Published online by Cambridge University Press: 19 September 2011
Bioassays were carried out in Petri dishes with body washings of larvae, male and female moths and scale extract of Corcyra cephalonica St. in hexane to observe their kairomonal effect on Trichogramma brasiliensis (Ashmead) and T. japonicum Ashmead. The mean parasitoid activity index (PAI) and mean parasitisation were recorded. Trichogramma brasiliensis and T. japonicum recorded the highest mean parasitisation in the eggs treated with scale extract. Mean parasitisation recorded by T. japonicum in cards treated with female moth and male moth body washings were considerably lower than the corresponding values for T. brasiliensis. Both the parasitoids recorded significantly lower levels of parasitisation in cards treated with larval body washings. Gas chromatographs of host body washings / extract recorded a large number of similar hydrocarbons in the body washings of male and female moths and the scale extract. Pentadecane, heneicosane, eicosane, tetracosane, pentacosane and hexacosane were recorded in scale extracts. Female moth body washings recorded the presence of eicosane, tetracosane and pentacosane while heneicosane and eicosane were indicated in the male moth body washings.
Des essais biologiques de laboratoire ont été menés par rinçages à l'hexane du corps des larves, des adultes mâles et femelles, ainsi que par l'extrait d'écailles de Corcyra cephalonica St., afin d'observer leurs effets kéromonaux sur Trichogramma brasiliensis (Ashmead) et T. japonicum Ashmead. L'index d'activité moyenne du parasitoïde (IAP) ainsi que la moyenne de parasitisme étaient notés. La moyenne la plus élevée de parasitisme a été observée chez T. brasiliensis et T. japonicum sur les oeufs traités aux extraits d'écaillés. La moyenne de parasitisme observée chez T. japonicum sur les cartes traitées au moyen des rinçures du corps des adultes mâles et femelles était considérablement très basse en comparaison des valeurs correspondantes enregistrées pour T. brasiliensis. Pour tous les deux parasitoïdes, les niveaux de parasitisme étaient bas dans le cas des cartes traitées au moyen des rinçures corporelles obtenues des larves. Les chromatographies à phase gazeuse des rinçures corporelles / extrait de l'hôte ont révélé la présence d'une large gamme d'hydrocarbonates similaires dans les rinçures des adultes mâles et femelles, de même que dans l'extrait d'écaillés. La pentadécane, l'hénéicosane, l'éicosane et l'hexacosane étaient obtenues dans les extraits d'écaillés. Les rinçures du corps de la femelle ont témoigné de la présence de l'éicosane, la tetracosane et de la pentacosane randis les rinçures du mâle ont révélé la présence de l'hénéicosane et de l'éicosane.
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