Abstract
The beetle Homalinotus depressus (Coleoptera: Curculionidae) is a major pest of coconuts in the Northern region of Brazil, for which environmentally friendly methods of control are desired. Behavioral responses of H. depressus to airborne volatile extracts from conspecifics suggested the presence of a male-produced aggregation pheromone. GC analyses of these extracts showed the presence of four male-specific compounds. Analytical data in combination with the synthesis of standards led to the identification of the male-released semiochemicals as epoxyisophorone (1), isophorone (2), homalinol (3), and 2-hydroxyisophorone (4), of which (3) was the major constituent. The configuration of homalinol was determined to be cis on the basis of retention times of synthetic cis and trans synthetic standards. Enantiomers of cis-homalinol were obtained in high enantiomeric excess by using biocatalysis. Their separation on a GC enantioselective column (β-Dex325®), allowed us to unambiguously determine that the absolute configuration of natural homalinol was (1R,2R,6S). Field bioassays demonstrated that both the synthetic major compound per se and mixtures of all four male-specific compounds were attractive to H. depressus.
Highlights
The beetle Homalinotus depressus (Coleoptera: Curculionidae) is a major pest of coconuts in the Northern region of Brazil, for which environmentally friendly methods of control are desired
The chemical structures of the compounds described as aggregation pheromones of Curculionidae to date can be divided into two different classes
Volatile compounds emitted by H. depressus were collected by aeration and the GC comparison of aeration extracts from males to similar extracts from females showed the presence of four male-specific compounds (Fig. 1)
Summary
Interrupting the sap flow and promoting failing of flowers and fruits. In 2008, H. depressus was reported for the first time as a coconut pest in the Brazilian northern region[18]. Due to the lack of lures for trapping adult beetles, population densities are estimated by manual collections of beetles in the field. Semiochemicals, such as sex and/or aggregation pheromones, are highly desirable for trapping and possibly use in direct control strategies We describe the isolation, identification, and field evaluation of an aggregation pheromone produced by H. depressus
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