Exploring essential oils of Slovak medicinal plants for insecticidal activity: The case of Thymus alternans and Teucrium montanum subsp. jailae.

Thymus alternans and Teucrium montanum subsp. jailae are medicinal and aromatic plants, typical of Slovakian flora, producing bioactive essential oils. In the present study, we evaluated the insecticidal potential of the essential oils, obtained by hydrodistillation from the plant aerial parts and analysed by GC-MS, as insecticidal agents. For the purpose, they were assayed against three insect species acting as agricultural pests or vectors of medical relevance, such as the common housefly, Musca domestica L., the lymphatic filariasis vector, Culex quinquefasciatus and the Egyptian cotton leafworm Spodoptera littoralis; α-cypermethrin was tested as positive control. The two essential oils exhibited a different chemical profile, with monoterpenes and sesquiterpenes being the main fractions in the essential oils from Th. alternans and T. montanum subsp. jailae, respectively. Insecticidal tests showed that the T. montanum essential oil was effective against S. littoralis (LD50(90) = 56.7 (170.0) μg larva-1) and Cx. quinquefasciatus larvae (LC50(90) = 180.5 (268.7) mg L-1), whereas T. alternans essential oil displayed good toxicity against M. domestica adults (LD50(90) = 103.7 (223.9) μg adult-1). Overall, our results add useful knowledge about the potential of Slovakian flora as a source of botanicals for the eco-friendly management of insect pests and vectors.