Effects of Aqueous Plant Extracts on Adult Females Tetranychus urticae Koch (Acari: Tetranychidae)

The Two-spotted spider mite, Tetranychus urticae Koch,1836 (Acari: Tetranychidae), reduces quality and yield in cultivated plants. The most widely employed method for controlling this mite is the application of chemical acaricides. However, over time, researchers have focused on the adverse effects such as resistance, side effects on beneficial organisms, and environmental issues. In this laboratory study, the acaricidal effects of aqueous extracts of Juglans regia, Dieffenbachia amoena, Lantana camara, Eucalyptus globulus, and Nerium oleander against T. urticae were investigated. Plant extracts at concentrations of 1%, 3%, 6%, and 12% (v/v) were applied to T. urticae adult females using leaf dipping and spraying methods. The numbers of dead and live individuals were evaluated 24, 72, and 144 hours after the applications. In the dipping method, the highest contact effect was obtained in J. regia and D. amoena at 12% concentration at 99.6 and 94.5%, respectively, 144 hours after treatments. Conversely, at the same time and at 1% concentration, L. camara extract exhibited a low contact effect of 20.68%. Juglans regia extract at 12% concentration showed the highest effect and reached a 71% mortality rate at the end of 24 hours in the dipping method, The lowest effect (10.8% mortality rate) was obtained with L. camara at 1% concentration, and the same duration. Dieffenbachia amoena showed the highest toxicity with an LC50 value of 2561 mg L-1 in the spraying method, while the lowest toxicity was found in the E. globulus application (4388 mg L-1). This study revealed that aqueous plant extracts showed toxic effects on T. urticae.