Caractérisation des insectes et des champignons infestant les fèves de cacao dans les principales zones de production en Côte d’Ivoire

If the culture of the cocoa in Côte d’Ivoire gives a great satisfaction concerning the production level, the quality of raw cocoa beans remains to be improved. One of the causes of this depreciation is the moulds development in beans. In order to identify responsible fungus, cocoa beens have been collected in the maine production areas which are the East, the Mid-West and the South-West, represented respectively by the localities of Abengourou, Oumé and Soubré. From collected beans, the fungus have been insulated and purified on PDA medium and then, they have been identified by observing their morphocultural and microscopic characteristics. The results show that 9 mushroom species belonging to 5 genera were identified in cocoa beans collected in the whole of the localities. There are Aspergillus, Penicillium, Fusarium, Curvularia and Streptomyces. Among them, the Aspergillus genus which is able to produce ochratoxine, was found with an appearance frequency of 86.30 %

EFFETS DU LIT ET DE LA DENSITÉ DE PLANTATION SUR LA CROISSANCE VÉGÉTATIVE DE L’ANANAS (ANANAS COMOSUS L., VAR. MD2) DANS LA LOCALITÉ DE DABOU EN CÔTE D’IVOIRE

The aim of this study was to identify the best planting bed and density for vegetative growth of Ananas comosus L. var. MD2 plants in the locality of Dabou in Côte d’Ivoire. The effects of three planting beds : flat land, ridge without polyethylene film and ridge covered with polyethylene film ; and two planting densities : 50,000 and 70,000 plants/ha (D50 and D70, respectively) were tested through a split-plot disposition. At the end of the vegetative phase of the cycle, growth parameters were evaluated. The results showed that D70, average heights apical bunches were higher (91.52 cm) than D50 (86.87 cm). The number of fresh leaves varied between 48 and 51. The ridge covered with polyethylene film was distinguished with a number of relatively larger fresh leaves. The follow-up of the D leaves biomass revealed that seven months, the value of 70 g required to trigger floral induction therapy (FIT) had been reached in all plants, whatever planting bed and density. The flat land - density 70,000 plants/ha combinaison was illustrated with the D leaves biomass the highest (80.20 g). The weight of the fruit beingrelated to the plant’s growth during the floral induction therapy, at the end of the vegetative phase, the results could contribute to improving the production of MD2 pineapple in locality of Dabou

Comparaison du potentiel insecticide des huiles essentielles de Ocimum gratissimum L. et de Ocimum canum Sims sur Pectinophora gossypiella Saunders (Lepidoptera : Gelechiidae), insecte ravageur du cotonnier en Côte d’Ivoire

The abusive use of synthetic pesticides in the phytosanitary protection of cotton in Côte d'Ivoire threatens the viability of the production system. The search for alternative control methods is therefore necessary. Phytosanitary strategies involving plant-based biopesticides have been explored. The insecticidal activity of essential oils of plant species of the genus Ocimum has been the subject of numerous investigations. The objective of this study is to compare the insecticidal potential of two species of the same genus Ocimum gratissimum and O. canum on a major cotton pest, the pink worm Pectinophora gossypiella. Adults of the insect were exposed in the laboratory to the toxic effect of different concentrations of these oils by topical application using a micro applicator. The lethal concentrations causing respectively 50 % (LC50) and 90% (LC90) death in the populations tested were determined for each of the essential oils. The oil extracted from O. gratissimum was the most toxic with LC50 and LC90 respective values of 1.01 % and 5.05 % as compared to O. canum (LC50 = 11.33 % and LC90= 30.04 %). The high toxicity of O. gratissimum may be explained by the presence of 24.57 % thymol and 37.79 % p-cimene in its chemical composition. The extract of O. gratissimum has shown in laboratory the highest potentiel insecticidal activity, it‘s field use can therefore be suggested for the control of this cotton pest

Caractéristiques de l’évolution spatio-temporelle de Pectinophora gossypiella Saunders (Lepidoptera : Gelechiidae) dans les zones de production cotonnière de Côte d’Ivoire : Implications pour une stratégie de gestion optimale de la résistance aux pyréthrinoïdes

In order to update knowledge on the spatio-temporal evolution of Pectinophora gossypiella, the geographical areas and the seasons of predilection of adult and larval populations have been studied in the last six years from 2012 to 2017. The study showed that adult populations are more abundant in the cotton production area of the South compared to the North. They have a very low activity during the intercropping season while the most important outbreaks occurred in October-December. The monitoring of larval populations carried out on farm scale showed that infestations started on cotton early August and increased until November, which leads to a strong relationship between the evolution of adult populations, larval infestations and cotton plant phenology. Late sowings D5 and D6 exhibited higher levels of infestation (0.50 to 0.80 larvae/100 bolls) as compared to early sowing (0.21-0.31 larvae/100 bolls). Annual variations of pest infestation levels increased from years to years, fluctuating from 0.14 to 0.95 larvae/100 bolls over the study period. Mapping of the geographic distribution of infestation showed more severe pest pressure in the southern cotton areas, mostly in surrounding areas of Bouaké, Bouaflé, Séguéla and Boron (18,90; 5,33; 1,52; 1,06 larvae/100 bolls respectively). With regard to the emerging status of P. gossypiella over recent years, the current pyrethroid resistance management strategy deserves to be improved on the basis of the pest geographic and seasonal profiles

