Insecticidal effects of plant extracts on immature whitefly bemisia tabaci genn. (hemiptera: Aleyroideae)

Abstract

Background: The whitefly (Bemisia tabaci Genn.) is a widely distributed and highly harmful plant pest species. The management of B. tabaci has been typically carried out by chemical pesticides. In the last decade however, there has been an increasing interest in natural products, particularly those of plant origin, to control this pest species. In the present work, aqueous and ethanolic extracts of native plants from the flora of the Yucatán peninsula (Acalypha gaumeri, Annona squamosa, Carlowrightia myriantha, Petiveria alliaceae and Trichilia arborea) and the introduced plant Azadirachta indica were collected and evaluated for insecticidal activity against eggs and nymphs Bemisia tabaci. Results: Most of the aqueous and ethanolic extracts showed high insecticidal effects on B. tabaci eggs. The lowest LC50 values were recorded in the aqueous extracts of A. gaumeri (0.39% w/v), A. squamosa (0.36% w/v), P. alliaceae (0.42% w/v) and A. indica (0.30% /v), as well as in the ethanolic extracts of P. alliaceae (2.09 mg mL-1) and T. arborea (2.14 mg mL-1). On the other hand, B. tabaci nymphs were not affected by the aqueous extracts, but were highly sensitive to the ethanolic extracts of the tested plants. The lowest LC50 values were recorded in the ethanolic extracts of P. alliaceae (1.27 mg ml-1) and T. arborea (1.61 mg mL-1). The GC-MS analysis showed that phytol was the major component of the ethanolic extract of P. alliaceae and fatty acids were the major components of ethanolic extract of T. arborea. Conclusions: Overall, results suggest that ethanolic extracts of P. alliaceae and T. arborea leaves showed the highest insecticidal effects on eggs and nymphs B. tabaci. The extracts from P. alliaceae and T. arborea are good candidates to be developed as sources of natural insecticides for the management of immature B. tabaci since their effects were comparable with that showed by the extracts of A. indica, a well-known plant species for its insecticidal activity. © 2013 by Pontificia Universidad Católica de Valparaíso, Chile.