The present work aimed to determine the insecticidal effects of three selected essential oils (EOs) of Pogostemon cablin, Thymus vulgaris, and Citrus aurantifolia against three insect species Melolontha melolontha, Halyomorpha halys, and Pyrrhocoris apterus. EO P. cablin showed very strong insecticidal effects against M. melolontha when it inhibited the insect species by more than 50% at concentrations of 50–6.25%. Against H. halys it also showed strong insecticidal effects at concentrations of 50–12.5%. The insecticidal activity against P. apterus was significantly lower than against the other insect species tested. The insecticidal activity of at least 50% was only observed at a concentration of 50%. EO T. vulgaris showed very strong insecticidal activity against M. melolontha which reached at least 50% at concentrations of 50–6.25%. When tested for its effect against H. halys, high efficacy was observed at concentrations of 50–12.5%. Against P. apterus, the efficacy was the lowest as 50% insecticidal activity was observed only at concentrations of 50% and 25%. EO C. aurantifolia showed only weak insecticidal activity against M. melolontha where the highest concentration tested killed 50% of the individuals. The very weak insecticidal activity was observed against H. halys where none of the tested concentrations had efficacy higher than 50%. The most pronounced effect of EO C. aurantifolia was observed against P. apterus where concentrations of 50% and 25% killed more than 50% of individuals. All tested EOs showed insecticidal effects and could potentially represent a natural alternative to synthetic insecticides.
