In Egypt, The Nabq trees (Ziziphus spina-christi (L.)), (Family: Rhamnaceae) are considered as an important host plant having high medical economic value. These trees are attacked by many insect pests, where they seemed to be the sole recorded host plant of the monophagous fruit fly species; the Zizyphus fruit fly Carpomyia incompleta Becker (Diptera: Tephritidae) from the viable literatures A field study was performed to survey the population dynamics of the pest in the three different districts (Shandaweel, Gohena, and Balasfora) in Sohag Governorate, during two periods at the beginning of the fruit maturation from March to June (in the first period) and from September to November (in the second period), in the two successive season 2016 and 2017. The obtained results indicated that the Ziziphus fruit fly was found to be parasitized by the common parasitoid Psyttalia (Opius) concolor Sźepl. (Hymenoptera: Braconidae). However, the general sex ratios obtained between (the pest and the commonly recorded parasitoid), clearly indicated these ratios were greatly towards females than males in the case of both the pest and the parasitoid. Where the occurrence of the parasitoid was related was that of its insect host during two periods of the beginning of the fruit maturation. Magnifying this natural role of the parasitoid P. concolor becomes necessary in order to encourage this beneficial agent to do its role and decrease the degree of infestation by the Zizphus trees or other fruit trees that may be subjected to the Zizphus fruit fly attack to an acceptable level. Moreover, this parasitoid could be laboratory mass-reared and released against the pest on the Zizphus trees or other fruit trees that are subjected to attack by the other common fruit flies and must be taken into consideration when applying I.P.M. programs (including the use of the biological control techniques). So, the Ziziphus trees are considered as a suitable host plant acting as a natural resource or reservoir for the parasitoid P. concolor that attacks the Ziziphusfruit fly.