Published online by Cambridge University Press: 19 September 2011
Different concentrations of essential oil of lemon grass, Cymbopogen citratus, were tested for their ovipositional inhibition, antifeedant activity and insecticidal properties against the lesser cotton leafworm, Spodoptera exigua. The results obtained showed that 2% concentration of oil emulsion inhibited egg laying and 0.5% concentration more than reducted by 70% the number of eggs deposited on oviposition sites. 2% concentration acts as a protective concentration against the immature stage by hindering the third instar larvae to feed on treated leaf discs. In addition, the oil emulsion was insecticidal in that percentage mortality was directly proportional to the concentration applied and to the duration of exposure. Older egg masses were more affected by treatment than the newly laid eggs. 2% concentration inhibited hatchability when sprayed on egg masses before hatching. Lemon grass oil effectively controlled S. exigua as an ovicidal and larvicidal agent.
Differents concentrations des huiles essentieles de C. citratus ont été testé comme inhibiteur d'ouiposition at l'actináté anti-alimentaire contre S. exigua. Les resutats ont montrè une inhibition de la mise d'aeufs lars d'un traitment par 2% dl'huil. Le traitment des sites d'oviposition par 5% a reduit le nombre d'aeufs jusqua 70% par contre le traitment par une concentration de 2% peut etre protectif contre les stades immatures. L'effet martel del'hiul de C. citratus est proportiannel á la concentration appliquée et la durée d'exposition.