In respect to the forthcoming implementation of the EU directive 2009/128/EC in 2014, the Belgian Government has already compelled tree nurseries to resort to Integrated Pest Management (IPM) strategies. One of the techniques in IPM is the application of conservation biological control, i.e maximizing the biological control effects of occurring natural enemies. Providing habitats such as flower strips and hedgerows could encourage the natural enemies and increase their abundance in the adjacent fields. To investigate the impact of a native flower strip and hedgerow on the population density of the key pests and their natural enemies in tree nurseries, a case study on unsprayed lime trees (Tilia cordata Mill.) will be carried out during three growing seasons. Population densities on a lime tree plot bordered at one side by a flower strip or hedgerow, are compared to a control plot bordered by bare soil. These plots are located at the Research Centre for Ornamental Plants in Destelbergen, Belgium. Biweekly, monitoring of lime aphids (Eucallipterus tilliae L.) and their main natural enemies (Chrysopidae, Coccinellidae and Syrphidae) took place by visual inspection of lime trees. Leaf samples were taken for the monitoring of mites and processed with the centrifugal flotation (rust mites) or Berlese funnel technique (remaining mites). During the first year of the study, no significant differences were found between plots in the number of lime aphids, coccinellids and syrphids. Chrysopids, on the other hand, were more abundant in the plot adjacent to the flower strip compared to the control plot. In addition, rust mites (Aculus ballei Nal.) and spider mites (Tetranychus urticae Koch) were not affected by the presence of a flower strip or hedgerow. Phytoseiidae were the most encountered predatory mites. In addition, two species, i.e. Euseius gallicus Kreiter &Tixier and Paraseiulus triporus Chant & Shaul, were recorded for the first time in Belgium nurseries. As mentioned in the title, these are preliminary results, further research in time is needed to fully elucidate the impact of a flower strip or hedgerow on the biodiversity in lime trees.