Etat actuel de l'infestation par Solanum elaeagnifolium Cav. pour les différentes cultures du périmètre du Tadla (Maroc)

Present state of Solanum elaeagnifolium Cav. infestation in different crops of the Tadla perimeter (Morocco) The present state of infestation by Solanum elaeagnifolium Cav. in crops of the whole agricultural region of the Tadla (Central Morocco) is presented. Using the ecological profile method, it was found that, on the one hand, the Béni Amir perimeter (north Tadla) is much more heavily infested than the Béni Moussa perimeter (south Tadla) and, on the other, infestation is heaviest in spring crops (cotton, maize, sesame). A map attached to the text shows the exact distribution of the species within this region.     

Evaluation du stock en semences de la morelle jaune (Solanum elaeagnifolium Cav.) dans le sol du Tadla (Maroc)

Assessment of the stock of Solaneum elaeagnifolium Cav. seeds in the soil of the Tadla (Morocco) On the basis of soil samples from four fields on the irrigated perimeter of the Tadla (Central Morocco), selected from the area most heavily infested with Solanum elaeagnifolium, estimates of the stock of seeds of this perennial weed revealed a mean value of 375 seeds m^?2 to a depth of 60 cm (dead + viable seeds). The average for the viable seed stock, however, is 163 seeds m^?2 to a depth of 60 cm, or an average of 43·5% of the total stock of seeds counted. The average distribution profile of the seeds of S. elaeagnifolium in the soil is as follows: 71·7, 25·1 and 3·2%, respectively, in the 0–20, 20–40 and 40–60 cm horizons. The vertical distribution of viable seeds followed the same profile as the overall stock; thus we found 73 and 27% of viable seeds were located in the 0–20 and 20–40 cm horizons, respectively.     

Ecological grouping of Solanum elaeagnifolium: a principal weed in the irrigated Tadla plain (central Morocco)

In order to study the ecological relationships between Solanum elaeagnifolium Cav. and the main biotic and abiotic factors in the irrigated arid Tadla plain (central Morocco), the theory of mutual information and corrected frequency profiles has been adopted. The main ecological factors taken into account in this study were the climate, soil, texture, salinity, irrigation, type of land use and the intensity of farming. The growth and extension of S. elaeagnifolium was found to be controlled by the arid and semi-arid Mediterranean climate, by soil type and by technical and agronomic factors.     

Diversité floristique et biologie des adventices de la région du Tadla (Maroc)

Dans le but d'inventorier les adventices des cultures de la région du Tadla (Maroc Central), 345 champs cultivés ont fait l'objet de relevés phytoécologiques. Trois cent trente espèces adventices appartenant à 50 familles botaniques ont ainsi pu être identifiées: 84% sont des dicotylédones (essentiellement Compositae, Leguminosae, Cruciferae, Caryophyllaceae, et Umbelliferae) et 73% sont des annuelles. Une brève étude agronomique a permis de distinguer 70 espèces ayant une nuisibilité non négligeable vis à vis des différentes cultures de la région. Inventory and biology of cropland weeds of the Tadla region (Morocco) An inventory of cropland weeds of the Tadla region (Central Morocco) was made, based on samples from 345 cultivated fields. Three hundred and thirty species were identified, belonging to 50 botanical families: 84% of the species were dicots (mainly Compositae, Leguminosae, Cruciferae, Caryophyllaceae, and Umbelliferae), and 73% were annuals. Seventy species are important cropland pests. Ueber die Floristik und Biologie der Unkräuter in der Region von Tadla (Marokko) Ziel dieser Studie war eine Inventaraufnahme der Ackerunkräuter in der Region Tadla (Zentral-marokko); zu diesem Zweck wurden in 345 Feldkulturen phytoökologische Bestandesaufnahmen durchgeführt. Dabei wurden 330 Unkrautarten aus 50 Familien identifiziert; davon waren 84% Dikotyledonen (hauptsächlich Compositen, Leguminosen, Cruciferen, Caryophyllaceen und Umbelliferen) und 73% Anuelle. 70 Arten verursachten in verschiedenen Kulturen starke Schädigungen.     

