Potential of essential oils against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

The two-spotted spider mite (TSSM), Tetranychus urticae poses a significant threat to ornamental plants. Traditional control relies heavily on synthetic acaricides, therefore there is a need to identify new environmentally friendly active ingredients. We hypothesized that using essential oils from plants known for their insecticidal properties might be an alternative method to control TSSM. This study aimed to (a) evaluate the impact of various concentrations of essential oils on mortality, oviposition, and egg viability, (b) establish the lethal dose and lethal concentration for these essential oils, and (c) conduct an analysis of their potential phytotoxicity. Manuka, copaiba, ginger, pepper tree, and tea tree were identified as potential options against TSSM, and each oil was tested at four concentrations: 0.01%, 0.1%, 1%, and 10%. The control treatment consisted of absolute ethanol. The experimental unit was one TSSM sprayed with 1 mL of solution of the assigned treatment. The mortality and the number of eggs were recorded after 24 and 48 hours. At 48 hours the females were removed, and the eggs were left. Manuka oil at 10% concentration resulted in the highest mortality in comparison to the other treatments. The lowest oviposition was recorded for manuka oil at 1% and 10%. No significant differences were observed for the proportion of egg viability. Further analysis is underway to determine LD50, LC50, and phytotoxicity. Preliminary findings suggest that manuka oil has potential for TSSM control, with mortality observed within 24 hours, followed by copaiba and pepper tree oils at higher concentrations.