Aqueous extracts of nine plants, known to have medicinal activity, were tested for their toxicity against the sweet potato whitefly, Bemisia tabaci Genn. (Homoptera: Aleurodidae) compared to the toxicity of the insecticide, Imidacloprid. Extracts of Lepidiuim sativum L. (Brassicales: Brassicaceae) killed 71 % of early stage nymphs, which was not significantly different from mortality caused by Imidacloprid. Treatment of pupae with three plant extracts, L. sativum, Achillea biebersteinii L. (Asterales: Asteraceae), or Retama raetam (Forssk.) Webb and Berthel (Fabales: Fabaceae) prevented adult development, and treatment with R. raetam extract killed adults, at levels that were not significantly different from Imidacloprid. None of the other plants showed significant toxicity. However extracts of four plants, Pimpinella anisum L. (Apiales: Apiaceae), Galium longifolium (Sibth. and SM.) (Gentianales: Rubiaceae), R. raetam and Ballota undulata Bentham (Lamiales: Lamiaceae) had a repellent effect.

Successful clonal propagation of Stevia rebaudiana was achieved using microshoots as a primary step for in vitro conservation. Maximum proliferation was obtained on Murashige and Skoog (MS) medium supplemented with 1.5 mg L -1 benzyl amino purine and 0.2 mg L -1 indole-3-butyric-acid (IBA). Auxin increased rooting percentage of shoots at concentration of 0.4 mg L -1 IBA, indole-3-acetic-acid or naphthalene acetic acid and no rooting occurred without plant growth regulator. A survival of 90% was achieved when rooted explants were acclimatized in vivo in 1 soil: 1 perlite: 1 peat. In vitro S. rebaudiana shoots were successfully stored for up to 32 weeks on MS medium supplemented with an appropriate concentration of sucrose, sorbitol or mannitol, at 24 ± 2°C. After 32 weeks, 93.6% of the shoots were able to survive. Moreover, 89.3% of them were able to regrow when stored under light conditions. Cryopreservation by vitrif ication was successfully achieved (65.6% regrowth) when shoot tips were precultured on a medium supplemented with 0.4 M sorbitol for 2 d, followed by loading shoot tips with 80% concentrated plant vitrification solution 2 (PVS2) for 20 min; then dehydrated with 100% PVS2 for 60 min at 0°C prior to storage in liquid nitrogen. This procedure is easy to handle and produced a high levels of shoot formation. This protocol could be useful for longterm storage of S. rebaudiana germplasm.Additional key words: cryopreservation; in vitro conservation; micropropagation; osmoticum; root formation. Resumen Propagación clonal y almacenamiento criogénico de la planta medicinal Stevia rebaudianaSe logró con éxito la propagación clonal de Stevia rebaudiana, utilizando microtallos como primer paso para su conservación in vitro. Se obtuvo la proliferación máxima en el medio Murashige y Skoog (MS) suplementado con 1,5 mg L -1 de bencil amino purina y 0,2 mg L -1 de ácido indol-3-butírico (IBA). Las auxinas aumentaron el porcentaje de enraizamiento de los brotes en la concentración de 0,4 mg L -1 de IBA, ácido indol-3-acético o el ácido naftalen acético, pero no se produjo enraizamiento sin regulador del crecimiento vegetal. Se logró una supervivencia del 90% cuando los explantes enraizados fueron aclimatizados in vivo en 1 suelo: 1 perlita: 1 turba. Se almacenaron con éxito brotes de S. rebaudiana in vitro hasta 32 semanas a 24 ± 2°C, en medio MS suplementado con una concentración apropiada de sacarosa, sorbitol o manitol. Después de 32 semanas, el 93,6% de los brotes fueron capaces de sobrevivir y el 89,3% fueron capaces de rebrotar cuando se almacenaron bajo condiciones de luz. Se logró con éxito (65,6% rebrotes) la criopreservación por vitrificación cuando los ápices se pre-cultivaron durante 2 días en un medio suplementado con sorbitol 0,4 M, y a continuación con una solución de vitrificación de la planta 2 (PVS2) al 80% durante 20 minutos, seguido de una deshidratación con PVS2 al 100% durante 60 min a 0°C antes de su almacenamiento en nitrógeno líquido. Este procedimiento es fácil de ejecutar y puede ser...

The ability of bumble bees to disseminate conidia of Beauveria bassiana (Balsamo) Vuillemin from hive-mounted dispensers to greenhouse sweet peppers for the control of tarnished plant bug (TPB) and western Xower thrips (WFT) was investigated in greenhouse trials using large screened enclosures. Samples collected from the enclosures (four treatments) on two sampling dates showed that 97, 90, 91, and 42% of the collected bees, Xowers, leaves, and TPB, respectively, showed detectable densities of B. bassiana on the Wrst sampling date. On the second sampling date, 99, 96, 87, and 30% of collected bees, Xowers, leaves, and TPB, respectively, showed detectable densities of the fungus. Mean mortalities of TPB collected from cages treated with B. bassiana were 34 and 45% compared to 9 and 15% in the controls on the Wrst and second sampling dates, respectively. Mean infection rates of WFT were 40 and 34% compared to 3% in the controls on the Wrst and second sampling dates, respectively. These results indicate that bumble bees are an eVective means of vectoring the fungal conidia to the crop. The pollinator vector technology is a novel example of integrating agro-ecosystem processes of pollination and pest management, that reduces the reliance on insecticides and increases crop yields and quality.

Toxicity and repellent activities of aqueous extracts of nine medicinal plants were evaluated on diVerent life stages of the sweet potato whiteXy, Bemisia tabaci. Tomato plants infested with whiteXies were dipped in 10% (wt/wt) of each plant extract for toxicity evaluation. Repellency was evaluated in a choice experiment with detached tomato leaves. All extracts evaluated were relatively ineVective against the adult stage. Extracts of Ruta chalepensis, Peganum harmala and Alkanna strigosa were eVective in reducing the numbers of B. tabaci immatures similar to the reduction observed in the imidacloprid treatment. These three extracts were not detrimental B. tabaci parasitoid, Eretmocerus mundus. In addition, the plant extracts Urtica pilulifera and T. capita were repellent to B. tabaci adults. These results indicate that the extracts from the plants R. chalepensis, P. harmala and A. strigosa could act as a potential source for natural product developed for B. tabaci management.

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