Аphids are the dominant pests in the complex of harmful fauna of stone fruits in Ukrane, in addition to fruit-damaging species. In plum orchards mealy plum aphid Hyalopterus pruni Geoffr. (Hemiptera: Aphidinae) cause serious economic damage. Insect predators have an important role in the regulation of agricultural pests. Our goal was to determine the role of predation in the dynamics of mealy plum aphid population. Investigations were carried out in period of mass development of mealy plum aphid in the experimental plum orchard garden of the Institute of Horticulture of Ukrainian Academy of Agrarian Sciences of Ukraine. For this purpose, model trees were selected and isolators were installed on 4 branches of each tree with aphid-infested leaves. Different species of entomophagous were placed in isolators and assesments were performed on daily basis. According to our observations, Adalia bipunctata L., A. decimpunctata L., Syrphus ribesii L., S. balteatus Deg, Chrysopa perla L., Ch. carnea Steph. dominate among aphidophagous predators. Coccinella septempunctata L., Calvia quatuordecimguttata L., Propylaea quatuordecimpunctata L. were less common. Syrphus and Chrysopa larvae have the highest predation activity. The influence of weather conditions on the efficiency of aphidophagous predators was analyzed. Optimal conditions for A. bipunctata, A. decimpunctata, S. ribesii, S. balteatus, Ch. perla, Ch. carnea during June-July were as follows: mean daily temperature -17-20°C, precipitation 0.1-1.5 mm and relative air humidity 57-67%. The threshold ratios of dominant aphidophagous predators to aphids were determined. High predation activity of Syrphus and Chrysopa larvae and coccinellides indicates that the ratio of entomophagous to aphids must be taken into account when making decision about control measures.