Potential use of essential oils from Origanum vulgare and Syzygium aromaticum to control Tetranychus urticae Koch (Acari: Tetranychidae) on two host plant species

Plant extracts and essential oils are considered alternatives to synthetic chemicals with toxic effects on insects and mites. Acaricidal, repellent, and oviposition effects of commercially available essential oils of Origanum vulgare L. (Lamiaceae) and Syzygium aromaticum (L.) (Myrtaceae) were investigated in this study on Tetranychus urticae Koch (Acari: Tetranychidae), one of the main pests in agriculture, on two host plant species using leaf disc bioassays. O. vulgare essential oil showed higher toxicity to T. urticae protonymphs and adult females inhabiting both bean and tomato leaves than S. aromaticum essential oil. The LC(50) values of O. vulgare essential oil were found to be 1.67 and 2.05 µl L(−1) air for the bean populations in protonymphs and adult females and 1.87 and 3.07 µl L(−1) air for the tomato populations, respectively. Five percent concentration of S. aromaticum essential oil had the highest repellent effect on the bean population of T. urticae after 1, 24, and 48 h, resulting in 61.22%, 40.81%, and 18% repellence, respectively. Although O. vulgare showed higher toxic effects, S. aromaticum was a better repellent against the bean population of T. urticae. The mortality rates of adult females of T. urticae treated with either O. vulgare or S. aromaticum essential oil increased with the increasing concentration and time on both host plants. Both essential oils caused a decrease in egg number and larvae hatching in both bean and tomato populations of T. urticae. In the light of the results obtained, O. vulgare and S. aromatium essential oils have the potential to be used in the control programs against T. urticae in both host plants.