RESUMO
Plutella xylostella (L.) is responsible for considerable vegetable crop losses in the metropolitan region of Manaus, Brazil. In recent decades, essential oils have been investigated as an alternative to synthetic insecticides. The genusPiperis widely distributed in Amazonia and essential oils from these plants have insecticidal properties. This study describes the chemical composition of the essential oils fromPiper capiterianumandPiper krukoffiias well as the lethal and sublethal effects onP. xylostella. The phytotoxicity of the oils on the host plant was also evaluated. Globulol was the major constituent of theP. krukoffiioil ando-cymene was the major constituent of theP. capitarianumoil. The oil fromP. capiterianumexhibited greater toxicity to larvae and eggs. This oil also presented greater repellant action, feeding deterrence and mild phytotoxicity to the host plant (Brassicae oleraceae). The findings suggest that this oil can be used in the preparation of a formulated insecticide for the management ofP. xylostellain different development phases. However, further studies are needed to evaluate the effect of this oil on crops under field conditions as well as non-target organisms and determine the cost-benefit ratio of a product formulated withP. capitarianumoil.
Assuntos
Inseticidas , Óleos Voláteis , Animais , Brasil , Inseticidas/química , Inseticidas/toxicidade , Larva , Óleos Voláteis/química , Óleos Voláteis/toxicidade , Óleos de Plantas/toxicidadeRESUMO
The aim of this study was to investigate the chemical composition and acaricidal effect of two Psidium species essential oils and selected compounds on Tetranychus urticae. Essential oils from the leaves of Psidium laruotteanum and Psidium myrsinites were obtained through hydrodistillation, analyzed using CG-FID and CG-MS and evaluated for toxicity to T. urticae by fumigation and residual contact. The susceptibility of T. urticae to monoterpenes and sesquiterpenes was also investigated. The major constituents of the P. laruotteanum oil were (E)-nerolidol (9.6 ± 0.4%) and γ-terpinene (9.4 ± 0.6%) and the major constituents of the P. myrsinites oil were ß-caryophyllene (21.2 ± 0.9%) and α-humulene (10.3 ± 0.5%). Based on the LC50 estimates, no significant differences were found between the two oils regarding toxicity by fumigation or residual contact. ß-Caryophyllene and (E)-nerolidol had the highest level of toxicity, independently of the method investigated. The findings indicate that both oils and selected constituents, especially ß-caryophyllene and (E)-nerolidol, are promising as natural acaricidal agents that affect T. urticae through more than one mode of action.
Los aceites esenciales de las hojas de Psidium laruotteanum y Psidium myrsinites se obtuvieron por hidrodestilación, se analizaron por CG-FID y CG-MS, y se evaluaron sus toxicidades por fumigación y contacto residual contra Tetranychus urticae. Se investigó también la susceptibilidad del T. urticae a monoterpenos y sesquiterpenos. En el aceite esencial de P. laruotteanum, (E)-nerolidol (9.6 ± 0.4%) y γ-terpinene (9.4 ± 0.6%) se identificaron como constituyentes mayoritarios, mientras que en el aceite esencial de P. myrsinites, ß-caryophyllene (21.2 ± 0.9%) y α-humulene (10.3 ± 0.5%) se encontraron como mayoritarios. Con base en las CL50 estimadas, no se observaron diferencias significativas entre las toxicidades de los aceites por fumigación, y tampoco por contacto residual. ßCaryophyllene y (E)-nerolidol presentaron las mayores toxicidades, independientemente del método investigado. Estos resultados indican, que los dos aceites, así como los constituyentes seleccionados, entre los que se destacan ß-caryophyllene y (E)-nerolidol, son promisores agentes acaricidas naturales por actuar en el T. urticae por más de un mecanismo de acción.
