Depressions of Dermestes maculatus (Coleoptera: Dermestidae) on Bones Could be Pupation Chambers.

Dermestes maculatus DeGeer beetles feed and can leave marks on bones. This species is of medical, veterinary, and forensic importance. The aim of this work was to determine if the depressions produced on bones by these beetles could be product of pupation. We studied under controlled conditions the behavior of D. maculatus larvae maintained at 24°C ± 3°C, 52.7% average relative humidity, and a 12:12-hour light/dark cycle and fed on pig carcasses. Observations were made, and photographs were taken. The results indicated that depressions produced by D. maculatus were consequence of feeding or pupation. This is the first time that pupation chambers on bones are confirmed.

The potential application of plant essential oils to control Pediculus humanus capitis (Anoplura: Pediculidae).

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.

Design and development of aqueous nanoformulations for mosquito control.

Microemulsions (ME) are thermodynamically stable isotropic mixtures of oil, water, and surfactant; they would also be attractive as potential insecticidal products due to the high bioviability of the active ingredient, attributable to the small sizes of the oil drops. A laboratory study was conducted in order to compare the biological effect of oil in water (o/w) geranium essential oil (EO) and geraniol MEs and emulsions, against Culex pipiens pipiens mosquito larvae. The systems were based on three nonionic surfactants (Cremophor EL, Brij 35, Tween 80). The MEs showed dispersed phase diameters in the range of 8 to 14 nm and had low PDI values (<0.2). The MEs were analyzed by TEM, indicating that they had nearly spherical morphology. The microemulsified systems based on geranium EO and those of geraniol produced a notable increase of the larvicidal activity when compared with the respectably emulsions, concluding that the biological effect is related with the diameter of the dispersed phase. The smallest drops achieved the highest larvicidal activity, being the aqueous nanoformulations based on geraniol most effective than those of geranium EO. However, geranium microemulsions are preferred due to their residual toxicological profiles. The results indicate that these novel systems could be used in integrated pest management program for the C. pipiens pipiens.

Prevalence of Pediculus humanus capitis infestation among kindergarten children in Bahía Blanca city, Argentina.

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.

Polymer nanoparticles containing essential oils: new options for mosquito control.

Mosquitoes (Diptera: Culicidae) are vectors of important parasites and pathogens causing death, poverty and social disability worldwide. The overuse of synthetic insecticides to control mosquito vectors lead to resistance, adverse environmental effects and high operational costs. Therefore, the development of eco-friendly control tools is an important public health challenge. In this study, two different essential oils (EO) (geranium, Geranium maculatum, and bergamot, Citrus bergamia) loaded polymeric nanoparticle (PN) were elaborated using polyethylene glycol (PEG) and chitosan (Qx) as the polymeric matrix/coating. In addition, the mosquito larvicidal acute and residual activity of the PN was evaluated on Culex pipiens pipiens. The physicochemical characterization of PN revealed that PEG-PN had sizes <255 nm and encapsulation efficiency between 68 and 77%; Qx-PN showed sizes <535 nm and encapsulation efficiency between 22 and 38%. From the toxicological test, it was observed that Qx-PN produced higher acute and residual activity than PEG-PN. Overall, this study highlights that polymer nanoparticles containing essential oil are a promising source of eco-friendly mosquito larvicidal products.

Essential oils nanoformulations for stored-product pest control - characterization and biological properties.

The lethal and sublethal activity of poly(ethylene glycol) (PEG) nanoparticles containing essential oils (EO), also the physicochemical characterization, were determined against Tribolium castaneum and Rhizopertha dominica. The 10% ratio EO-PEG nanoparticles showed an average diameter<235 nm (PDI<0.280) and a loading efficacy>75%; after 6 month of storage their size did not change significantly and the amount of the EOs decreased 25%, approximately. Furthermore, during this period, no chemical derivates were observed. The EOs nanoparticles produced a notable increase of the residual contact toxicity apparently due to the slow and persistent release of the active terpenes. In addition, the nanoformulation enhanced the EO contact toxicity and altered the nutritional physiology of both stored product pest. The results indicated that these novel systems could be used in integrated pest management program for T. castaneum and R. dominica control.

Lethal and sublethal effects of four essential oils on the egg parasitoids Trissolcus basalis.

The essential oils from leaves of Schinus molle var. areira, Aloysia citriodora, Origanum vulgare and Thymus vulgaris have showed potential as phytoinsecticides against the green stink bug, Nezara viridula. In this work were evaluated their toxicological and behavioral effects on the parasitoid Trissolcus basalis, a biological control agent of this pest insect. Essential oils were obtained via hydrodestillation from fresh leaves. Insecticide activity in T. basalis females was evaluated in direct contact and fumigation bioassays. Behavioral effects were evaluated in olfactometer bioassays. To evaluate the residual toxicity, females of the parasitoids were exposed to oil residues; in these insects, the sublethal effects were evaluated (potential parasitism and survivorship of immature stages). The essential oils from O. vulgare and T. vulgaris proved to be highly selective when used as fumigant and did not change parasitoid behavior. After one week, the residues of these oils were harmless and did not show sublethal effects against T. basalis. According with these results, essential oils have potential applications for the integrated management of N. viridula.