Review of the current situation for Solanum elaeagnifolium in the Mediterranean Basin

Silverleaf nightshade (Solanum elaeagnifolium, Cav.) is one of the important invasive plant species in Mediterranean Basin countries. Over the last 60 years, this plant has gone from a few accidental introductions to near monospecific populations in many areas of the Mediterranean Basin (in particular Greece and Morocco). Recent findings from Lebanon show that the invasion is ongoing. Solanum elaeagnifolium has a negative impact on crops, causing up to 75% yield loss, as well as an indirect impact by harbouring plant pests and diseases. Solanum elaeagnifolium is toxic to livestock and has a negative affect on the quality of life for humans. Losses of potential resource or revenue caused by its invasion include: decreased forage quality on grazing lands; decreased cropping land and amenity values of public space; increased water loss; increased water conveyancing costs; and increased forest restoration costs. Available control techniques need to be strengthened to reduce the impact of S. elaeagnifolium and prevent its spread. More attention needs to be devoted to biological control, which could provide regional management of this invasive alien plant. Sustainable management of S. elaeagnifolium will require coordination, education and support across the affected countries. Governments must have the means to detect, manage and control S. elaeagnifolium.     

Etat actuel de l’infestation par la morelle jaune (Solanum elaeagnifolium Cav.) au Maroc*

Signalée pour la première fois au Maroc en 1949, la morelle jaune (Solanum elaeagnifolium Cav.) est devenue à partir des années 80 une adventice préoccupante à l’échelle nationale. Dans un premier temps, l’infestation est restée limitée à la région du Tadla. Mais vingt ans ont suffi à la morelle jaune pour sortir de son berceau et se propager vers des régions éloignées. Des études et des enquêtes effectuées au Maroc ont permis de souligner la grande diversité et l’efficacité de facteurs de dissémination tels que: le fumier organique, les ovins, l’eau d’irrigation, les machines agricoles, les plants en motte et le vent. Toutefois, les trois premiers facteurs restent les plus importants. Suivant les conditions locales, certains de ces facteurs de dissémination deviennent prépondérants et peuvent être simultanés ou successifs.     

Study on the behaviour of imazapyr in two Moroccan soils

Imazapyr owes its importance in Morocco to its success in controlling the perennial weed Solanumelaeagnifolium Cav., which infests the Tadla area. Persistence and mobility of imazapyr has been studied in two Moroccan soils from the Rabat area, with differing organic matter content (red and organic soils), under laboratory conditions at 75% of their field capacities and 25–28 °C. Residue analysis was performed on the basis of a bioassay test using lentil (Lens culinaris Medic.) as indicator species. The residual activity of imazapyr accounted for 69%, 25%, 50% and 62%, 46%, 66% of the initial activity for the red and organic soils at 1, 5 and 10 mg L^?1 respectively. The half-lives varied between 25 and 58 days for the red soil and 55 and 58 days for the organic soil. In the organic soil, imazapyr was highly mobile under the irrigation regime applied. Most of the activity was found in the first 3 × 75 mL of the effluents. A following biotest with the leached soil showed low remaining residual activity.     

