EN
Perennial crops such as short rotation willow (Salix viminalis) are cultivated on the same field for many years. Without cultivation measures a monoculture provides a perfect habitat for the development of pests. The study on pests occurrence on different willow clones and cultivars was conducted on Research Centre for Cultivar Testing collection in Śrem from 2009 to 2010. The percentage of plants infected by the most economically important pests was recorded and analyzed. Phratora vulgatissima L., Earias chlorana L. oraz Dasyneura marginemtorquens Winn. Belonged to the insect pest considerably reducing fresh biomass by feeding on the host plants.