Fumigant toxicity of some essential oils on Tetranychus urticae (Acari: Tetranychidae)

Tetranychus urticae Koch (Acari: Tetranychidae) is an economically important pest of agricultural and ornamental crops worldwide. It has been shown that many of natural plant-based pesticides have fewer side effects compared with synthetic chemicals. This study was aimed at assessing the fumigant toxicity of five essential oils to eggs and adult females of T. urticae. Essential oils were extracted from leaves and fruits of Eucalyptus microtheca F. Muell., leaves of Satureja sahendica Bornm., fruits of Heracleum persicum Desf. and seeds of Foeniculum vulgare Mill. The experiments were done using bean leaf discs through filter paper diffusion bioassay without allowing direct contact in 4 l plastic containers. The study was conducted in laboratory at 26 +/- 2 degrees C, 50 +/- 10% RH and 16: 8 (L: D) h photoperiod. Exposure times for the adults and eggs were 24 and 72h, respectively. LC50 values for the adult females were 1.52, 5.70, 0.98, 3.15 and 5.75l/l for E. microtheca leaves, E. microtheca fruits, S. sahendica, H. persicum and F. vulgare, respectively. For these oils, LC50 values for eggs were 0.56, 2.36, 0.54, 1.53 and 1.17l/l, respectively. The data suggest that essential oils of E. microtheca and S. sahendica leaves have the potential to be used in management of two spotted spider mite in greenhouse conditions provided that they produce similar results in whole plant experiments as well.