Solanum elaeagnifolium,a potential source of Potato virus Y (PVY) propagation*

In the context of an epidemiological study on Potato virus Y (PVY) in potato crops, Solanum elaeagnifolium Cav. was included in the weeds prospected. Surveys were carried out in four seed potato areas: Cap Bon, Manouba, Jendouba and Kairouan. S. elaeagnifolium was found in all areas, except Cap Bon. Virus‐like symptoms were observed on some S. elaeagnifolium plants in the field, i.e. leaf mottling and curling. Aphids were collected on these plants and were identified as Myzus persicae and Aphis fabae, both known to colonize potatoes and to transmit the standard PVY^N isolate with transmission efficiencies of 95% and 43%, respectively. Forty‐seven plant samples were tested with ELISA for the presence of PVY. Positive reactions were obtained from 2/6, 5/18, 8/23 samples collected in Manouba, Jendouba and Kairouan, respectively. Virus transmission was carried out using M. persicae as vector from two samples of each region onto plantlets of Nicotiana tabacum cv Xanthi. All inoculated plantlets displayed typical symptoms of the PVY^N strain group, confirmed by serological testing using specific antibodies. This is the first report of a PVY natural infection on S. elaeagnifolium in Tunisia. The abundance of this weed, its over‐wintering status and the high rate of PVY‐infected plants (31.9%) allow us to deduce that S. elaeagnifolium must be considered a reservoir species of PVY under natural conditions in Tunisia and probably in other Mediterranean countries. The presence of efficient aphid vectors of PVY on this weed in crops is additional evidence that S. elaeagnifolium may become a problem by acting as a source plant for PVY spread in potato crops.     

Influence de la densité et de la période de concurrence de Solanum nigrum L. sur la tomate de semis direct, en relation avec le désherbage

Effects of density and period of competition by Solanum nigrum L. on direct seeded tomatoes in relation to weed control The effects of density and period of competition from Solanum nigrum L. were measured in direct seeded tomatoes given weed control treatments currently used in south-east France. S. nigrum emerging after a diquat treatment at the 2–3 leaf stage of the crop and thinned to low densities (<12.8 plants ha^?1) at the 5–6 leaf stage of the crop caused significant yield loss if left to compete with the crop until harvest. Yield reduction was smaller if the same weed densities were present only until the onset of flowering. The regression curves of yield on weed density differed as annual climatic variations affected sowing date and plant growth; a comparison between years was made using the relation ‘crop yield × weed biomass/crop biomass’. Significant interactions between weed density and period of competition were found with yield of both green and red fruit. For late sown crops with low densities of S. nigrum two weed control treatments at the 5–6 leaf stage and at the onset of flowering were sufficient to prevent yield loss.     

Ophelimus maskelli (Ashmead) et son parasitoïde Closterocerus chamaeleon (Girault) (Hymenoptera: Eulophidae) au Maroc

Leaf galls causing severe damage were observed on Eucalyptus camaldulensis in the Gharb‐Maâmora region in 2002 due to Ophelimus maskelli (Ashmead) (Hymenoptera: Eulophidae) reported for the first time in Morocco. Since then, this pest has spread to other eucalyptus stands nationwide. During field investigations, the authors noted that the degree of infestation of Eucalyptus camaldulensis differs from one region to another and were classified on a three‐level scale: low, moderate or high. The study of the life cycle of the insect in the field and in the laboratory revealed the presence of two generations per year. This work has shown that Closterocerus chamaeleon (Hymenoptera: Eulophidae), a parasitoid used successfully in other EPPO countries as a biological control agent, is present in Morocco. The rate of parasitism was very high, which consequently resulted in the lack of damage caused by the gall pest on Eucalyptus camaldulensis in Morocco.     

New weed species recently introduced into Morocco

Twelve species were identified as having been introduced into Morocco since 1980. These were Abutilon theophrasti Medik., Ammannia coccinea Griseb. Brachiaria eruciformis (Smith) Griseb. Corchorus olitorius L. Cyperus difformis L., Dactyloctenium aegyptium (L.) Richt., Echinochloa phyllopogon (Stapf) Koss, Euphorbia heterophylla L., Kochia scoparia (L.) Schrad., Panictun capillare L., Solanum cornutum Lam, and S. elaeagnifolium Cav. They were possibly introduced with contaminated crop seeds. With the exception of S. cornutum , which has disappeared from the site where it was first collected in 1987, the other species are becoming major weeds in one or more provinces. Details of their biology and importance are discussed.     

