Field Attractants for Pachnoda interrupta Selected by Means of GC-EAD and Single Sensillum Screening

Abstract

The sorghum chafer, Pachnoda interrupta Olivier (Coleoptera: Scarabaeidae: Cetoniinae), is a key pest on sorghum, Sorghum bicolor (L.) Moench (Poaceae), in Ethiopia. At present there is a lack of efficient control methods. Trapping shows promise for reduction of the pest population, but would benefit from the development of attractive lures. To find attractants that could be used for control of P. interrupta, either by mass trapping or by monitoring as part of integrated pest management, we screened headspace collections of sorghum and the highly attractive weed Abutilon figarianum Webb (Malvaceae) for antennal activity using gas chromatograph-coupled electroantennographic detection (GC-EAD). Compounds active in GC-EAD were identified by combined gas chromatography and mass spectrometry (GC-MS). Field trapping suggested that attraction is governed by a few influential compounds, rather than specific odor blends. Synthetic sorghum and abutilon odor blends were attractive, but neither blend outperformed the previously tested attractants eugenol and methyl salicylate, of which the latter also was part of the abutilon blend. The strong influence of single compounds led us to search for novel attractive compounds, and to investigate the role of individual olfactory receptor neurons (ORNs) in the perception of kairomones. We screened the response characteristics of ORNs to 82 putative kairomones in single sensillum recordings (SSR), and found a number of key ligand candidates for specific classes of ORNs. Out of these key ligand candidates, six previously untested compounds were selected for field trapping trials: anethole, benzaldehyde, racemic 2,3-butanediol, isoamyl alcohol, methyl benzoate and methyl octanoate. The compounds were selected on the basis that they activated different classes of ORNs, thus allowing us to test potential kairomones that activate large non-overlapping populations of the peripheral olfactory system, while avoiding redundant multiple activations of the same ORN type. Field trapping results revealed that racemic 2,3-butanediol is a powerful novel attractant for P. interrupta.

Characterization of olfactory sensory neurons in the white clover seed weevil, Apion fulvipes (Coleoptera: Apionidae)

“…In contrast, the single sensillum recording (SSR) technique is less affected by the size or morphology of the antenna. SSR has previously been used to characterize responses of olfactory sensory neurons (OSNs) in several species of weevils (Bichão et al, 2003(Bichão et al, , 2005Blight et al, 1995;Wibe and Mustaparta, 1996), and has also proven useful when screening for compounds to be used in pest control (Bengtsson et al, 2009).…”

Peripheral modulation of pheromone response by inhibitory host compound in a beetle

“…Decisions regarding whether to progress towards an odor source, or to abort, are probably based upon a balance mechanism in which attractive and anti-attractive/repellent inputs in the combined 'odor bouquet' are weighed against each other. In the insect olfactory system, specific olfactory receptor neurons (ORNs) constitute separate input channels, each detecting compounds from different chemical and biological categories (Andersson et al, 2009;Bengtsson et al, 2009;Larsson et al, 2001;Mustaparta, 1975;Wibe and Mustaparta, 1996). ORN axons project to the glomeruli of the primary olfactory center, the antennal lobe, where integration of odor input takes place through lateral interactions between glomeruli (Olsen and Wilson, 2008;Shang et al, 2007;Silbering et al, 2008).…”

Pheromone-based Mating and Aggregation in the Sorghum Chafer, Pachnoda interrupta

“…Trapping has proven efficient for control in other pest species where adults are the damaging stage (reviewed by Witzgall et al 2010). PAA could be combined with previously identified host-related attractants, such as 2,3-butanediol (Bengtsson et al 2009), eugenol, and methyl salicylate (WoldeHawariat et al 2007) for evaluation of synergistic effects, and to further improve the attractiveness of lures. Such lures could be powerful instruments for monitoring, but also for mass trapping of P. interrupta.…”