Rice weevil (Sitophilus oryzae L.) is a primary insect pest of stored grain. The development of resistance resulted in the application of synthetic insecticides. In recent years many plant essential oils have provided potential alternatives to currently used insect control agents. The Brazilian pepper tree (Schinus molle L. var. areira (L.) DC.) (Anacardiaceae) ) (Anacardiaceae) has different biological properties such as insecticidal activity. In this study, repellent, fumigant activity, nutritional indices, and feeding deterrent action were evaluated on S. oryzae adults. Filter paper impregnation was used to test fumigant toxicity, whereas treated whole wheat was used to evaluate repellent activity and a flour disk bioassay was done to evaluate feeding deterrent action and nutritional index alteration. Leaf essential oils showed repellent effects at both concentrations (0.04 and 0.4% w/w), while fruit essential oils lacked repellent activity. Both plant oils altered nutritional indices. Fruit essential oils had a strong feeding deterrent action (62%) while leaves had a slight effect (40.6%). With respect to fumigant activity, neither of the essential oils was found to be toxic. Resistance and toxicity problems of the synthetic insecticides have resulted in the necessity of finding more effective and healthier alternatives. Thus, essential oils are the most tested products presently (Papachristos and Stamopoulus, 2002; Umoetok and Gerard, 2003; Zhang et al., 2004; Tapondjou et al., 2005; Ferrero et al., 2006; Sánchez Chopa et al., 2006, Stefanazzi et al., 2006, Wang et al., 2006. Different biological activities of plant derivatives have been demonstrated for the control of stored grain pests (Golob et al., 1999; Rajendran and Sriranjini, 2008).The Brazilian pepper tree (Schinus molle L. var. areira (L.) DC.) is associated with agricultural crops in boundaries, windbreaks, riverbank protection, and watershed conservation. In popular medicine, it is use for its astringent, diuretic, antispasmodic properties among others. In pest control, it is used as a fumigant, repellent, and ovicide (Ruffínengo et al., 2005; Ferrero et al., 2006).The objective of the present study was to evaluate the fumigant, repellent and/or attractant, feeding deterrent activity, and the alterations in the nutritional physiology produced by the essential oils from leaves and fruits of S. molle var. areira on 3-to 4-day-old S. oryzae adults.
V. BENZI et al. -BIOLOGICAL ACTIVITY OF ESSENTIAL OILS…
MATERIALS AND METHODS
InsectsThe insects came from a susceptible colony maintained in the Cátedra de Zoología Agrícola de la Universidad Nacional de Buenos Aires (UBA). They were bred in glass containers, 8 cm in diameter, 13 cm high, sealed with fine netting, maintained at 28 ± 1 ºC, 60-70% HR, a 12:12 photoperiod, and using whole wheat grains as food.
Vegetal materialThe vegetal organs (leaves and mature fruits) of the pepper tree were collected during the summer period in Bahía Blanca city, Buenos Aires, Argentina (38°41' S; 62°17' ...
