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

Abstract

Among botanical insecticides based on essential oils (EOs) or their main components, <i>Carlina acaulis</i> 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 <i>C. acaulis</i> EO and carlina oxide were tested on <i>Bactrocera oleae</i> adults using a protein bait formulation. The LC₅₀ values of the <i>C. acaulis</i> EO and carlina oxide were 706 ppm and 1052 ppm, respectively. Electroantennographic (EAG) tests on <i>B. oleae</i> 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 <i>B. oleae</i> adults showed that it was unattractive to both males and females of <i>B. oleae</i>, 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 <i>C. acaulis</i> EO and carlina oxide for the development of green and effective "lure-and-kill" tools.