Impact of some alternative methods to chemical control in controlling aphids (Hemiptera: Sternorrhyncha) and their side effects on natural enemies on young Moroccan citrus groves

Aphid control in Moroccan citrus orchards is based mainly on carbamate and neonicotinoid sprays, especially methomyl and imidacloprid. The extensive use of these insecticides may have side effects on natural enemies and environment quality and raises human health concerns. This research aimed to assess the control of aphids with insecticidal soap, kaolin and augmentative biological control using the indigenous predator Adalia decempunctata L. (Coleoptera: Coccinellidae). The insecticides were applied and the predators were released in April 2009 and 2010. Under field experimentation, the methomyl and imidacloprid foliar pulverization were very effective against aphids. In contrast, the insecticidal soap and kaolin application were less efficient while A. decempunctata adults were effective only in the first week after release. The side effects on beneficial insects were also assessed and discussed. The possibility of employing A. decempunctata in an integrated pest management package in citrus groves is discussed in relation to effectiveness and side effects on beneficial arthropods.     

YIELD AND FRUIT QUALITY OF ALMOND,PEACH AND PLUM UNDER REGULATED DEFICIT IRRIGATION

• Regulated deficit irrigation was assessed in almond, peach and plum over 3 years.• Fruit-growth slowdown stages are appropriate periods to apply deficit irrigation.• Peach yields were unaffected under a regulated deficit irrigation of 75% ET_C.• Regulated deficit irrigation of 50% ET_C maintained yields of almond and plum.• Fruit quality improved under regulated deficit irrigation.The effects of regulated deficit irrigation (RDI) on the performance of almond cv. Tuono, peach cv. JH-Hall and plum cv. Stanley were assessed on the Saiss Plain (NW, Morocco) over three consecutive growing seasons (2011–2013). Irrigation treatments consisted of a control, irrigation applied to fully satisfy crop water requirements (100% ET_C), and two RDI treatments, irrigation applied to 75% ET_C (RDI-75) and 50% ET_C (RDI-50). These three treatments were applied during fruit-growth slowdown periods corresponding to Stages II and III in almond and Stage II in peach and plum. Yield and fruit quality traits were determined. The effect of RDI differed between species. Yield and fruit size were reduced significantly only in peach under RDI-50. Fruit quality improved in this species in the first year of the experiment, with an increase of sugar/acid ratio and polyphenol content. Plum quality also improved but the effects were significant only in the second and third years. Similar results were recorded in almond kernel, but their epidermal grooves were deeper under RDI-50, and this may have affected their commercial value. It is concluded that water can be saved during the fruit-growth slowdown period by up to 25% in peach and 50% in almond and plum with improvements in fruit quality without affecting total yield.     

Breaking seed dormancy in Cupressus atlantica Gaussen, an endemic and threatened coniferous tree in Morocco

Cupressus atlantica Gaussen (Cupressaceae) is an endemic and endangered coniferous tree geographically restricted to the N’Fis valley in South-Western Morocco. Like many forest species, C. atlantica exhibits dormancy which delays and reduces germination. To improveseed germination, different pre-treatments were conducted on C.atlantica seeds after storage for different periods (one, two and five years) including: scarification with sandy paper; soaking seeds in hot distilled water at 60℃and 80℃for 15 min and soaking seeds for 48 h in agibberellic acid (GA3) at 1,000 and 2,000 mg·L-1. Results showed that scarification with sandy paper increased the germination rate of Atlas cypress by up to 67%, indicating that the species possess essentially anexogenous dormancy (physical dormancy) due to the hard seed coat(hardseededness). Exogenous application of gibberellic acid (GA3) at1,000 mg·L-1 was also effective in breaking seed dormancy and germination induction. These two treatments induced faster speed germination expressed by low number of days to first germination (8 10days) and low values of mean germination times (MGT). However,germination rate, under any treatment, is greatly dependent on the year of seed collection. Seeds collected in year 2004 gave the highest value,suggesting that even after five years of storage, the germination capacity of C. atlantica seeds could remain high. This observation is very interesting in the exsitu conservation of such endemic and endangered species where the production of seeds is irregular over the years.     

Chemical Composition and In Vitro Antioxidant and Antimicrobial Activities of the Marine Cyanolichen Lichina pygmaea Volatile Compounds

Volatile compounds from the marine cyanolichen Lichina pygmaea, collected from the Moroccan Atlantic coast, were extracted by hydrodistillation and their putative chemical composition was investigated by gas chromatography coupled to mass spectrometry (GC/MS). Based on the obtained results, Lichina pygmaea volatile compounds (LPVCs) were mainly dominated by sesquiterpenes compounds, where γ-himachalene, β-himachalene, (2E,4E)-2,4 decadienal and α-himachalene were assumed to be the most abundant constituents, with percentage of 37.51%, 11.71%, 8.59% and 7.62%, respectively. LPVCs depicted significant antimicrobial activity against all tested strains (Staphylococcus aureus CCMM B3, Pseudomonas aeruginosa DSM 50090, Escherichia coli ATCC 8739 and Candida albicans CCMM-L4) with minimum inhibitory concentration (MIC) values within the range of 1.69–13.5 mg/mL. Moreover, this LPVC showed interesting scavenging effects on the 2,2-diphenyl-1-picrylhydrazyl radical with an IC₅₀ of 0.21 mg/mL. LPVCs could be an approving resource with moderate antimicrobial potential and interesting antioxidant activity for cosmetics and pharmaceutical applications.     

