Fruit trees are susceptible to infestations from a variety of harmful pests during developing and growth stages, include striped mealybug, Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae). The current study aims to assess effectiveness of three essential-oils: namely, Thyme, Thymus vulgaris L. , Flaxseed, Linum usitatissimum L. , and Lemon, Citrus limon L. on nymphal and adult populations of F. virgata at concentrations (5000, 10000, 15000, and 20000ppm) under laboratory conditions. The oil effects on detoxification enzymes “Acetylcholinesterase AchE., glutathione S-transferase activity and energy reserves (Proteins, carbohydrates, and lipids) at LC₅₀-concentration were also tested. Data obtained indicated that, the highest mortality% of mealybug nymphs and adults was estimated at high concentration (20000) after 24 and 48 hrs. Mortalities were varied according to concentration and type of essential-oil. Lemon-oil was most effective with LC₅₀-values (2309.65 and 50.28 ppm) followed-by thyme-oil (2921.49 and 170.00 ppm) and flaxseed-oil (3999.38 and 528.64 ppm), against nymphs after 24 and 48 hrs., respectively, while they were (542.89 and 39.74), (689.47 and 77.67) and (1621.21 and 341.88 ppm) against adults, respectively. Biochemical analyses showed that, essential-oils caused a significant reduction in activity of glutathione S-transferase and induction in activity of acetylcholine esterase on F. virgata. In general, results demonstrated that, high-toxicity was reached by two formulated-oils “Thyme and Lemon" against nymph and adult of F. virgata. Therefore, this study suggests use these essential-oils as safe compounds in IPM-strategy of mealybugs.