Caractéristiques de l’évolution spatio-temporelle de Thaumatotibia leucotreta Meyrick (Lepidoptera : Tortricidae) dans les zones de production cotonnière de Côte d’Ivoire

In order to update knowledge on the spatio-temporal evolution of Thaumatotibia leucotreta, the geographical areas and seasons of predilection of adult and larval populations have been studied in the last six years from 2012 to 2017. Monitoring of natural adult populations revealed that populations were more abundant in the southern cotton production area as compared to the north. A Monitoring of larval infestations showed that infestations occurred on cotton at the end of august (0.10 larvae/100 bolls) and increased gradually during october-november (0.31 to 0.93 larvae/100 bolls), indicating a strong relationship between evolution of adult and larval populations and cotton phenology. Early sowings exhibited higher infestation levels (0.87 larvae/100 bolls). Annual variations of pest infestation levels increased from years to years, from 0.23 to 0.49 larvae/100 bolls over the study period. Mapping the geographic distribution of infestations showed highest pest densities in the southern zone, mostly in surrounding areas of Boron (1.52 larvae/100 bolls). With regard to the emerging status of T. leucotreta over recent years, the current pyrethroid resistance management strategy deserves to be improved on the basis of the pest geographic and seasonal profiles

PLANTAIN TREE GROWTH (MUSA SP., AAB CULTIVAR HORN 1) MODELING USING THE ARTIFICIAL NEURAL NETWORKS METHOD

The plantain tree growth is made up of a number of growth parameters such as leaves number (Ln), leaf length (Ll), leaf width (Lw), pseudo-stem height (Hp), width at 10 cm above the ground (W10), pseudo-stem width at middle (Wm) and its width at top (Wt). A study of these growth parameters was carried out in the area of Azaguié (Côte d'Ivoire). The results show that plantain tree growth depends on growth parameters evolution. For this purpose, mathematical models were developed to predict the growth using an artificial neural network. Satisfactory results were obtained since all the determination coefficients were higher than 0.97. These coefficients are approximately 1, and it points out the ability of the artificial neural network to map suitably the experimental data

Study of the Influence of Previous Vegetation and the Induction of Immunization of Oil Palm (Elaeis guineensis) against Fusarium Wilt

Study Design: One of the major challenges in the control of oil palm Fusarium wilt at prenursery stage for seedlings protection by pre-inoculation with a saprophytic strain of Fusarium oxysporum lies in the persistence of the defence induced under a high parasitic strain‘s pressure characterizing old oil palm plantations areas at replanting.Place and Duration of Study: Prenursery area of the National Center for Agronomic Research (CNRA), research station Robert Michaux of Dabou and oil Palm Physiology and Pathology Laboratory, between October 2009 and May 2010.Methodology: The assessment of the influence of the Fusarium wilt history of an oil palm plantation on the acquisition of protection by the next generation of oil palms was performed on 2-months-old oil palm seedlings, sensitive to Fusarium wilt and growing on three types of soils characterizing the different Fusarium wilt history.Results: The protection inducing treatment, characterized by the pre-inoculation of the non-pathogenic strain of Fusarium oxysporum (Fot) in the root system before the inoculation of the pathogenic strain F. oxysporum f. sp. elaeidis (Foe), has reduced the number of diseased seedlings at a rate of 24% against 35% when only the pathogenic strain Foe was inoculated in the seedlings, independently of the type of soil. Nevertheless, the expression of Fusarium wilt was delayed for a few weeks, only on the extension soil, and only in the case of pre-inoculation with Fot.Conclusion: The biological control of oil palm Fusarium wilt at prenursery stage can only be, for the moment and under the conditions specified herein, rationally envisaged in new areas and not in replanting of old oil palms’ areas

Effects of Two Cover Crops [Arachis Repens (L.) Handro And Desmodium Adscendens (SW.) DC.] on The Density of Arbuscular Mycorrhizal Fungi in Soils Under Industrial Banana Plantations in Côte d'Ivoire

This study aims to evaluate the effects of two leguminous plants Arachis repens and Desmodium adscendens, used as cover crops, on the proliferation of arbuscular mycorrhizal (AM) fungal spores in soils under industrial banana plantations. Soil samples were collected at two depths (0-10 cm and 10-20 cm) before, 6 and 12 months after the cover crops installation in a three-treatment Fisher block design. After laboratory analysis of the collected soil samples, the results showed that A. repens strongly contributed to the increase of AM fungal spores. Indeed, before planting this legume, the average number of spores which was 882.50 at 0-10 cm of the soil, increased to 1502.50 and then to 2390.00 in 100 g of soil respectively after 6 and 12 months. At the depth of 10-20 cm, the number of spores was 790.00, 1177.50 and 1270 spores/100 g soil, respectively. Acaulospora, Gigaspora, Glomus and Scutellospora were the main genus obtained among the identified spores. Among them, Glomus and Acaulospora were the most abundant. A. repens could be used as a cover crops for the sustainable management of biological soil fertility