Bioactivity of Carlina acaulis Essential Oil and Its Main Component towards the Olive Fruit Fly, Bactroceraoleae: Ingestion Toxicity, Electrophysiological and Behavioral Insights.

Roberto Rizzo,Loredana Cappellacci,Angelo Canale,Giacinto Salvatore Germinara,Filippo Maggi,Milko Sinacori,Marco Pistillo,Valeria Zeni,Gabriella Lo Verde,Eleonora Spinozzi,Giovanni Benelli,Riccardo Petrelli

doi:10.3390/insects12100880

Abstract

Simple SummaryIn recent years, botanical insecticides based on essential oils (EOs), or their main components, have received much attention as promising tools for Integrated Pest Management, due to their environmental safety and low side effects on non-target organisms. In this study, Carlina acaulis EO and its main component, carlina oxide, recently proven to be effective larvicidal and adulticidal agents against some insect pests, were analyzed for their toxicity, electroantennographic (EAG), and behavioral responses to adult olive fruit fly (Bactrocera oleae). The C. acaulis EO was more toxic to the tephritid than the carlina oxide, and both were more toxic to the same insect pest than EOs from other plant species tested in previous studies. The EAG responses evoked by the EO were significantly higher than those elicited by the carlina oxide. Carlina oxide did not lead to attraction or repellency responses in B. oleae males and females. Overall, our results highlight the potential employ of C. acaulis-borne products in the development of effective eco-friendly “lure and kill” formulations to be used in tephritid management.Among botanical insecticides based on essential oils (EOs) or their main components, Carlina acaulis EO and the aromatic polyacetylene carlina oxide, constituting more than 90% of its EO, were recently proven to be effective against the larvae and adults of some insect vectors and pests. In this study, the toxicity of C. acaulis EO and carlina oxide were tested on Bactrocera oleae adults using a protein bait formulation. The LC50 values of the C. acaulis EO and carlina oxide were 706 ppm and 1052 ppm, respectively. Electroantennographic (EAG) tests on B. oleae adults showed that both carlina EO and oxide elicited EAG dose-dependent responses in male and female antennae. The responses to the EO were significantly higher than those to carlina oxide, indicating that other compounds, despite their lower concentrations, can play a relevant role. Moreover, Y-tube assays carried out to assess the potential attractiveness or repellency of carlina oxide LC90 to B. oleae adults showed that it was unattractive to both males and females of B. oleae, and the time spent by both sexes in either the control or the treatment arm did not differ significantly. Overall, this study points out the potential use of C. acaulis EO and carlina oxide for the development of green and effective “lure-and-kill” tools.

Highlights

Carlina acaulis L. (Asteraceae) is a traditional medicinal plant growing in the calcareous mountainous soils of central-southern and eastern Europe and is currently used in herbal products and as a food [1,2]
The GC-MS analysis of the C. acaulis essential oils (EOs) revealed the predominance of carlina oxide (97.7%) in the mixture (Figure 1A), while the remaining identified fraction was composed of the aromatic benzaldehyde (1.4%), the sesquiterpene hydrocarbons ar-curcumene (0.7%) and β-sesquiphellandrene (0.1%)
The present study showed that C. acaulis EO and carlina oxide are highly toxic to both sexes of the olive fruit fly when incorporated in protein baits, with both products achieving a significant concentration-dependent effect

Summary

Introduction

Carlina acaulis L. (Asteraceae) is a traditional medicinal plant growing in the calcareous mountainous soils of central-southern and eastern Europe and is currently used in herbal products and as a food [1,2]. The main constituent of its essential oil (EO) is the aromatic polyacetylene carlina oxide (>90%) [2,3], known as 2-(3-phenylprop-1-ynyl)furan. Polyacetylenes deserve particular attention for their promising biological activities [5] They play a role as phytoalexins, as they contain antifeedant, insecticidal, nematocidal, antimicrobial, and phytotoxic properties [6,7]. Both C. acaulis EO and carlina oxide were recently proven to be important larvicidal and adulticidal agents, being highly effective against the filariasis vector, Culex quinquefasciatus Say (Diptera: Culicidae), and the housefly, Musca domestica L. Once formulated in protein baits, the C. acaulis EO was toxic to Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) adults, and affected their aggressive behavior at sublethal concentrations [12]

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