(2S,8Z)-2-Butyroxy-8-heptadecene: Major Component of the Sex Pheromone of Chrysanthemum Gall Midge, Rhopalomyia longicauda

Abstract

The sex pheromone of the chrysanthemum gall midge, Rhopalomyia longicauda (Diptera: Cecidomyiidae), the most important insect pest in commercial plantations of chrysanthemum, Dendranthema morifolium (Ramat.) Tzvel., in China, was identified, synthesized, and field-tested. Volatile chemicals from virgin females and males were collected on Porapak in China and sent to the United Kingdom for analysis. Coupled gas chromatographic-electroantennographic detection (GC-EAG) analysis of volatile collections from females revealed two compounds that elicited responses from antennae of males. These compounds were not present in collections from males. The major EAG-active compound was identified as 2-butyroxy-8-heptadecene by gas chromatographic (GC) retention indices, mass spectra, in both electron impact and chemical ionization modes, hydrogenation, epoxidation, and derivatization with dimethyldisulfide. The lesser EAG-active compound was identified as the corresponding alcohol. The ratio of butyrate to alcohol in the collections was 1:0.26. Racemic (Z)-8-heptadecen-2-ol and the corresponding butyrate ester were synthesized from (Z)-7-hexadecenyl acetate, and the synthetic compounds found to have identical GC retention indices and mass spectra to those of the natural, female-specific components. Analysis of the volatile collections on an enantioselective cyclodextrin GC column showed the natural pheromone contained (2S,8Z)-2-butyroxy-8-heptadecene. Field tests showed that rubber septa containing racemic (Z)-2-butyroxy-8-heptadecene were attractive to R. longicauda males. The (naturally occurring) S-enantiomer was equally as attractive as the racemate, while the R-enantiomer was not attractive to males, and did not inhibit the activity of the S-enantiomer. The attractiveness of the butyrate was significantly reduced by the presence of even small amounts of the corresponding alcohol.

Identification of 1-methyloctyl butanoate as the major sex pheromone component from females of the saddle gall midge, Haplodiplosis marginata (Diptera: Cecidomyiidae)

“…While most of these identified esters are acetoxy or diacetoxy compounds, H marginata produces butyroxy compounds. However, some other midges, such as the Chinese chrysanthemum midge, Rhopalomyia longicauda (Liu et al 2009), and the orange wheat blossom midge, Sitodiplosis mosellana (Gries et al 2000), are also known to produce butyroxy or dibutyroxy pheromone compounds.…”

The Chemical Ecology of Cecidomyiid Midges (Diptera: Cecidomyiidae)

“…In the structures reported, the functionality is most commonly an acetoxy-, butyroxy-, or keto-group, although two alcohols have been reported: (2S,10E)-10-tridecen-2-ol is an essential component of the pheromone of M. destructor (Andersson et al, 2009a), and (2S,8Z)-8-heptadecen-2-ol was detected in volatiles released by females of the Chinese chrysanthemum midge, Rhopalomyia longicauda. It is possible that the latter is a precursor to, or artifact from, the major component, (2S,8Z)-2-butyroxy-8-heptadecene, as addition of the alcohol to the butyrate in a range of relative amounts reduced the attractiveness of the latter to male midges (Liu et al, 2009).…”

“…In the pear midge, C. pyrivora, the presence of an acetoxyketone, as well as the more abundant diacetate, was detected in volatiles collected from virgin females (Table 1, entry 7), but addition of the former to the latter did not affect attractiveness (Amarawardana, 2009). In R. longicauda, the corresponding alcohol was detected, as well as the major mono-butyrate component (Table 1, entry 3), but addition of the alcohol to the butyrate over a range of ratios only reduced catches of males (Liu et al, 2009).…”

Identification of Female-produced Sex Pheromone of the Honey Locust Gall Midge, Dasineura gleditchiae

“…The Z-8 double bond seems to be particularly common, also occurring in pheromone components of the apple leaf curling midge, Dasineura mali, (Cross and Hall 2005;Suckling et al 2007), the Chinese chrysanthemum gall midge, Rhopalomyia spp. (Liu et al 2007), the pear leaf curling midge, D. pyri (Amarawardana et al 2006), and the blackcurrant leaf midge, D. tetensi (unpublished). It is of interest to note that D. gleditchiae produces the (R)-enantiomer, whereas the (S)-enantiomer has so far been found more commonly in other midge species, and even in a moth species, Kermania pistaciella Ams.…”