Evolution spatiale et temporelle des dégâts du jasside Jacobiella facialis Jacobi, 1912 (Cicadellidae) Mots clés : Jasside, pluviométrie, évolution spatio-temporelle, cotonnier, protection, Côte d'Ivoire. KONE et al. / Int. J. Biol. Chem. Sci. 11(3): 1190-1201, 2017 1191 Spatial and temporal variation of the injury levels of jassid Jacobiella facialis Jacobi, 1912 (Cicadellidae) in relation to rainfall variation for the last two decades in the cotton growing area of Côte d'Ivoire ABSTRACT Jassid Jacobiella facialis is a sucking pest of cotton in Côte d'Ivoire. For the last decades, its attacks are persistent throughout the entire crop cycle despite insecticide treatments. This study aimed at analyzing the spatial and temporal distributions of pest damage in relation to rainfall trends over the past two decades. From 1993 to 2015, pest and rainfall surveys were carried out through a network involving more than 300 fields. Data revealed an annual variation in the pest damage levels, fluctuating between 0.52 and 6.01 attacked plants for 30 explains significantly the resurgence of the pest. In fact, the distribution of high pest pressure in the Northeast corresponds, during the last decade, particularly to rainfalls lower than 320 mm. This suggests the development of a new strategy for effective management of J. facialis. P. W. E.

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.

Objective: The study of the spatio-temporal evolution of the infestations of whitefly Bemisia tabaci (Aleyrodidae) aims to acquire bioecological data exploitable in the fight against the whitefly in cotton growing of Cote d'Ivoire. Methodology and results: Average levels of infestation (NMI) were estimated from 2003 to 2015 for the entire North and South zones of cotton production. Ten (10) cotton producer plots were randomly selected by locality. The number of adult insects per plot was counted on a sample of 30 plants. These weekly surveys revealed seasonal, spatial and annual variations in B. tabaci infestations. The results showed a proliferation of B. tabaci in cotton growing in Côte d'Ivoire. B. tabaci is present from the beginning to the end of the cotton growing cycle. Strong B. tabaci outbreaks occur on average from the 96th day after seedling emergence (DAS). June cotton seedlings are heavily exposed. The insect showed a strong presence in the northeast of the cotton zone. Conclusion and application : The phytosanitary protection programs for cotton appear to have a low control of B. tabaci. A revision of the phytosanitary protection strategy for cotton is therefore necessary. Insecticidal leaf treatments carried out from the 30 th to the 45 th DAS will have to integrate aleurodicidal products in order to limit the proliferation of whiteflies at the beginning of cultivation, especially in the northeast zone. Synchronized seedlings in an area would prevent the transfer of insects to younger plants and thus greatly reduce B. tabaci infestation levels.

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.

Jacobiella facialis is a sucking insect pest of cotton in Côte d'Ivoire. Heavy infestations on cotton resulted in shedding of leaves, squares, young bolls and subsequently lead to significant yield losses. In recent years, attacks of the jassid remain persistent throughout the entire crop cycle despite insecticide treatments. Susceptibility tests of ten (10) active ingredients (chlorpyrifos-ethyl, profenofos, acetamiprid, imidacloprid, alpha-cypermethrin, lambdacyhalothrin, spinoteram, sulfoxaflor, spinosad and chlorantraniliprole) were performed against pest populations collected in Bouaké by leaf-dip method n° 15 proposed by Insecticide Resistance Action Commitee (IRAC 15, version 3). Lethal concentrations LC50 and LC90 were determined for all active ingredients. To compare susceptibility between different field strains, discriminate concentrations (LC90) for the most toxic active ingredients were tested by the same method on jassid populations from five localities (Korhogo, Boundiali, Ferké, Ouangolo and Niakara). Five active ingredients, chlorpyrifos-ethyl, profenofos, acetamiprid, alpha-cypermethrin and imidacloprid, with respective lethal concentrations (LC50) of 0.0012, 0.011, 0.024, 0.057, 0.070 mg/ml, were the most toxic to jassid, while spinosad and chlorantraniliprole were the least toxic as LC50 values were 1.616 mg/ml and 5.4 mg/ml respectively. Data collected on discriminate concentrations (LC90) for four active ingredients did not revealed any significant difference between the susceptibility levels of jassid strains. However, it was noted that survival rates were consistently high in strain collected from Boundiali and Korhogo, indicating low heterogeneity within some field populations. The results have provided important information on active ingredients to consider when developing pest management programs.

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...

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.