Avaliação do efeito letal da nanoemulsão de Rosmarinus officinalis L. sobre Bactrocera carambolae Drew e Hancock (Diptera: Tephritidae)

Abstract

Essential oils are complex volatile mixtures of secondary metabolites and several of them are considered potential insecticidal agents, including for agricultural pest control. On this context, nanoemulsions are considered promising delivery systems for novel aqueous pesticide products. Bactrocera carambolae Drew and Hancock is a quarentenary pest restrict that is found in the of Amapá and Roraima States (Brazil) and its dissenation through this country would lead to irreparable damage to brazilian fruticulture. Rosmarinus officinalis L., popularly known as rosemary, is an essential oil-rich plant and recognized as a promising insecticidal agent. The present study aims to evaluate insecticidal activity of the nanoemulsion prepared with R. officinalis essential oil against adults of Bactrocera carambolae. It was performed topical and contact bioassays. The nanoemulsions were prepared by low energy method at 50000 and 100000 ppm (expressed as essential oil content) and presented a fine transparent homogeneous appearance. Droplet size measured by dynamic light scattering was around 10 nm. Higher percentage of mortality (37.78 %) observed after 120 h of treatment on topical assay was induced by nanoemulsion with higher essential oil content (200 μg per insect). Significant difference between the nanoemulsion with higher content of essential oil was observed, when compared to control group and nanoemulsion with lower content of essential oil (F = 9.8773, P = 0.0003, df = 2.42). No statistical significant difference on mortality was observed by comparison of male with female. Contact bioassay of this nanoemulsion induced higher mortality (57.78 %) after 120 h, presenting statistical significant difference (F = 39.3611, P < 0.0001, df = 1.28) when compared to control group, which induced 12.22% of mortality. Statistical significant difference was observed on percentage of mortality on male (77.78%), when compared to female (37.78%) (F = 12.4090, P = 0.004, df = 1.28). Thus, ours results shows the first time the insecticidal activity a nanostructured system containing essential oil from R. officinalis, showing the potential of this novel nanoproduct on integrated practices of B. carambolae control