Effects of the essential oil obtained from Pilocarpus spicatus Saint-Hilaire (Rutaceae) on the development of Rhodnius prolixus nymphae

Abstract

RESUMO: "Efeitos do óleo essencial de Pilocarpus spicatus Saint-Hilaire (Rutaceae) no desenvolvimento de ninfas de Rhodnius prolixus". Bioensaios contra ninfas de 5º estádio de Rhodnius prolixus foram conduzidos utilizando-se óleo essencial de Pilocarpus spicatus extraído por hidrodestilação. Os principais resultados podem ser resumidos como se segue: (i) altos níveis de toxicidade e paralisia associados à discreta inibição da muda foram induzidos pela aplicação tópica de 0,5 μL ou 1,0 μL do óleo essencial por inseto; (ii) fagoinibição parcial, altos níveis de inibição da muda, período intermuda prolongado e alto número de insetos paralisados mas ausência de toxicidade foram observados após tratamento oral com 5,0 μL ou 10 μL de óleo essencial de P. spicatus por mL de sangue ingerido. A importância destes resultados em relação a eventos biológicos relevantes em R. prolixus é aqui discutida. Unitermos: Rhodnius prolixus, Pilocarpus spicatus, óleo essencial.ABSTRACT: Bioassays against fi fth-instar nymphae of Rhodnius prolixus were conducted with essential oil of Pilocarpus spicatus extracted by hydrodistillation. The main results may be summarized as follows: (i) high levels of toxicity and paralysis together with discrete moulting inhibition were caused by topical application of either 0.5 μL or 1.0 μL per insect of the crude essential oil; (ii) partial fagoinhibition, high moulting inhibition, prolonged intermoulting period and high number of paralyzed insects, but no toxicity were observed after oral treatment using either 5 μL or 10 μL of Pilocarpus spilcatus essential oil per mL of ingested blood meal. The importance of these results in relation to the relevant biological events in R. prolixus is herein discussed.

Extrato metanólico de farinha de folhas de mandioca como alternativa ao controle da lagarta-do-cartucho e de formigas cortadeiras

“…Entretanto, para ambos os tratamentos, não foram observadas relações entre as doses utilizadas e a mortalidade acumulada, já que todos os tratamentos foram agrupados em um único grupo na distribuição de Weibull. Em estudo utilizando óleo essencial de Pilocarpus spicatus Saint-Hilaire (Rutaceae) para o controle de ninfas de quinto instar de Rhodnius prolixus Stål (Hemiptera: Reduviidae), de maneira semelhante ao constatado no presente trabalho, os autores não puderam propor uma relação entre a dose aplicada e seu efeito na mortalidade (MELLO et al, 2007).…”

Lethal and sublethal effects of essential oil of Lippia sidoides (Verbenaceae) and monoterpenes on Chagas’ disease vector Rhodnius prolixus

“…However, few studies report the fagoinhibition effects of essential oils and terpenes against triatomines. Mello et al (2007) observed that the orally treatment of R. prolixus nymphs with the essential oil of Pilocarpus spicatus (Rutaceae) decreased significantly the blood intake in comparison to the control group. Some antifeedant compounds interfere with the perception of feeding stimulants preventing the insects from obtaining the correct taste information, affecting the insect feeding behavior (Garcia et al 1991).…”

Laboratory evaluation of the effects of Manilkara subsericea (Mart.) Dubard extracts and triterpenes on the development of Dysdercus peruvianus and Oncopeltus fasciatus

“…Overaged immature insects with greatly extended instar stages may survive for several weeks but are unable to undertake metamorphosis, adult physiology or reproduction. The resulting body deformities with the above treatments have been a common finding in hemimetabolous insects treated with compounds that interfere with moult processes, acting either by a neuroendocrine route, which inhibits the synthesis of ecdysone,, or directly disrupting the cuticle deposition by the blockage of chitin synthesis , …”

“…Secondary plant metabolites, including growth regulators, are important molecules that became involved in coevolutionary mechanisms by interacting with other organisms, mainly insects . Some of these secondary metabolites are highly toxic to insects and directly disrupt specific physiological routes related to neuroendocrine and feeding systems, metamorphosis (inducing moulting disorders and morphogenetic defects), reproduction, diapause and behaviour of arthropods, constituting vulnerable points for the control of pest populations based on knowledge of the life cycles of insects …”