Courtship and mating traits of Tenebrio molitor and Sitophilus zeamais are impacted by sublethal concentrations of carlina oxide

Tenebrio molitor L. (Coleoptera: Tenebrionidae) and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) are harmful pests in storages. Carlina acaulis L. (Asteraceae) is a medicinal plant used for its beneficial effects throughout Central and Eastern Europe. The essential oil (EO) of this plant, almost entirely made up of carlina oxide, exhibited broad-spectrum properties, including notable pesticidal activity against vectors and agricultural or stored-product pests. This research examined the impact of sublethal concentrations of carlina oxide on the mating behavior of T. molitor and S. zeamais. Sitophilus zeamais adults were more sensitive to carlina oxide than T. molitor adults, as LC₁₀, LC₃₀, and LC₅₀ values were lower. The mating success of T. molitor and S. zeamais was impacted negatively by the exposure of both beetles to sublethal concentrations (LC₁₀ and LC₃₀) of carlina oxide. For both species, the mean duration of each mating phase was significantly affected by exposure to sublethal concentrations of carlina oxide vs. control. The highest mean duration of copulation was recorded in control pairs, which was significantly longer than pairs treated with LC₁₀ and LC₃₀. Concerning lateralization, males of both species showed a left-biased trend, which led to higher successful copulations than right-biased, front or back-side males, regardless of treatment or control. Overall, carlina oxide alters the behavioral traits of T. molitor and S. zeamais, thus, it should be further considered in Integrated Pest Management (IPM) approaches in the storage environment.