author(s)
Mohamed BRAHAM and Nidhal AMOR

abstract
In this study, a one-year field experiment was conducted to evaluate the effect of winter tree pruning severity on the abundance, population dynamics and shoot infestation as well as vegetative growth of two citrus cultivars Clementine, C. clementina Hort. Ex Tan. and orange, Citrus sinensis cv Thomson by the Spirea aphid, Aphis spiraecola Patch (Hemiptera, Aphididae) and its natural enemies. Data were collected during the spring in 2015 on 6-years old Citrus trees submitted to 3 different intensities pruning (severe, medium or control and light pruning) following a completely randomized design with five replications in which one single tree-plot was considered as a replicate. Results showed that, for both Citrus cultivars, pruning enhanced the sprouting of newly shoots, the shoot elongation and the number of leaves per shoot especially for Clementine cultivar. The average number of newly growing shoots per tree was maximum in heavy pruned trees (5593±315 shoots per tree) and minimum in lightly pruned trees (2656±855shoots per tree). There was a positive relationship between the number of new shoots per experimental tree and A. spiraecola infestation. The trees severely pruned were more infested by larvae, wingless and winged aphids even though this difference may be shifted when the population densities increased exponentially. The densities of aphid natural enemies show mixed results for C. clementina but were similar for C. sinensis.