Carlina acaulis essential oil: a candidate product for agrochemical industry due to its pesticidal capacity

Carlina acaulis L. is a herb mainly used in central Europe as traditional medicine or food. Recently, C. acaulis essential oil (EO) and its nanoemulsion showed elevated efficacy against several insects of medical and agricultural importance. In the current study, efficacy of C. acaulis EO was estimated against several stored product pests. The EO was sprayed on wheat to control Acarus siro L. (adults, nymphs), Alphitobius diaperinus (Panzer) (adults, larvae), Oryzaephilus surinamensis (L.) (adults, larvae), Rhyzopertha dominica (F.) (adults), Sitophilus oryzae (L.) (adults), Tenebrio molitor L. (adults, larvae), Tribolium castaneum (Herbst) (adults, larvae), and Tribolium confusum Jacquelin du Val (adults, larvae). Carlina acaulis EO was mainly composed by carlina oxide (98.8%), with benzaldehyde (1.2%) and ar-curcumene (traces) as minor components. Both adults and nymphs of A. siro showed high mortality, i.e., 91.1 and 95.6%, after 7 days of initial exposure to 1000 ppm (1000 μL C. acaulis EO/kg wheat), respectively. This concentration provided the death of 25.6% of the exposed A. diaperinus adults at the termination of trials. Total mortality (100.0%) of A. diaperinus larvae was reached 2 and 4 days after initial exposure on wheat sprayed with 1000 and 500 ppm of C. acaulis EO, respectively. One thousand (1000) ppm of EO killed 96.7% of O. surinamensis adults and all larvae 7 and 2 days after initial exposure, respectively. Concerning adults of R. dominica and S. oryzae, 1000 ppm achieved complete mortality after 4 and 6 days of initial exposure, respectively. Tenebrio molitor adults reached 81.1% mortality after their 7-days exposure to 1000 ppm C. acaulis EO. All T. molitor larvae were dead after 7 or 4 days of initial exposure to 500 and 1000 ppm, respectively. Carlina acaulis EO caused 97.8 and 100.0% mortality to adults of T. castaneum after 7 and 5 days of initial exposure to 1000 and 500 ppm, respectively. Complete mortality was observed after 16 h (1000 ppm) and 2 days (500 ppm) of initial exposure for T. castaneum larvae. Similarly, both examined stages of T. confusum achieved 100.0% mortality at the concentrations of 500 and 1000 ppm, after 7 and 4 days (adults), and 1 day and 16 h (larvae) of exposure, respectively. Overall, C. acaulis EO demonstrated pesticidal efficacy higher to pirimiphos-methyl, a conventional organophosphate insecticide, against a wide range of stored-product pests. Therefore this EO represents a reliable option for further developing eco-friendly and non-hazardous pest management strategies.