The Effects of clove, Syzygium aromaticum essential-oil against spider-mite Tetranychus urticae, Koch was estimated in lab and semi-field conditions. Treated adult-females conducted by different concentrations of clove essential oil (eugenol) concentrations using spraying method for 1, 3 and 7 days. Mortality was measured upon treatment with three concentrations of 0.25, 0.50 and 1.0% V/V. Female mortality increasing with increasing concentrations and LC₅₀ value was calculated. Moreover, all the tested concentrations of the essential oil were significant. The effect of LC₅₀ of eugenol on the neuronal-enzymes acetylcholine-esterase “AchE" and alkaline-phosphatase “ALP" of spider-mites were investigated on 24 hours and 3 days post-treatment. The obtained data resulted the activity of “AchE" and “ALP" showed decreasing after treatment on 24 hours by clove-oil while, “ALP" showed increasing on 3-days post-treatment. The evaluation of clove essential oil effect in semi-field condition on “T. urticae", results indicated that it gave satisfying results whereas 92 % population reduction respectively. Finally, we can conclude that clove essential oil was achieved good results to control this spider mites.