Distribution, biology, and agricultural importance of Galinsoga parviflora (Asteraceae)

Galinsoga parviflora , an annual dicot species of the family Asteraceae, is a common herb that is often found in disturbed habitats and agricultural areas in many parts of the temperate and subtropical regions of the world. It is a native of tropical America and the center of its origin is thought to be the mountainous area of Central America. Galinsoga parviflora is considered to be a common weed in several crops of major importance, such as wheat, corn, cotton, tobacco, sugarbeet, tomato, pepper, potato, bean, onion, cabbage, garlic, coffee, citrus, banana, and strawberry; it is frequently found in gardens and uncultivated areas. It succeeds particularly in moist soils and it is favored by a long photoperiod and high light intensity. The significant features of the plant, such as the lack of seed dormancy, rapid growth and development, early flowering, many generations per growing season, production of a great number of seed in a wide range of environmental circumstances, and the ability for easy vegetative reproduction under favorable conditions predispose the plant to be a troublesome weed. These features allow the easy distribution and rapid establishment of the weed in large populations, a fact that often makes this weed difficult to control. Galinsoga parviflora competes strongly, particularly with irrigated crops of short height, and it might also hinder crop harvest. The management of G. parviflora can be achieved by manual weeding, repeated soil cultivation, crop rotation, mulching, and herbicide application. The plant is reported to be edible and is used also for medicinal purposes.     

Etude du stock en semences d'Echinochloa crus-galli (L.) Beauv. dans le sol des rizières du Gharb (Maroc)

Study of the seed stock of Echinochloa crus-galli (L.) Beauv. in the soil of rice-fields in Gharb (Morocco) Estimates of the numbers of viable caryopses of Echinochloa crus-galli were made on soil samples taken from twenty-six rice-fields in Gharb (Morocco). Fields were chosen according to three factors: soil type, rotation and number of years in rice. The mean value of the stock of E. crus-galli caryopses is 1285 m^?2 to 60 cm depth. Its mean contribution to the total seed stock is 7.2%. The sampling plan permitted analysis of soil effects on the rotation three rice: three alternative crops and of rotation on merja soil (this soil is characterized by the smallest stocks in rotations — three rice: three other crops and three rice crops: one other). The mean distribution of caryopses in the soil profile was 85%, 12.5% and 2.5% respectively in the 0–20, 20–40 and 40–60 cm horizons. Field emergence of seedlings of E. crus-galli. from harvest to the sowing of the following crop, represented 0.65% of the stock in the soil.     

Production and Germination of Oospores of Phytophthora infestans (Mont.) de Bary in Morocco

One hundred and eight isolates of Phytophthora infestans were collected from infected potato and tomato crops in the middle-north of Morocco during 1997–2000. Pairings of these isolates with tester isolates of mating type A1 and A2 revealed that 60% of the isolates were mating type A2 (65/108) and 40% were mating type A1. After 10 days incubation at 20 °C and a 16-h photoperiod, approximately 25% and 18% of the oospores produced in-vitro germinated in potato soil extract and potato root extract, respectively. Oospores were observed in potato leaf tissues in pairings that were fertile in-vitro. Maximum production of oospores was obtained in potato leaves of cultivars that were moderately susceptible (Desirée, Nicola) after 10 days of incubation at 15 °C and a 16-h photoperiod. These results confirm the presence of P. infestans strains that are sexually compatible under Moroccan climatic conditions. Production of oospores constitutes a threat for these crops because of the occurrence of recombinants with new virulences which may be difficult to control and as a consequence survival of oospores in absence of the host plant in the soil.     

Evolution des hydrates de carbone non structuraux chez la morelle jaune (Solatium elaeagnifolium Cav.)

