Effect of Drosophila suzukii on Blueberry VOCs: Chemical Cues for a Pupal Parasitoid, Trichopria anastrephae

Abstract

Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to nd their hosts. Although, this chemical landscape may be altered by the invasion of exotic insect species. The spotted-wing drosophila (SWD), Drosophila suzukii (Diptera: Drosophilidae), is a highly polyphagous fruit pest native to eastern Asia and recently arrived in South America. The aim of our study was to characterize the effect of SWD attack on the volatile organic compounds (VOCs) of blueberries, a common host fruit, and to correlate these odor changes with the olfactory-mediated behavioral response of resident populations of Trichopria anastrephae parasitoids. Using fruit VOC chemical characterization followed by multivariate analyses of the odor blends of SWD-attacked blueberries, we showed that the development of SWD immature stages inside the fruit generates a different odor pro le than control fruits (physically damaged and free of damage). These differences can be explained by the diversity, frequency and amounts of fruit VOCs. The behavioral response of female parasitic wasps showed that T. anastrephae has an innate attraction to volatile cues from infested host fruits, which may lead to successful location of their insect host. Since resident parasitoids are able locate this novel potential host, biological control programs using local populations may be plausible as a SWD control strategy.

Trichopria anastrephae: A Promising Neotropical-Native Parasitoid for Drosophila suzukii Control

“…There was only host switching to D. suzukii when the host ratio was 80-90% D. suzukii over D. melanogaster. These findings are supported by differences in the evolutionary history between T. anastrephae and both hosts because it is a Neotropical-native parasitoid species [66] coevolved in sympatry with saprophytic drosophilid species, such as those of the D. melanogaster group [26]. This may account for the close trophic association between T. anastrephae and non-pest saprophytic drosophilids, whereas a new trophic association was recently established with D. suzukii.…”

“…Thus, T. anastrephae can parasitize D. suzukii puparia in less competitive microhabitats, such as the ground beneath fallen feral peaches and guavas in non-crop areas [35]. Previous studies have shown that most D. suzukii larvae pupate on the ground beneath fallen fruit [57][58][59][60][61][62][63][64][65][66][67][68], and puparia can be attacked by pupal parasitoids [56,69]. These earlier published data, plus information from the current study, reveal that T. anastrephae may exert mortality over D. suzukii puparia isolated on the ground.…”

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“…They also serve as a deterrent and cause behavioral changes in pests (Dicke & Baldwin, 2010;Gebreyesus Gebreziher, 2020;War et al, 2011). Recently, a study showed that the VOCs emitted by a blueberry infected with SWD were more attractive for a parasitoid than when the blueberry was not attacked (de la Vega et al, 2021).…”

Olfactory responses of Drosophila suzukii parasitoids to chemical cues from SWD-infested fruit

“…SWD parasitoids need to find SWD-infested fruit and presumably exploit fruit volatiles as cues, a tritrophic interaction that is not well understood and may be key for successful biological control. The study of these interactions have included the behavioural assessment of wasps in olfactometer tests in response to natural volatile blends from infested fruit (Biondi et al, 2021;de la Vega et al, 2021;Wolf et al, 2020). Because these are complex and dynamic volatile blends, separating its components and evaluating their ecological significance may be useful to further characterize these interactions.…”