These results showed that the essential oils from T. terniflora, C. citratus and E. muticus should be studied further for their use in integrated pest management programmes for T. castaneum and S. oryzae control.

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' ...

The physicochemical characterization and residual insecticidal activity of poly(ethylene glycol) (PEG) nanoparticles containing essential oils (EOs) from geranium (Geranium sp.) and bergamot (Citrus reticulata L.) were evaluated against Blatella germanica for 1 year. The nanoparticles' size increased during the storage time from \235 to \450 nm; the EO content decreased approximately 50 %, and the abundance of the major components did not show any differences between pre-and post-formulation. The surface characteristics of nanoparticles were analyzed by transmission electronic microscopy. The EO nanoparticles produced a notable increase in the residual contact toxicity apparently because of the slow and persistent release of the active terpenes. In addition, the nanoformulation enhanced the EO contact toxicity. The results indicate that these novel systems could be developed as control agents against German cockroaches.

The human head louse, Pediculus humanus capitis (Anoplura: Pediculidae), is an ectoparasite confined to the scalp and human hairs. The repeated use of insecticides for the control of head lice during past decades has resulted in the development of marked levels of resistance. Natural compounds such as essential oils (EOs) have been suggested as alternative sources for insect control agents. In order to introduce a new pediculicide based on EOs, the effectiveness of the product and their effects on human being must be analyzed. In consequence, the biological activity of EOs from the leaves and fruits of Schinus areira (Anacardiaceae) and the leaves of Thymus vulgaris (Lamiaceae), Aloysia polystachya and Aloysia citriodora (Verbenacea) were evaluated against the eggs and adults of P. humanus capitis by fumigant and contact toxicity bioassays. Additionally, dermal corrosion/irritation tests were performed on New Zealand albino rabbits. In a fumigant bioassay, EOs from the leaves and fruits of S. areira were the most toxic against P. humanus capitis adults while these EOs and T. vulgaris were the most effective against the eggs. In contact bioassay, the EO from T. vulgaris was the most toxic against both stages. In the corrosion/irritation tests, the EOs did not produce dermal effects. According to the results, the essential oils from the leaves of T. vulgaris would be a valid tool for the management of P. humanus capitis. This EO produces a high knockdown effect in adults (followed by mortality) and toxicity in the eggs when it is applied for 21 min at a low concentration.

The human head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), is a worldwide public health concern. This human obligate ectoparasite usually infests school age children. The aim of this work was to investigate the prevalence of head lice in kindergarten children from Bahia Blanca. In addition, the influence of risk factors for pediculosis infestation, such as gender, hair characteristics, and socioeconomic class, was studied in relation to the prevalence of this ectoparasite. From a total of 220 pupils examined (125 girls and 95 boys), 94 showed pediculosis. The overall prevalence of head lice infestation was 42.7 %. Pediculosis was more frequent in girls (53.6 %) than in boys (28.4 %) and in medium, long, and very long hairs. No differences were found between socioeconomic classes. This indicated that head lice are relatively common in kindergarten children from Bahía Blanca.

One of the most common insect pests is Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae), which affects different food commodities. A new effective approach for the management of insect pests is the development of new formulations based on essential oils (EO). However, few works informed about the relationship between insecticidal activity of EO or essential oils loaded polymeric nanoparticles (EOPN) and post-application temperature. In our work, palmarosa [Cymbopogon martinii (Roxb.) Watson], geranium (Geranium maculatum L.), and peppermint (Mentha piperita L.) oils were formulated in a polyethylene glycol 6000 matrix to obtain EOPN. Geranium and palmarosa EOPN had sizes of 259 and 191 nm, respectively; the encapsulation efficiency (EE) was close to 90%, and the samples were monodisperse. The sizes from peppermint EOPN were around 380 nm, with an EE of 72%, and were polidisperse. In a contact toxicity bioassay, the insecticidal effect of the oils was increased by all EOPN, with palmarosa oil being the most toxic. In addition, the oils and their nanoparticles showed a significantly negative temperature coefficient when applied by contact. In a fumigant bioassay, just palmarosa and peppermint EOPN enhanced the oil activity and palmarosa EO and EOPN showed the highest toxic effect. In this case, the EO and EOPN insecticidal activity was unaffected by environmental temperature variation.

As part of a screening program to evaluate the biological activity of indigenous plants, we report the composition and the bioactivity of essential oils (EOs) extracted from Té de Burro Aloysia polystachya [(Griseb.) Moldenke] and Lemon Verbena Aloysia citriodora [Palau] against two of the most widespread secondary pests of stored products, the red flour beetle Tribolium castaneum [Herbst] and the confused flour beetle Tribolium confusum [Jacqueline du Val]. Analysis by gas chromatography-mass spectrometry of the EOs led the identification of their major constituents and their relative proportions. EO of A. citriodora showed the highest repellent activity against both beetles (>70%). On the other hand, both plants showed fumigant toxicity only against T. confusum, without significant differences between them (LC 50 values of 5.92 and 5.53 mg/L air for A. polystachya and A. citriodora, resp.). For contact toxicity (topical applications) the EO of A. polystachya was more effective (LD 50 = 7.35 g/insect) than the EO of A. citriodora (LD 50 = 13.8 g/insect) only against T. castaneum. On the other hand, T. confusum was not susceptible by contact to any of these EOs. These results provide important tools for the development of an Integrated Pest Management (IPM) program.

This study assessed the acute toxicity and repellence as well as feeding deterrence effect of volcanic ash (VA) on Sitophilus oryzae adults under laboratory conditions. VA resulted in significant adult mortality of S. oryzae. Acute toxicity of the VA was similar to that of commercially available diatomaceous earth DiatomiD ® demonstrating its insecticidal potential. Median lethal concentration values (LC 50 ) obtained were 1610 [1449, 1778] mg/kg for VA and 1046 [916, 1168] mg/kg for DiatomiD ® .Similarly to other inert dusts, VA particle size shows a bi-modal distribution and porosity which increases its surface area. Among the smallest particles, the highest volumetric loading was close to 5 µm with a distribution of smaller particles peaking at 0.5µm. Results indicate that VA is not repellent to S. oryzae. An "engagement" response or increased interaction of the insects with the VA treated surface was observed. However, feeding deterrence indices showed that both VA and diatomaceous earth had strong feeding deterrent action. Contact of insects with VA may lead to mortality by adherence of the VA particles to the insect cuticle. However, insects prefer feeding on sites without VA covered substrates and this could have a positive impact on its use for pest management.