Abstract
Cotton production is one of the main sources of income for the population and contributes to the socio-economic development in the northern and central areas of C??te d'Ivoire. However, cotton crop is subject to large and diversified pest problems, including jassids. Heavy infestations of jassids are likely to induce the stopping of plant development or the shedding of reproductive organs. For the last decade, there has been an increase and persistence of leafhopper attacks throughout the crop cycle despite insecticide treatments. This study aims to determine the biochemical mechanism likely to be involved in insecticide susceptibility of jassids. A biochemical assay of enzyme activities was performed on adult populations of jassids collected from cotton fields in six different localities (Bouak??, Korhogo, Boundiali, Ferk??, Ouangolo and Niakara) within the cotton growing area of C??te d??Ivoire. The method of Brogdon et al. (1997) was adopted with minor modifications. Alpha-esterase activity values ranged from 380.334 to 965.775 nmol ?ñ-naphtol/min/mg protein for Bouak?? and Ouangolo respectively. Beta-esterase activity ranged from 398.640 nmol ?ý-naphtol/min/mg protein for Bouak?? to 1,528.885 nmol ?ý-naphtol/min/mg protein for Ouangolo. Oxidase activity ranged from 0.016 nmol P450 EU/mg protein for Ferk?? to 0.038 nmol P450 EU/mg protein for Ouangolo. Glutathione-??-transferases varied between 0.554 nmol GSH conj/min/mg protein for Ferk?? and 1.128 nmol GSH conj/min/mg protein for Niakara. The involvement of ?ñ-esterases and ?ý-esterases in controlling the sensitivity level of jassids to active ingredients is thus highlighted. This observation suggests a rational selection of the active ingredients used to control these pests.
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