The application of the preparation Actara 25-WG in the control of larvae and adult Chrysomela populi L., which are a serious problem in poplar cultivation, was tested in poplar rooting-bed in the Experimental Station of the Poplar Research Institute in Novi Sad and in the laboratory conditions. The efficiency of the preparation in the suppression of larvae was tested in the field experiment, while the intestinal and contact effect of the preparation on adult pests was tested in two separate experiments in the laboratory. The study results point to the possibility of successful application of the preparation Actara 25-WG in the control of big poplar leaf beetle larvae and adults.