Development of a Phytochemical-Based Lure for the Dried Bean Beetle Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae)

Abstract

The dried bean beetle, Acanthoscelides obtectus, is an economically important, worldwide pest of legume crops including dry beans, Phaseolus vulgaris. Assessment of A. obtectus infestation levels in pre-harvest field crops and post-harvest granaries is difficult to achieve because there is no effective monitoring tool for early detection so that interventions can be deployed as needed. Because A. obtectus is a generic pollen and nectar feeder, we adopted an electrophysiological (EAG) screening approach, using the antennae of female A. obtectus to identify physiologically active, volatile phytochemicals, which could then be investigated for their attractiveness to A. obtectus in laboratory behavioral assays and preliminary field tests. Of the 27 compounds tested in EAG screening, 5 compounds, i.e., methyl anthranilate, methyl eugenol, benzyl alcohol, (RS)-lavandulol, and 2-phenylethanol, elicited stronger EAG responses than the standard (1-phenylethanol). In 4-arm olfactometer bioassays, female A. obtectus preferred the olfactometer arm containing the odor of either methyl anthranilate or benzyl alcohol compared to the solvent control. In preliminary field tests using these 2 compounds as a binary mixture, at least 5 times as many beetles were caught on baited traps compared to non-baited traps. The field data also suggested that benzyl alcohol was primarily responsible for the field activity of the blend. We hypothesize that the attraction of A. obtectus to the combined benzyl alcohol/methyl anthranilate and the single benzyl alcohol baits is connected to the species` nectarand pollen-feeding behaviour and not to its intraspecific communication. To our knowledge, this is the first evidence that A. obtectus behavior in the field can be modified by the deployment of plant-derived semiochemicals.

A semiochemical view of the ecology of the seed beetle Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae, Bruchinae)

“…Because it visits several flowering plant species, Vuts et al (2021) assumed that volatiles shared across the floral bouquet of the nectar plants favoured by A. obtectus are suitable candidates as generic attractants. Of the 27 compounds screened in EAG, five elicited sufficiently large antennal responses to be considered for further testing in olfactometer assays.…”

“…Traps used in the field experiments in Vuts et al (2021) caught only between 87 and 153 individuals in total, which may reflect usual population sizes in the study area (East Hungary) and also highlights the need for a wide-range trapping campaign once the optimal trap design and lure composition are available. Although considered as a somewhat cruder approach than the traditional sequence of plant headspace analysis and identification of bioactive constituents (Bruce et al, 2011;Tewari et al, 2015), EAG and behavioural (laboratory and field) screening of a panel of candidate compounds has proven to be an effective way of discovering semiochemicals.…”

A Faboideae-Specific Floral Scent Betrays Seeds to an Important Granivore Pest

“…1 The scent produced by flowers, particularly, appears to be a predominant cue for insect herbivores to locate potential foraging sites. 1,8 For example, both lepidopteran and coleopteran legume pod borers have been shown to be highly attracted to the flower scents of their host plants 9,10 as several hemipteran species. 11 Yet, to maximize host finding success using odor cues, insect granivores need to adapt their development to the phenology of the host plant.…”

“…In addition, the immature and adult stages of several insect granivores, such as stink bugs or curculionid beetles, can directly forage on the seeds that are still attached to the plant. , Those insect species are generally host-specific and can locate the spatially and temporally aggregated seed resource using visual and odorous cues produced by the host plants . The scent produced by flowers, particularly, appears to be a predominant cue for insect herbivores to locate potential foraging sites. , For example, both lepidopteran and coleopteran legume pod borers have been shown to be highly attracted to the flower scents of their host plants , as several hemipteran species . Yet, to maximize host finding success using odor cues, insect granivores need to adapt their development to the phenology of the host plant .…”

Special Issues in Honor of Professor Dr. Dr. hc mult. Wittko Francke, 28 November 1940 - 27 December 2020

“…Among many other collaborations with Zarbin's group, Professor Francke worked directly on the identification of pheromones for several South American weevil species. The subsequent paper (Vuts et al 2021) reflects Professor Francke's longterm collaboration with the Hungarian research team headed by Miklós Tóth and Gábor Szőcs, and now being continued by their academic progeny. This paper, examining responses of the dried bean weevil to host plant volatiles, builds on previous work in which Professor Francke helped the team to identify missing components of the dried bean weevil pheromone.…”