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.

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.

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.

Efficacy of mating disruption against Thaumatotibia (= Cryptophlebia) leucotreta (Lepidoptera: Tortricidae) in small cotton growing exploitations in Côte d'Ivoire ABSTRACTThe false codling moth Thaumatotibia leucotreta (Lepidoptera: Tortricidae) is a major cotton bollworm species in Côte d'Ivoire. This pest is not efficiently controlled by insecticide treatments and its infestations are keeping on rising since the last decade. In order to put in place an efficient management strategy a mating G.E. C. OCHOU et al. / Int. J. Biol. Chem. Sci. 11(3): 1222-1235, 2017 1223 disruption method was assessed with a pheromone formulation comprising 240 mg of attractive ingredients per disruptor (166,8 mg of E-8 -dodecenyl acetate + 70,8 mg of Z-8 -dodecenyl acetate + 2,4 mg of E/Z-8 -dodecenol). An experimental design at farm scale put in comparison non-treated and treated plots with different dosages of pheromone. The minimal dosages of 24 and 48 g a.i/ha reduced significantly for more than 4 months levels of natural populations of T. leucotreta as well as the attacked boll ratio and the level of larval infestations in bolls. Compared with non-treated plots, farm plots which received mating disruptors provided higher seed cotton yields. The present study enabled us to define the modalities of application of mating disruptors against T. leucotreta in small cotton growing exploitations in Côte d'Ivoire. The method appeared to be a novel mean to reinforce the actual phytosanitary program.

In recent years, an outbreak of Bemisia tabaci has been observed in Côte d'Ivoire in cotton crops despite the insecticide treatments. An evaluation of the sensitivity levels of insecticides commonly used for the protection of cotton trees has been undertaken in order to identify the most effective active ingredients against B. tabaci. Whitefly populations were collected in six (6) different localities in the cotton production area (Niakara, Bouaké, Ouangolo, Ferké, Boundiali and Korhogo). They were tested by the leaf dipping method with five (5) insecticides of different chemical families (Organophosphorus, Pyrethroids, Neonicotinoids, Sulfoximines, Spinosynes). LC50s for each insecticide were calculated using the probit-log model and compared using variability in insecticide susceptibility of B. tabaci populations and a significant difference between the levels of insect susceptibility to the insecticides tested. Strains from Korhogo showed the lowest susceptibility to profenofos (LC50=71.51 mg.l -1 ), and strains from Boundiali the lowest susceptibility to acetamiprid (LC50=219.96 mg.l -1 ). Acétamipride was significantly less toxic compared to lambdacyhalothrin and profenofos (F=2.58; P=0.04). Sulfoxaflor (LC50=0.71 mg.l -1 ) and spinosad (LC50=4.02 mg.l -1 ) were the most toxic products. This study, which is the first of its kind in Côte d'Ivoire, represents a database for the management of B. tabaci populations.