Les teneurs en hydrates de carbone non structuraux (TNC) des racines, collets et tiges des in-dividus de la morelle jaune (Solarium elaeagnifolium Cav.) issue des bordures, champ de cotonnier et verger d'oliviers ont été déter-minées mensuellement pendant une année. Les racines et, dans une certaine mesure, les collets ont été les organes où les réserves glucidiques étaient les plus importantes. Ces glucides ont atteint leur niveau le plus bas au moment de la formation des boutons floraux. La reconstitution des réserves en TNC a lieu entre la floraison et la maturation des fruits sur une durée de 2, 4 et 5 mois pour les individus issus du champ de cotonnier, des bordures et du verger d'oliviers, respec-tivement. L'évolution des TNC est plus influencée par le stade phénologique de l'espèce que par rhumidité et la température du sol. Les implications de ces réquitals pour définir une stratégic de lutte centre la morelle jaune sont également discutées. Seasonal changes in non-structural carbohydrates in silver-leaf nightshade (Solanum elaeagnifolium Cav.) The levels of non-structural carbohydrates (TNC) in the roots, root collar and stems of S. elaeagnifolium collected from field margins, cotton fields and olive plantations were determined monthly over a period of 1 year. The roots, and to a certain extent the root collar, were the organs with the largest carbohydrate reserves. The carbohydrate level was lowest at the time of flower bud formation. There was a build-up of TNC reserves between flowering and fruit maturation over periods of 2, 4 and 5 months from plants growing in cotton fields, field margins and olive plantations respectively. Changes in TNC are influenced more by the phenological stage of the plant than by soil humidity or temperature. The implications of these findings in defining a control strategy for this weed are discussed. Saisonale Einlagerung von Kohlenwasserstoffen beim Ölweidenblättrigen Nachtschatten (Solanum eleagnifolium Cav.) Die Gehalte unstrukturierler Kohlenwasser-stoffe (TNC) des Wurzeln, des Wurzelhalses und des Sprosses von Solanum elaeagnifolium Cav. von Feldrainen, Baumwollfeldern und Olivengärten wurden monatlich über l Jahr hin bestimmt. Die Wurzeln und in bestimmten Maβe der Wurzelhals waren die Pflanzenteile, in denen die Kohlenwasserstoffe die wichtigsten Re-servesubstanzen waren; sie hatten ihr nie-drigstes Niveau zur Blütenbildung. Der Wiederaufbau dieser Reservestoffe zwischen der Blüte und der Fruchtreife dauerte bei den Pflanzen auf den Baumwollfeldern, den Feldrainen und den Olivengärten 2, 4 bzw. 5 Monate. Die Kohlenhydratbildung wurde mehrnach den Entwicklungsstadienals durch Boden feuchte und-temperatur beeinflußt. Die Aspekte dieserUntersuchungsergebnisse für die Bekämpfung dieses Unkrauts werden diskutiert.     

Effect of Slovenian climatic conditions on the development and survival of the root-knot nematode <Emphasis Type="Italic">Meloidogyne ethiopica</Emphasis>

Meloidogyne ethiopica is a tropical root-knot nematode species which has recently been found in Europe. We examined its ability to survive in open fields located in regions with sub-Mediterranean and continental European climates. The outdoor microplot experiment consisted of two locations and lasted three growing and two winter seasons. It was demonstrated that M. ethiopica was able to survive at both locations and also that it retained its infection ability although temperatures below zero were recorded. The correct species was confirmed after each winter season by isozyme electrophoresis. Furthermore, the influence of temperature on the reproduction cycle of M. ethiopica was investigated. Meloidogyne ethiopica required 67, 48 and 36 days to complete the reproduction cycle at mean daily temperatures of 18.3, 22.7 and 26.3°C, respectively. At 13.9°C, M. ethiopica was not able to reproduce. The data obtained from these experiments were used to develop a correlation between temperature and the time needed for M. ethiopica to complete a reproduction cycle using a mathematical equation. Furthermore, eight vegetable crops that are important for agricultural production in Slovenia were tested for their suitability as hosts for M. ethiopica.     

