Different concentrations of three essential oil extracts (0.5, 1, 2, 3 and 4%) were used against Tetranychus urticae.
(Koch) Chamomile; Chamomilla recutita (L.), proved to be the most efficient agent against T. urticae followed by
Marjoram; Marjorana hortensis (L.), and Eucalyptus (Eucalyptus sp.) The LC50 values of these oils were 0.651 &1.17;
1, 84 & 6.26 and 2.18 & 7.33 for adults and eggs, respectively. Herein, the bioassay experiments of the two essential
oils, Chamomile and Marjoram showed relationship between essential oil contents and activity of enzyme glutathione
S-transferase, non specific esterase and alkaline phosphatase in T.urticae. GC-MS analysis of C. recutita and M.
hortensis proved the presence of 13 and 14 essential oil components, respectively. The major essential oil contents of C.
recutita are α-Bisabolol oxide A (35.25%), and Trans-β-farersene (7.98%), while the main components of M. hortensis
are Terpinen-4-ol (23.86%), P-cymene (23.40%) and Sabinene (10.90%). The major components of both plant extracts
(Terpinen-4-ol 23.86% and α-Bisabolol oxide A 35.25% essential oils) may be responsible for the activity of enzymes
of T. urticae (glutathione S-transferase, non specific esterase and alkaline phosphatase).