Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2006
Publication Date: 11/7/2006
Citation: Bartelt, R.J., Hossain, M.S. 2006. Development of synthetic food-related attractant for Carpophilus davidsoni and its effectiveness in the stone fruit orchards in Southern Australia. Journal of Chemical Ecology. 32:2145-2162. Interpretive Summary: Nitidulid beetles (“sap” beetles) are currently the most serious pests of peaches and nectarines in southern Australia. For a number of regulatory and practical reasons, conventional insecticidal sprays are not used to protect the crops from these pests; and as an alternative, attractant-based killing stations have been developed. These protect the crop by greatly reducing local populations of the beetles before the fruit crops ripen and become susceptible to beetle damage. Originally, the killing stations were baited with beetle pheromone (developed at NCAUR), overripe peaches, and fermenting peach juice. The peaches in the stations were treated with a small amount of insecticide, allowing beetle control to be achieved without having to spray the crop on the trees directly. The stations were effective, but using fruit and fermenting juice was unwieldy and inconvenient for the growers; and a synthetic replacement was required. The present research describes the development of a synthetic version of the fruit-related attractants, using a set of complementary techniques for chemical analyses and laboratory evaluation of beetle attraction. A six-component blend of simple, readily available compounds was devised, modeled after fermenting peach juice. It was highly attractive in both laboratory and field tests, and research to use it in the killing stations has begun. The reported information will be of value to managers of these stone fruit pests, and the techniques will be of interest to chemical ecologists and other scientists investigating chemical attractants.
Technical Abstract: A highly attractive synthetic blend of host-related volatile compounds was developed for the nitidulid beetle, Carpophilus davidsoni, as part of a program for managing this pest in Australian peach orchards. Fermenting peach juice and whole peaches and nectarines served as chemical models for the attractant; and synthetic formulations were sought that matched the natural sources, both with respect to emission rates of key chemicals (in ng/min) and attractiveness to flying beetles. All volatile sources were kept in airstreams during laboratory chemical measurements. These airstreams were subsequently directed to the wind-tunnel behavioral assay, allowing the determined emission rates of compounds to be associated with particular levels of attractiveness. Chemical sampling of airstreams was by solid-phase microextraction, and analysis was by gas chromatography and mass spectrometry. A volatile-delivery system was coupled to the wind tunnel and allowed facile manipulation of natural and synthetic scents. The final blend, modeled after fermenting peach juice, contained ethanol as the main constituent and 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, acetaldehyde, and ethyl acetate as minor constituents, all in water solution. Blend components were synergistic, and use of a mixture is essential for optimal attractiveness. The synthetic blend was highly effective in the field and is intended to replace fermenting peach juice and overripe peaches, which were previously used as synergists of the Carpophilus spp. aggregation pheromones in attract-and-kill stations.