19 species showed that 12 species were recorded at the station of Chtaïba (Quercus suber forest around 350 m A.S.L.), 11 in the marsh of Mekhada (around 30 m), and 10 in the station of El-Ghorra (Quercus canariensis forest, around 875 m). The different species were grouped into three assemblages, according to class frequency, and their temporal succession depended on the minima of monthly temperature, except at the El-Ghorra station. The assemblages corresponding to each station showed similar species richness and diversity, although their composition was quite different.[br/]The marsh station of Mekhada is characterized by littoral species, such as Eyprepocnemis plorans, Euchorthippus albolineatus, Tropidopola cylindrica and Platypygius platypygius. Together with Chorthippus vagans africanus, P. platypygius seem to be the most remarkable species of the region. There is an important lag in the abundance of adults at both forest stations compared to the littoral station. The richness of grasshopper assemblages was found to depend on the diversity of Poaceae

Recherches quantitatives sur le criquet migrateur Locusta migratoria (Orth. Oedipodinae) dans le Sahara algérien (perspectives de lutte biologique à l'aide de microorganismes pathogènes et de peptides synthétiques)

Locusta migratoria ssp. cinerascens a manifesté récemment des pullulations dans des périmètres irrigués du Sahara central algérien. Le cycle comprend trois générations. La 1ère se développe sur les céréales d hiver et se caractérise par une forte variation temporelle de son sexe-ratio et par un stress de développement (asymétrie fluctuante des élytres). Les 2nde et 3ème se rencontrent sur sorgho et dans des maraîchages et ont un sexe-ratio plus équilibré et peu d asymétrie fluctuante. L étude des régimes alimentaires révèle l originalité des L5 par rapport aux L4 et aux adultes. Les expériences de croissance sur le blé, le sorgho et des graminées adventices rendent compte des anomalies de croissance des populations développées sur le blé. Pour lutter contre ce ravageur, nous préconisons sur le terrain un désherbage des champs. En laboratoire, nous avons comparé l efficacité de trois souches de B. subtilis sur le TL50 des L5, la croissance et la résorption des ovocytes des adultes. La Cry-toxine Cry1 de B. thuringiensis a un effet limitant sur la croissance des larves. Enfin, le neuropeptide-F extrait du Doryphore perturbe le fonctionnement ovarien.Locusta migratoria ssp. cinerascens have spread recently in irrigated perimeters in the Central Algerian Sahara. The cycle comprises three generations. The first one is developed on winter cereals and is characterised by a drastic temporal variation of its sex ratio and a development stress evidenced by the fluctuating asymmetry of tegmina. The second and third ones grow on Sorghum vulgare fields and vegetable gardens and show a balanced sex ratio and a low level of fluctuating asymmetry. The diet study revealed the originality of the L5 (fifth instar larvae) from the L4 and adults. The experiments of growth with different species of Poaceae given as food supply shed a light on the growth abnormality of populations developed on T. durum. To control this insect pest, we recommend at the field level a careful weeding. At the laboratory level, we have tested the efficiency of three strains of B. subtilis on the LT50 in L5, and on the development and resorption of oocytes in adults. B. thuringiensis Cry1-toxin shows a limiting effect on larvae growth. Finally, the neuropeptide-F extracted from Potato beetle disturbs ovarian physiology.LIMOGES-BU Sciences (870852109) / SudocSudocFranceAlgeriaFRD

Why the aphid Aphis spiraecola is more abundant on clementine tree than Aphis gossypii?

International audienceAphis spiraecola and Aphis gossypii cause harmful damages on clementine tree orchards. Weekly surveys measured the abundance of aphids (larvae, winged and wingless adults) as well as of auxiliary insects and parameters of energy metabolism. Correlatively, soluble carbohydrates, total free amino acids, free proline and condensed tannins were quantified in control and infested leaves. Both aphid species showed parallel temporal variations, but A. spiraecola was consistently more abundant regardless of the stage. Amino acids had a positive effect on both aphid species abundance, but neither condensed tannins nor auxiliary insects seemed to modulate aphid populations. Interestingly, the leaf carbohydrate content was positively correlated with the abundance of A. spiraecola, but not with that of A. gossypii. Moreover, A. gossypii's abundance was significantly down-regulated by high proline concentrations. Thus, the higher abundance of A. spiraecola could be explained by a better tolerance to high proline contents and a better conversion of foliar energy metabolites

Effects of Four-Week Exposure to Salt Treatments on Germination and Growth of Two Amaranthus Species

Soil salinity represents one of the most restrictive environmental factors for agriculture worldwide. In the present study, the salt tolerance of two weeds of the genus Amaranthus, A. albus and A. hybridus, the latter cultivated as green vegetable in Africa, were analysed. Both species showed a remarkable salt tolerance phenotype during germination and vegetative growth. To evaluate the percentage and rate of germination, seeds were germinated in Petri dishes in a germination chamber under increasing concentrations up to 300 mM NaCl. Higher concentrations of salt ranging from 150 to 600 mM NaCl were applied for one month to plants grown in individual pots in the greenhouse. All seeds of A. albus germinated in the control and almost half of the seeds under 200 mM NaCl, but only 4% of the seeds under 250 mM NaCl. In A. hybridus, germination was considerably lower in all treatments and was completely prevented at 250 mM NaCl. The plant growth of both species was severely affected by high salt concentrations of 450 and 600 mM NaCl, but not under lower concentrations. At this stage of the biological cycle, A. hybridus showed a higher salt tolerance, as indicated by the smaller reduction in its growth parameters. The dry weight of leaves and roots of plants receiving 600 mM NaCl decreased in comparison to control: less than 60% in A. hybridus but more than 70% in A. albus. The salt tolerance of the two species contributes to their invasive potential, but on the other hand represents a useful trait when considering them as potential crops for the future

Effects of four-week exposure to salt treatments on germination and growth of two Amaranthus species.

[EN] Soil salinity represents one of the most restrictive environmental factors for agriculture worldwide. In the present study, the salt tolerance of two weeds of the genus Amaranthus, A. albus and A. hybridus, the latter cultivated as green vegetable in Africa, were analysed. Both species showed a remarkable salt tolerance phenotype during germination and vegetative growth. To evaluate the percentage and rate of germination, seeds were germinated in Petri dishes in a germination chamber under increasing concentrations up to 300 mM NaCl. Higher concentrations of salt ranging from 150 to 600 mM NaCl were applied for one month to plants grown in individual pots in the greenhouse. All seeds of A. albus germinated in the control and almost half of the seeds under 200 mM NaCl, but only 4% of the seeds under 250 mM NaCl. In A. hybridus, germination was considerably lower in all treatments and was completely prevented at 250 mM NaCl. The plant growth of both species was severely affected by high salt concentrations of 450 and 600 mM NaCl, but not under lower concentrations. At this stage of the biological cycle, A. hybridus showed a higher salt tolerance, as indicated by the smaller reduction in its growth parameters. The dry weight of leaves and roots of plants receiving 600 mM NaCl decreased in comparison to control: less than 60% in A. hybridus but more than 70% in A. albus. The salt tolerance of the two species contributes to their invasive potential, but on the other hand represents a useful trait when considering them as potential crops for the future.Bellache, M.; Benfekih, LA.; Torres-Pagán, N.; Mir Moreno, R.; Verdeguer Sancho, MM.; Vicente, O.; Boscaiu, M. (2022). Effects of four-week exposure to salt treatments on germination and growth of two Amaranthus species. Soil Systems. 6(3):1-16. https://doi.org/10.3390/soilsystems60300571166