In the experiment the population dynamics as well as the development of Myzocallis caryli on five hazel cultivars were investigated. In terms of host plant resistance to Myzocallis caryli the tested cultivars displayed very similar susceptibility. The obtained results show that no significant differences were found in aphid rm. In spite of this, due to the longest prereproductive time, the lowest fecundity and the smallest number of aphids per 10 leaves, Kataloński is less suitable cultivar for the aphids from all tested hazel cultivars.

In four years’ experiment the infestation of hazel nuts by hazelnut weevil was investigated. Significant differences in resistance of different hazelnut cultivars were found. Olbrzymi z Halle cultivar exhibited a moderate resistance to the pest and was classified to the III class, while other cultivars showed a moderate susceptibility to the pest and were classified to class IV.

During the years of observations pedatory arthropods of Arachnida, Chrysopidae, Heteroptera, Coccinellidae, and Syrphidae were collected from Myzocallis coryli Goetze colonies. Arachnida constituted the most numerous group followed by predatory bugs of Heteroptera.