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.
Among the alternatives to environmentally toxic and socio-economically unacceptable chemical pesticides, essential oils from Ocimum gratissimum and Cymbopogon citratus were tested on the main pests and beneficial insects of the cotton plant in Côte d'Ivoire. After extraction and chemical analysis of the essential oils, field trials were carried out using a Fisher block system with three treatment repetitions where their effects compared with those of a registered synthetic insecticide (IBIS A 52 EC). Foliar applications of the products were carried out in accordance with the cotton plant protection extension programme in Côte d'Ivoire from the 45th to the 115th day after plant emergence, with one application every fortnight. Twenty-three and forty compounds representing about 96 and 99 % of the oil composition of O. gratissimum and C. citratus respectively were elucidated. The most abundant compounds were p-cymene and thymol (O. gratissimum) and myrcene, neral and geranial (C. citratus). The essential oil of O. gratissimum at concentrations of 2 and 5 % showed insecticidal activity on all pests (biting-sucking and carpophagous), except the phyllophagous Syllepte derogata. C. citratus, at a low concentration (1 %), was particularly toxic to whiteflies (Bemisia tabaci), however, it favoured the action of beneficial insects, specifically black ants and ladybirds in the cotton plots, unlike the chemical product. EO of O. gratissimum (1.60 and 4.62 mg GALAE/g, respectively) and C. citratus (2.26 and 2.78 mg GALAE, respectively) exhibited also significant acetyl and butyryl cholinesterase inhibitors. Insecticide formulations based on the essential oils of O. gratissimum and C. citratus offer favourable prospects for their use in cotton cultivation as an alternative to chemical pesticides.
The abusive and repeated use of synthetic chemical insecticides has proven to be harmful to human health and the viability of the cotton production system in Ivory Coast, so it is imperative to find alternatives. . Thus, the objective of this study was to study the chemical composition and biological activity of essential oils of Lippia multiflora (Verbenaceae) and Eucalyptus globulus (Myrtaceae) and to evaluate their insecticidal potential in the laboratory on three main pests of cotton. After essential oils extraction, their chemical composition was determined. Also, antioxidant activity and cholinesterase inhibitor of essential oils were evaluated. After that, different concentrations of the two essential oils were prepared and applied by contact on groups of insects constituted by ten. The essential oil of L. multiflora was the most toxic for the three pests tested. Indeed, the lethal concentrations (LC50) were 1.74 %, 1.39 and 7.20 %, respectively, on Pectinophora gossypiella, Thaumatotibia leucotreta and Helicoverpa armigera. In contrast, the values obtained with E. globulus essential oil were nine to two times greater (16.05 %, 10.23 % and 16.32 %, respectively on these pests). With respect to the chemical composition of the essential oils, E. globulus essential oil was the richest in oxygenated monoterpenes (65 %) with 1,8‐cineole or eucalyptol as the majority compound (61.6 %). The essential oil of L. multiflora was distinguished by a lower proportion of oxygenated monoterpenes (44.3 %), but it contained more terpene elements (24 vs. 15 for the essential oil of E. globulus). The essential oils of L. multiflora and E. globulus also showed significant inhibition of acetyl (2.13 and 2.16 mg galantamine equivalent (GALAE)/g, respectively) and butyryl cholinesterase (4.03 and 3.61 mg GALAE, respectively). L. multiflora was differentiated by its good inactivation of tyrosinases (163.46 versus 58.95 mg kojic acid equivalent (KAE)/g in E. globulus). Better antioxidant activity was observed with L. multiflora essential oil relative to DPPH (7.05±0.34 mg trolox equivalent (TE)/g). Biopesticides based on L. multiflora essential oil could be developed for the phytosanitary protection of cotton plant.
23 Diversité floristique en culture d'ananas (Ananas comosus (L.) Merr.) en basse Côte d'Ivoire INVENTAIRE DE LA FLORE ADVENTICE EN CULTURE D'ANANAS (Ananas comosus (L.) MERR.) DANS LA LOCALITE DE BONOUA EN BASSE CÔTE D'IVOIRE
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 European Scientific Journal July 2018 edition Vol.14, No.21 ISSN: 1857 -7881 (Print) e -ISSN 1857 218 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.Keywords: Pectinophora gossypiella, adult populations, larval infestations, geographic distribution, cotton. ResumeDans le but d'actualiser les connaissances sur l'évolution spatiotemporelle de Pectinophora gossypiella, l'aire géographique et la période de prédilection des populations adultes et larvaires ont été étudiées au cours des six dernières années de 2012 à 2017. L'étude a montré que les populations adultes sont plus abondantes dans la zone de production cotonnière du Sud par rapport à celle du Nord. Elles ont une très faible activité pendant l'intersaison alors que les pullulations les plus importants débutent du 22 Octobre au 17 Décembre. Le suivi des infestations larvaires sur un réseau de parcelles paysannes a montré que les infestations surviennent sur le cotonnier dès le début d'Août et s'accroissent jusqu'en Novembre. Ce qui induit une forte relation entre l'évolution des populations adultes, les infestations larvaires et la phénologie du cotonnier. Les semis tardifs D5 et D6 ont présenté des niveaux d'infestation plus importants (0,50 à 0,80 chenille/ 100 capsules) contre 0,21-0,31 chenilles/100 capsules pour les semis précoces. Les variations annuelles des niveaux moyens d'infestations ont augmenté d'années en années de 0,14 à 0,95 chenille/ 100 capsules sur la période d'étude. La cartographie de la distribution géographique des infestations a montré que la pression du ravageur est plus prononcée dans les...
