Jorge Omar Werdin González

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.

Composition and biological activity of essential oils from Labiatae against Nezara viridula (Hemiptera: Pentatomidae) soybean pest

BACKGROUND Plant essential oils have been recognised as an important natural source of insecticide. This study analysed the chemical constituents and bioactivity of essential oils that were isolated via hydrodistillation from Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) against eggs, second instar and adults of Nezara viridula (L.). RESULTS The major component of oregano was p-cymene, and, for thyme, thymol. The ovicidal activity was tested by topical application; the essential oil from thyme was more effective. The fumigant activity was evaluated in an enclosed chamber; the LC50 values for oregano were 26.8 and 285.6 µg mL(-1) for nymphs and adults respectively; for thyme they were 8.9 µg mL(-1) for nymphs and 219.2 µg mL(-1) for adults. To evaluate contact activity, a glass vial bioassay was used; the LC50 values for oregano were 1.7 and 169.2 µg cm(-2) for nymphs and adults respectively; for thyme they were 3.5 and 48.8 µg cm(-2) respectively. The LT50 analyses for contact and fumigant bioassays indicated that thyme was more toxic for nymphs and adults than oregano. Both oils produced repellency on nymphs and adults. CONCLUSION These results showed that the essential oils from O. vulgare and T. vulgaris could be applicable to the management of N. viridula.

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.

Evaluation of sublethal effects of polymer-based essential oils nanoformulation on the german cockroach

The German cockroach, Blattella germanica (L.), is a serious household and public health pest worldwide. The aim of the present study was to evaluate the sublethal activity of polymer-based essential oils (EOs) nanoparticles (NPs) on adults of B. germanica. The LC50 and LC25 for contact toxicity were determined. To evaluate the repellency of EOs and NPs at LC25, a software was specially created in order to track multiple insects on just-recorded videos, and generate statistics using the obtained information. The effects of EOs and NPs at LC25 and LC50 on the nutritional physiology were also evaluated. The results showed that NPs exerted sublethal effects on the German cockroach, since these products enhance the repellent effects of the EOs and negatively affected the nutritional indices and the feeding deterrence index.

Composition, Repellent, and Insecticidal Activities of Two South American Plants against the Stored Grain Pests Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae)

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 Te 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 (LC50 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 (LD50 = 7.35 μg/insect) than the EO of A. citriodora (LD50 = 13.8 μg/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.

TABLA DE VIDA Y FECUNDIDAD DE NEZARA VIRIDULA VAR. SMARAGDULA (HEMIPTERA: PENTATOMIDAE) ALIMENTADA SOBRE FRUTOS DE PHASEOLUS VULGARIS L. (FABACEAE)

El objetivo del presente estudio es determinar la duracion del ciclo de vida, proporcion sexual, longevidad, fecundidad y tabla de vida horizontal por edades de Nezara viridula var. smaragdula, insecto plaga de la soja alimentado sobre frutos de Phaseolus vulgaris. Para ello se establecio una colonia en laboratorio bajo las siguientes condiciones: temperatura 28 ± 1°C; 60/70% HR y fotoperiodo 14 L - 10 O. Se estudio el ciclo vital y tabla de vida a partir de una cohorte de 4.008 huevos. Los resultados obtenidos fueron: tiempo de desarrollo de los estados inmaduros: huevos-ninfas 49 ± 4 dia; longevidad de adultos: 41 ± 9 dias; proporcion sexual (♀/♂): 1,24. La tasa de mortalidad especifica de cada estadio (qx) fue: huevo: 0,086; ninfa I: 0,173; ninfa II: 0,366; ninfa III: 0,540; ninfa IV: 0,426; ninfa V: 0,601; la fecundidad (mx): 112 huevos/hembra y el indice reproductor neto (R0): 5,6. Estos parametros resultan de interes no solo para conocer la dinamica poblacional en laboratorio sino para disenar estrategias de control de esta plaga