In Vitro and Molecular Docking Evaluation of Larvicidal Effects of Essential Oils of Five Aromatic Plants on the Fall Armyworm Spodoptera frugiperda JE. Smith (Lepidoptera: Noctuidae) from Ivory Coast.

Faced with the serious consequences resulting from the abusive and repeated use of synthetic chemicals, today rethinking crop protection is more than necessary. It is in this context that the essential oils of the Lamiaceae Ocimum gratissimum and Ocimum canum, the Poaceae Cymbopogon citratus and nardus and a Rutaceae Citrus sp. of known chemical compositions were experimented. The evaluation of the larvicidal potential of the essential oils was done by the method of topical application of the test solutions, on the L1-L2 stage larvae from the first generation of S. frugiperda obtained after rearing in an air-conditioned room. Lethal concentrations (LC10 , LC50 and LC90 ) were determined after 48 h. After assessing the larvicidal potential of essential oils, molecular docking was carried out to study protein-ligand interactions and their propensity to bind to insect enzyme sites (AChE). The essential oil of O. gratissimum was the most effective with the lowest lethal concentrations (LC10 =0.91 %, LC50 =1.91 % and LC90 =3.92 %). The least toxic oil to larvae was Citrus sp. (LC10 =5.44 %, LC50 =20.50 % and LC90 =77.41 %). Molecular docking revealed that p-cymene and thymol from O. gratissimum essential oil are structurally similar and bind to the AChE active site via predominantly hydrophobic interactions and a H-bond with Tyr374 in the case of thymol. The essential oil of O. gratissimum constitutes a potential candidate for the development of biological insecticides for the fight against insect pests and for the protection of the environment.

Application of Essential Oils of Ocimum gratissimum and Cymbopogon citratus as Bioinsecticides for the Management of Two Major Biting-Sucking Insects (Bemisia tabaci Gennadius and Jacobiella fascialis Jacobi) and the Improvement of Seed and Fiber Quality of Cotton Plants in Ivory Coast.

In recent years, in all cotton production areas in Ivory Coast, whitefly (Bemisia tabaci) and jassid (Jacobiella facialis), two biting sucker insects were causing depreciation of quality of the cottonseed and fiber obtained at harvest. However, the excessive use of synthetic chemical insecticides against these pests presents a danger for the sustainability of the production system. This study aims to evaluate the insecticidal efficacy of essential oils of Ocimum gratissimum and Cymbopogon citratus on B. tabaci and J. fascialis and on the technological parameters of the cottonseed and fiber. A field experiment was conducted in which essential oils of O. gratissimum and C. citratus were applied to cotton plants every two weeks from day 45 to 115 after emergence using a backpack sprayer. The effects of these extracts were compared to those of a synthetic chemical insecticide composed of acetamiprid and alphacypermethrin known under the trade name IBIS A 52 EC (positive control). After 160 days of cultivation where entomological data were collected, the seed cotton samples were harvested, ginned and submitted for analysis. O. gratissimum essential oil at concentrations of 1 and 5 % gave to the cotton plants better protection against whiteflies and jassids. In addition to the synthetic chemical, these cotton plants received a better proportion of healthy cottonseed, fat and a fiber with very good reflectivity. The essential oil of O. gratissimum could therefore be integrated into the phytosanitary protection programs of the cotton plant.