Nurse shrubs increased the early growth of Cupressus seedlings by enhancing belowground mutualism and soil microbial activity

The influence of shrubs used as nurse plants was tested on the growth of Cupressus atlantica, on microbial activity and on arbuscular mycorrhizal (AM) soil potential in a Mediterranean environment. An experimental plantation was conducted combining uninoculated, arbuscular mycorrhized Cypress seedlings and an association between Lavandula stoechas planted close to newly planted C. atlantica seedlings. After three years plantation, this association between C. atlantica and L. stoechas lead to a higher growth of C. atlantica and better soil microbial characteristics compared to the control treatment. AM mycelium network, total microbial activity, dehydrogenase activity, phosphate-solubilizing fluorescent pseudomonads and N, P nutrient uptake by C. atlantica, were significantly higher in the presence of L. stoechas than those recorded in the other treatments. This pioneer shrubs facilitates the early establishment of Cypress seedlings by improving soil microbial characteristics and AM fungus community development. Given that the facilitative effect of one plant species to another increases with abiotic stress, the benefits of this technique would be useful in reforestation programs undertaken to rehabilitate degraded areas in Mediterranean region.     

Contributions of indigenous arbuscular mycorrhizal fungi to growth of retama monosperma and acacia gummifera under water stress (case study: essaouira sand dunes forest)

ABSTRACT

Two leguminous plant species: Retama monosperma and Acacia gummifera were selected for water deficit tolerance test for future use in reforestation programs of the Atlantic sand dunes forest of Essaouira region. Mycorrhizal fungal colonization was used to help plants amend the water deficit. To assess R. monosperma and A. gummifera response to water stress and the effectiveness of mycorrhizal formation alleviating it, two categories for each plant species were made, one inoculated with mycorrhizal fungi and the other not, were submitted to a hydric deficit treatment of four levels for 6 months. This treatment impact on the plants was assessed by comparing root/shoot dry weight ratios, levels of nitrogen and phosphorus, and by measuring mycorrhizal colonization frequencies and intensities. Results showed that these parameters were significantly affected by water deficit. The presence of the mycorrhizal fungi had significantly enhanced plants phosphorus uptake by 72–124% for Acacia gummifera and 87–161% for Retama monosperma. Nitrogen uptake was increased by 134–388% for Retama monosperma and 510–901% for Acacia gummifera. The colonization frequencies changed significantly only for the treatment extreme level and stayed between 80%-90% for the other levels. The mycorrhization intensities showed significant lessening between each treatment level decreasing from 35% to 10%.     

Comparing growth and fine root distribution in monocultures and mixed plantations of hybrid poplar and spruce

Disease prevention, biodiversity, productivity improvement and ecological considerations are all factors that contribute to increasing interest in mixed plantations. The objective of this study was to evaluate early growth and productivity of two hybrid poplar clones, P. balsamifera x trichocarpa (PBT) and P. maximowiczii x balsamifera (PMB), one improved family of Norway spruce (Picea glauca (PA)) and one improved family of white spruce (Picea abies (PG)) growing under different spacings in monocultures and mixed plots. The plantations were established in 2003 in Abitibi-Témiscamingue, Quebec, Canada, in a split plot design with spacing as the whole plot factor (1 × 1 m, 3 × 3 m and 5 × 5 m) and mixture treatments as subplot factor (pure: PBT, PMB, PA and PG, and 1:1 mixture PBT:PA, PBT:PG, PMB:PA and PMB:PG). Results showed a beneficial effect of the hybrid poplar-spruce mixture on diameter growth for hybrid poplar clones, but not for the 5 × 5 m spacing because of the relatively young age of the plantations. Diameter growth of the spruces decreased in mixed plantings in the 1 × 1 m, while their height growth increased, resulting in similar aboveground biomass per tree across treatments. Because of the large size differences between spruces and poplars, aboveground biomass in the mixed plantings was generally less than that in pure poplar plots. Leaf nitrogen concentration for the two spruce families and hybrid poplar clone PMB was greater in mixed plots than in monocultures, while leaf nitrogen concentration of clone PBT was similar among mixture treatments. Because of its faster growth rate and greater soil resources demands, clone PMB was the only one showing an increase in leaf N with increased spacing between trees. Fine roots density was greater for both hybrid poplars than spruces. The vertical distribution of fine roots was insensitive to mixture treatment.     

Seasonality of mycorrhizal attributes,soil phosphorus and nitrogen of Juniperus phoenicea and Retama monosperma boiss. in an Atlantic sand dunes forest

Seasonal variation of mycorrhization attributes in a degraded ecosystem seems to be key information in conceiving rehabilitation programs that use mycorrhized plantations specific to that ecosystem. In order to record seasonality of arbuscular mycorrhizal fungi in an Atlantic sand dunes forest, root colonization and spores abundance alongside rhizospheric phosphorus and nitrogen of two plant species: Juniperus phoenicea and Retama monosperma, endemic to Essaouira sand dunes forest, were followed through three years. The findings were tested for statistical significance and correlated among each and to some meteorological variables: temperatures, precipitations, and humidity. Results showed that mycorrhization frequencies and intensities and spores densities changed seasonally. They had their peak at late winter-early spring and their low at summer. Phosphorus and nitrogen evolved significantly following seasons. Significant negative correlation was noted between phosphorus and mycorrhizal attributes evolution. Nitrogen correlated positively and significantly though weakly with R. monosperma mycorrhizal attributes. The correlations between mycorrhizal attributes and meteorological variables were not all evident except for temperatures and temperatures-precipitations combination, which had a direct negative impact on mycorrhizal attributes.