Repellent effect of santalol from sandalwood oil against Tetranychus urticae (Acari: Tetranychidae).

Thirty-four essential oils were screened for their repellent activities against the twospotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae), at 0.1% concentration level using choice and no-choice laboratory bioassays. Of these, 20 essential oils showed significant repellencies against T. urticae in the choice tests. In subsequent no-choice tests using these 20 essential oils, only sandalwood oil showed significant repellency against T. urticae. Total number of eggs oviposited by T. urticae was significantly lower than controls in the choice tests when the kidney bean leaves were treated with 1 of 14 essential oils. The significant repellency of sandalwood oil against T. urticae lasted at least for 5 h at the 0.1% concentration level. Our GC-MS analysis indicated that the major components of the sandalwood oil were alpha-santalol (45.8%), beta-santalol (20.6%), beta-sinensal (9.4%), and epi-beta-santalol (3.3%). Santanol, a mixture of the two main components in the sandalwood oil, appears to be responsible for the repellency of sandalwood oil against T. urticae.