Virus infection frequently modifies plant phenotypes, leading to changes in behaviour and performance of their insect vectors in a way that transmission is enhanced, although this may not always be the case. Here, we investigated Bemisia tabaci response to tomato plants infected by Tomato chlorosis virus (ToCV), a non-circulative-transmitted crinivirus, and Tomato severe rugose virus (ToSRV), a circulative-transmitted begomovirus. Moreover, we examined the role of visual and olfactory cues in host plant selection by both viruliferous and non-viruliferous B. tabaci. Visual cues alone were assessed as targets for whitefly landing by placing leaves underneath a Plexiglas plate. A dual-choice arena was used to assess whitefly response to virus-infected and mock-inoculated tomato leaves under light and dark conditions. Thereafter, we tested the whitefly response to volatiles using an active air-flow Y-tube olfactometer, and chemically characterized the blends using gas chromatography coupled to mass spectrometry. Visual stimuli tests showed that whiteflies, irrespective of their infectious status, always preferred to land on virus-infected rather than on mock-inoculated leaves. Furthermore, whiteflies had no preference for either virus-infected or mock-inoculated leaves under dark conditions, but preferred virus-infected leaves in the presence of light. ToSRV-infection promoted a sharp decline in the concentration of some tomato volatiles, while an increase in the emission of some terpenes after ToCV infection was found. ToSRV-viruliferous whiteflies preferred volatiles emitted from mock-inoculated plants, a conducive behaviour to enhance virus spread, while volatiles from ToCV-infected plants were avoided by non-viruliferous whiteflies, a behaviour that is likely detrimental to the secondary spread of the virus. In conclusion, the circulative persistent begomovirus, ToSRV, seems to have evolved together with its vector B. tabaci to optimise its own spread. However, this type of virus-induced manipulation of vector behaviour was not observed for the semi persistent crinivirus, ToCV, which is not specifically transmitted by B. tabaci and has a much less intimate virus-vector relationship.

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.

This work describes the structural elucidation of the sex pheromone of the soybean stink bug, Pallantia macunaima. The biological activity of the synthetic pheromone was demonstrated by behavioral and EAD experiments. Furthermore, the absolute configuration of the natural pheromone was determined as (6R,10S)-6,10,13-trimethyltetradecan-2-one. This is the first ketone identified as a male-produced sex pheromone in Pentatomidae, and the trivial name, pallantione, was assigned to this novel pheromone molecule.

Agroecus griseus is a serious corn pest in Brazil. Contents of the dorsal abdominal glands (DAGs) in nymphs, and the metathoracic gland (MTG) in adults of this species were characterized and quantified. Compounds found were similar to those of other Pentatomidae species and included aliphatic hydrocarbons, aldehydes, oxo-alkenals, and esters. However, two compounds were found in the MTG that have not been described previously for this family. Mass spectrometry, infrared spectroscopy, and gas chromatographic analysis using coinjection with authentic standards confirmed the identities of the compounds as enantiopure (S)-2-methylbutyl acetate and 3-methyl-2-butenyl acetate. The five nymphal instars showed significantly different ratios of components, mainly between those of the first and later instars. No significant differences were detected in MTG contents between sexes. Gas chromatography (GC) analysis of aeration extracts of males and females showed the presence of a compound released exclusively by males. Gas chromatography - electroantennographic detection (GC-EAD) assays indicated that the male-specific compound is bioactive in females, suggesting the presence of an attractant pheromone. The mass spectrum and infrared data for this compound matched with methyl 2,6,10-trimethyltridecanoate, a sex pheromone component previously detected in the stink bugs, Euschistus heros and E. obscurus. The synthetic standard coeluted with the natural pheromone on two different GC stationary phases, confirming the proposed structure. Y-tube olfactometer assays showed that the synthetic standard was strongly attractive to females, and GC-EAD tests produced responses with antennae from females similar to those of the natural pheromone.

No abstract

Edessa meditabunda is a secondary pest within the piercing-sucking stink bug complex that attacks soybean crops in Brazil. The behavioral responses of males and females to aeration extracts from conspecifics suggested the presence of a male-produced sex pheromone. Gas chromatographic (GC) analysis of male and female aeration extracts revealed the presence of two male-specific compounds in a ratio of 92:8. Gas chromatographic -electroantennographic detection (GC-EAD) assays indicated that the major component is bioactive for females, supporting the behavioral data. Analysis of the mass and infrared spectra of the male-specific compounds suggested that they were both methyl-branched long-chain methyl esters. On the basis of the mass spectra of the respective hydrocarbons obtained by micro derivatizations, the structures of these methyl esters were proposed to be methyl 4,8,12-trimethylpentadecanoate (major) and methyl 4,8,12-trimethyltetradecanoate (minor). An 11 step synthetic route that was based on a sequence of Grignard reactions, starting from cyclopropyl methyl ketone, was developed to obtain synthetic standards with a 7.9 % overall yield for the major compound and a 9.9 % yield for the minor. The synthetic standards co-eluted with the natural pheromones on three different GC stationary phases. Y-tube olfactometer assays showed that the synthetic standards, including the major compound alone and a mixture of the major and minor compounds in the proportion found in natural extracts, were strongly attractive to females.

No abstract

O conteúdo das glândulas abdominais dorsais em ninfas e das glândulas metatorácicas em machos e fêmeas (10, 20 e 30 dias de idade adulta) foi caracterizado e quantificado para o percevejo Pallantia macunaima. O principal componente encontrado nas ninfas e adultos foi o tridecano, com menores quantidades de outros hidrocarbonetos alifáticos, aldeídos, oxo-alcenais e ésteres. Os cinco ínstares apresentaram diferenças significativas nas proporções dos compostos encontrados, principalmente entre aqueles do primeiro ínstar em relação aos demais ínstares. Nenhuma diferença significativa foi detectada na proporção dos compostos das glândulas metatorácicas entre os machos e fêmeas, porém, entre indivíduos de diferentes idades, (E)-2-hexenal e acetato de (E)-2-decenila diminuiram significativamente de 10 para 20 dias de idade.The contents of the dorsal abdominal glands in nymphs and the metathoracic glands in adult males and females (10, 20 and 30 days old) were characterized and quantified for the stink bug, Pallantia macunaima. The major component for nymphs and adults was tridecane, with lesser amounts of other aliphatic hydrocarbons, aldehydes, oxo-alkenals and esters. The five nymphal instars showed significant differences in the proportions of compounds present, mainly between those of the first instar compared to the dorsal abdominal glands components of later instars. No significant differences were detected in the proportion of metathoracic gland components between the sexes but, between individuals of different ages, (E)-2-hexenal and (E)-2-decenyl acetate significantly decreased in adults from 10 to 20 days of age.