Contributions of γ-Aminobutyric Acid (GABA) Receptors for the Activities of Pectis brevipedunculata Essential Oil against Drosophila suzukii and Pollinator Bees.

The γ-aminobutyric acid (GABA) receptors play pivotal roles in the transmission of neuronal information in the nervous system of insects, which has led these proteins to be targeted by synthetic and natural products. Here, we assessed the insecticidal potential of the essential oil of Pectis brevipedunculata (Gardner) Sch. Bip., a neotropical Asteraceae plant used in traditional medicine, for controlling Drosophila suzukii (Matsumura) adults by feeding exposure. By using in silico approaches, we disentangle the contribution of GABA receptors and other potential neuronal targets (e.g., acetylcholinesterase, glutathione-S-transferases) in insects that may explain the essential oil differential activities against D. suzukii and two essential pollinator bees (Apis mellifera Linnaeus and Partamona helleri Friese). Neral (26.7%) and geranial (33.9%) were the main essential oil components which killed D. suzukii with an estimated median lethal concentration (LC50) of 2.25 µL/mL. Both pollinator forager bee species, which would likely contact this compound in the field, were more tolerant to the essential oil and did not have their diet consumptions affected by the essential oil. Based on the molecular predictions for the three potential targets and the essential oil main components, a higher affinity of interaction with the GABA receptors of D. suzukii (geranial -6.2 kcal/mol; neral -5.8 kcal/mol) in relation to A. mellifera (geranial -5.2 kcal/mol; neral -4.9 kcal/mol) would contribute to explaining the difference in toxicities observed in the bioassays. Collectively, our findings indicated the involvement of GABA receptors in the potential of P. brevipedunculata essential oil as an alternative tool for controlling D. suzukii.

Potential of Ocotea indecora Essential Oil for Controlling Drosophila suzukii: Molecular Predictions for Toxicity and Selectivity to Beneficial Arthropods.

The protection of soft-skinned fruits against Drosophila suzukii has relied primarily on the efficacy of a few synthetic molecules. Despite their short-term efficacy, these molecules can cause environmental pollution, unintendedly affect non-target organisms, and fail to provide sustainable control. The shortfalls of using synthetic pesticides warrant the search for alternatives, such as essential oils extracted from plants, with greater eco-friendlier properties. Here, we chemically characterized and evaluated the toxicity of the essential oil extracted from leaves of Ocotea indecora (Schott) Mez (Lauraceae) against D. suzukii via two exposure pathways (ingestion and contact). We also assessed the selectivity of the essential oil to two predatory natural enemies, Eriopis connexa and Chrysoperla externa and two pollinator bees, Apis mellifera and Partamona helleri. In addition, we conducted in silico predictions to investigate potential interactions between the major compound of the essential oil and the insects' transient receptor potential (TRP) channels. Our chromatographic analysis revealed sesquirosefuran (87%) as the major compound. Higher toxicity to adults of D. suzukii was observed in contact exposure (LC50 = 0.43 µL mL-1) compared to ingestion (LC50 = 0.72 µL mL-1). However, the essential oil did not cause mortality to the non-target organisms tested here, even when applied at 2.20 µL mL-1. Molecular predictions demonstrated that sesquirosefuran binds more stably to the TRP channels of D. suzukii than to those expressed in beneficial arthropods. Collectively, our findings provide the initial framework for the potential use of O. indecora essential oil as a sustainable alternative for managing D. suzukii infestations.

The Potential of Plant-Based Biorational Products for the Drosophila suzukii Control: Current Status, Opportunities, and Limitations.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive species that causes serious damage to soft-skinned fruits. The use of plant-based biorational insecticides (plant extracts and essential oils) to control this pest has grown extensively. We conducted a systematic review and meta-analysis to examine the current status, trends, and perspectives of these studies, with a focus on the plant families and major compounds used as insecticides to control D. suzukii. The first article in this research field was published in 2015, and there has been exponential growth in subsequent years. Thirty-six botanical families were studied in these articles, with a prevalent interest in Myrtaceae and Lamiaceae plant species. The major constituents of these plant-based biorational molecules belong to monoterpenoids, followed by monoterpenes, benzene derivatives, and others. Geranial was the most frequent major constituent of these plant-based compounds. Our analysis revealed a few crucial consequences of the bias provided by the investigations using plant-based biorational insecticides for controlling D. suzukii. Firstly, there is a major focus on the pest species, with little or no attention paid to undesired effects on non-target beneficial organisms (e.g., pollinator bees, predators; parasitoids) and non-target pests. Secondly, the poor knowledge of how these plant-based biorational insecticides act on target and non-target organisms. Finally, there is a need to assess the efficacy of these substances under field conditions. Thus, attention is needed to address these gaps so that plant-based biorational insecticides can become a viable pest management tool for controlling D. suzukii.