Host specificity of a brazilian isolate of<Emphasis Type="Italic">Alternaria cassiae</Emphasis> (Cenargen CG593) under greenhouse conditions

SeveralAlternaria cassiae isolates were recovered from diseased sicklepod plants (Senna obtusifolia) in the southern regions of Brazil. A representative isolate (Cenargen CG593) was tested for its host range under greenhouse conditions. The fungus promoted symptoms in sicklepod, cassava (Manihot dulce), tomato (Lycopersicon esculentum) and eggplant (Solanum melongena) when tested at a spore concentration of 10⁶ spores ml⁻¹. When the plants were inoculated with a suspension of 10⁵ spores ml⁻¹ and held at a dew period of 12 h (cassava) or 18 h (tomato and eggplant), the plants showed symptoms of the disease, but they recovered and continued their normal vegetative growth. These results show that the fungusA. cassiae is safe to use for the control ofS. obtusifolia under Brazilian conditions, because it did not cause excessive damage in the three plants tested. http://www.phytoparasitica.org posting Jan. 14, 2007.     

Comparaison de la germination et de la croissance de biotypes sensibles et résistants aux triazines chez quatre espèces de mauvaises herbes

Comparison of germination and growth of biotypes sensitive and resistant to triazines in four weed species. By observing germination under various conditions and plant development in non-competitive conditions, a comparison was made between sensitive and resistant biotypes of four species in which resistant populations have been discovered: Chenopodium album, Amaranthus retroflexus. Solanum nigrum and Polygonum lapathifolium. In spite of différent levels of significance, results indicate that the sensitive plants develop better. However, these findings may be modified according to the growth conditions. Moreover, high variance values in the characteristics measured reflect considerable heterogeneity at least in the sensitive lots. Nevertheless, seed from resistant plants of P. lapathifolium and, to a lesser extent, of Amaranthus, germinate more readily at low temperatures. In the light of these findings the authors discuss the possible advantages conferred on different lots by these characteristics, stressing the need to consider each species separately and to take into account the nature of the genotypes being compared. From such findings, while the exact factor determining resistance is not known, it is difficult to deduce a lower level of adaptability in resistant, as opposed to sensitive individuals, based on their place of origin and in the absence of herbicide treatments.     

First record of the invasive mite<Emphasis Type="Italic">Tetranychus evansi</Emphasis> in Greece

The red spider miteTetranychus evansi (Acari: Tetranychidae) Baker and Pritchard was recorded for the first time in Greece, in the area of Tympaki (south-central Crete) onSolanum nigrum. T. evansi is a pest of crops of the family Solanaceae, which are grown extensively in Crete. The species identification was based on both morphological and molecular data. The second internal transcribed spacer was PCR amplified and sequenced in samples from Crete. Sequences were compared with the sequence ofT. evansi from Brazil and with the ITS2 sequences (retrieved from GenBank) of the two closely related tetranychid species most commonly found in Greece,Tetranychus turkestan andTetranychus urticae.     

Etude de la compétition entre la morelle jaune (Solanum elaeagnifolium Cav.) et le maïs de printemps (Zea mays L.)*

La compétition entre la morelle jaune (Solanum elaeagnifolium Cav.) et le maïs (Zea mays L.) a étéétudiée au champ au cours de la saison 2001. Des durées de compétition avec la morelle jaune plus ou moins longues, tardives et précoces ont été imposées à la culture au cours du cycle. Les résultats montrent que les paramètres de croissance (hauteur, surface foliaire, matière sèche) du maïs ont été affectés par la présence de la mauvaise herbe. Plus la durée de compétition est longue, plus ces paramètres sont réduits. Les principales composantes du rendement, à savoir le nombre de grains/épi et le poids de 1000 grains ont été fortement influencées par la morelle jaune. Il en est de même pour le rendement global qui diminue d’autant plus que la compétition avec l’adventice dure longtemps. Ce dernier a été réduit de 64% en cas de non désherbage. Pour des pertes de rendements tolérées de 15%, la période critique de sensibilitéà la mauvaise herbe serait située entre le stade floraison de la culture et le stade grain laiteux avancé. La mauvaise herbe arrive à accomplir parfaitement son cycle biologique lorsque aucun désherbage n’est effectué. Des désherbages se poursuivant jusqu’au stade grain pâteux de la culture ont permis de réduire la production de fruits de la mauvaise herbe.