RESUMO
The bearded weevil, Rhinostomus barbirostris (Coleoptera: Curculionidae: Dryophthorinae), attacks coconut trees, oil palms and other species of Arecaceae. Besides direct damage, R. barbirostris may be a vector of diseases in coconut and oil palms, such as stem bleeding (resinosis) and red ring disease. Currently, the only method to control this weevil is by visual observation of damage and removal of infected plants. Semiochemical-based trapping could improve the effectiveness of monitoring and management of R. barbirostris. In comparisons of volatiles released by R. barbirostris males and females by gas chromatography (GC) two male-specific compounds were observed. GC-mass spectrometry (MS) and GC-Fourier transform-infrared (FTIR) analyses of the natural compounds suggested these were diastereoisomers of 5-hydroxy-4-methylheptan-3-one, also known as sitophilure, a pheromone component of other dryophthorine species. Synthesis of the mixture of all four stereoisomers of sitophilure was performed in two steps, and the chemical structures were confirmed by comparing GC retention times and MS and FTIR spectra of natural and synthetic compounds. The absolute configurations of the two male-specific compounds were elucidated by enantioselective GC; the major component was the (4S,5R)-isomer, and the minor component (4S,5S)-sitophilure. In analyses by GC-electroantennography (EAG) the antennae of male and female R. barbirostris only responded to the (4S,5R)-isomer of the synthetic sitophilure. The stereoisomeric mixture of sitophilure was attractive to both sexes of R. barbirostris in laboratory experiments in the presence of sugar cane volatiles, and a similar result was obtained in a preliminary field trapping test.
Assuntos
Atrativos Sexuais/análise , Atrativos Sexuais/metabolismo , Gorgulhos/fisiologia , Animais , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Masculino , Conformação Molecular , Atrativos Sexuais/síntese química , Comportamento Sexual Animal , Gorgulhos/químicaRESUMO
Foi avaliada a ocorrência do parasitóide Billaea rhynchophorae (Blanchard) em larvas de Rhynchophorus palmarum (L.) em plantações das palmeiras piaçava (Attalea funifera Mart.) e dendê (Elaeis guineensis Jacquin) no Sudeste da Bahia. As porcentagens mensais de parasitismo foram determinadas durante 13 meses, entre novembro de 2000 e novembro de 2001, comparando-se o número de casulos de R. palmarum parasitados e não-parasitados. O índice médio de parasitismo foi 40%, variando de 57% em novembro de 2000 a 18% em julho de 2001. Enquanto não existe método de criação massal do parasitóide, recomenda-se uma prática simples de manejo que visa a preservar seu efeito benéfico nas plantações de palmeiras.
Assuntos
Animais , Dípteros/fisiologia , Controle Biológico de Vetores/métodos , Doenças das Plantas/parasitologia , Gorgulhos/parasitologiaRESUMO
The occurrence of the tachinid parasitoid Billaea rhynchophorae (Blanchard) on larvae of the palm weevil Rhynchophorus palmarum (L.) was evaluated in plantations of piassava palm (Attalea funifera Mart.) and African oil palm (Elaeis guineensis Jacquin), in southeastern Bahia, Brazil. The monthly percentages of parasitism were evaluated during 13 months, from November 2000 to November 2001, based on the comparison between the number of parasitized and non-parasitized cocoons of R. palmarum. Mean parasitism was 40% and ranged from 50% in November 2000 to 18% in July 2001. While there is no method of mass reproduction of the parasitoid, a simple management practice is recommended, in order to preserve its beneficial effects in palm plantations.