This work aimed to evaluate the efficacy of modified atmosphere (MA) enriched with Argon gas as an alternative measure for controllingfour stored dates pests, two from order: Lepidoptera, Ephestia cautella (Walker) & Plodia interpunctella (Hübner) and two from order Coleoptera; Oryzaephilus surinamensis Linnaeus & Stegobium paniceum (L.) and its effect on some enzymes activity of tested insects. Argon gas concentrations of (60, 80 and 100 %) had been tested against the four mentioned insects at different exposure times ranged from 3 to 144 hrs. The results revealed that Lepidopterous were more sensitive to Argon gas than Coleopterous. Also, data indicated that not all tested insects have the same sensitivity to Argon gas. Obtained results indicated that the reduction % of adult emergence increased by increasing exposure duration and or concentration. At the concentration of 100 % Argon, data reported that the larvae of E. cautella were the most susceptible and reached a 100% reduction after 12 hrs. While the adults of O. surinamensis was the most tolerant insect stage to Argon gas where reached 74.60 % reduction after 72 hrs. Exposure of P. interpunctella and O. surinamensis to LT 50 of Argon increased the activity of two defensive enzymes within tested insects, Acid phosphatase, &Carboxlesterases.  and decreased the activity of LDH enzyme.