RESUMELa cercosporiose et la cladosporiose sont les principales maladies observées dans les bananeraies de Côte d'Ivoire. Une étude comparée de ces deux maladies a été effectuée dans des conditions naturelles d'infestation sur les cultivars de bananiers Corne 1, Orishele et Grande Naine. Des inoculations ont été faites in vitro en vue de déterminer les périodes d'apparition des premiers symptômes de ces maladies et leur évolution et de les comparer à ceux observés au champ. Les paramètres PJFT, PJFN, PJF3 et PJFEN ont été suivis en plantation, de même que le comptage des périthèces sur les feuilles nécrosées. Les résultats montrent une sensibilité du cultivar Grande Naine avec apparition précoce de nécroses. Les périodes d'incubation et le cycle de la maladie ne sont pas significativement différents chez les 3 cultivars. L'apparition des premiers symptômes dépend du stade cigare de chaque bananier. La cladosporiose a été observé chez tous les cultivars. Les symptômes de stade 1 ont été observés sur les feuilles de rang 1 à 3 en fonction du stade cigare, mais n'ont pas évolué au delà. En conditions contrôlées, l'apparition précoce des symptômes de cercosporiose noire, par rapport à ceux de la cladosporiose, a été mise en évidence.
The Black Leaf Streak Disease (BLSD) is one of main parasitic constraints of the agro-industrial plantations of banana in the world. Caused by a fungus ascomycete (Mycosphaerella fijiensis Morelet), the losses of yield are up to 50 %, without of resistant cultivars and effective management. This study relative to the level of the disease has been conducted in 12 industrial plantation in 6 production area: Aboisso, GrandBassam, Dabou, Agboville, Azaguié and Tiassalé; for a total surface of 2576 ha. The observations concerned the ranks of Youngest Leaf Spotted (YLS), of the Youngest Leaf Necrosed (YLN), the Number of Standing Leaves (NSL) and the gap between the Youngest Leaf Spotted and the Number of Standing Leaves. The results showed that chronic re-infestation of industrial plantation during the last five years, except CDBCI Tiassalé-Songon in 2011 European Scientific Journal January 2016 edition vol.12, No.3 ISSN: 1857 -7881 (Print) e -ISSN 1857 38 and 2012. An acceptable level of re-infestation was observed in 2012 on other plantations, with the rank of YLS greater than or equal to 3, except BATIA Tiassalé and CDBCI Azaguié. The internal inoculum pressure (YLS) varied a lot from one plantation to another and from one year to another. Except plantation SBMK Aboisso and BATIA Tiassalé, other plantations had at least one value of the rank of the top YLS or equal to 8, during the study indicating a relatively low severity of the BLSD. RésuméLa maladie des raies noires (MRN) est une des principales contraintes parasitaires des plantations agro-industrielles de banane dessert dans le monde. Causée par un champignon ascomycète (Mycosphaerella fijiensis Morelet), les pertes de rendement dues à cette maladie foliaire peuvent dépasser 50 %, en absence de cultivars résistants et de lutte efficace. Cette étude, portant sur le niveau de la maladie, a été menée dans 12 plantations industrielles réparties en 6 bassins de production : Aboisso, Grand-Bassam, Dabou, Agboville, Azaguié et Tiassalé ; pour superficie totale 2576 ha. Les observations ont porté sur les rangs de plus jeune feuille touchée (PJFT), de la plus jeune feuille nécrosée (PJFN), le nombre de feuilles érigées (NFE), l'écart entre la plus jeune feuille touchée ( IntroductionLa maladie des raies noires (MRN) due au champignon Ascomycète (Mycosphaerella fijiensis Morelet) est la principale contrainte fongique affectant les bananiers après la reconversion variétale liée à la maladie de Panama (Lassoudière, 2012). En effet l'industrie bananière n'a dû son salut qu'au remplacement de la variété Gros Michel (sensible à l'agent causal de la maladie de Panama Fusarium oxysporum f. sp. cubense) par des variétés du groupe sinensis (Lassoudière, 2012). Initialement connue sous une forme dite jaune, relativement moins agressive (M. musicola Leach), la maladie des raies noires possède un spectre d'hôtes plus large puisqu'elle attaque avec succès les cultivars du groupe plantain, lesquels sont résistants à M. musicola (Fullerton, 1994). Elle est responsable de l...
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.
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