Number of hairs on abaxial leaf surface of 13 apple cultivars differed significantly. The most hairs per 1 cm² on abaxial surface were on cvs. Lodel (2,578.3) and Jonafree (2,462.2). Leaves of cultivars Antonówka and Novamac had the least number of hairs (1,054.4; 1,285.7; respectively). Correlation between number of hairs on abaxial leaf surface of investigated apple cultivars and Tetranychus urticae (Koch) female fecundity decreased during 10 first days of their lives. Along with increased number of hairs, the fecundity of this species declined.

Apple cultivars investigated as new hosts for two-spotted spider mite, Tetranychus urticae Koch appeared to provide good environment for its development and reproduction. The best conditions for two-spotted spider mite development were on leaves of cultivars Novamac and Freedom with a net reproduction (R_o) 22.6 and 20.3 respectively, while the worst on cultivars Pioner and Primula with R_o 8.9 and 10.2 ,respectively.

In the years 1999-2001 occurrence of eriophyoid mites (Eriophyoidea) and spider mites (Tetranychidae) on wild grasses growing in Wielkopolska region was investigated. Seven species of eriophyoid mites and three of spider mites were found on 24 grass species. Eriophyoid mites infested 38% and spider mites 57% of all examined samples. The most frequent inhabited grass species by eriophyoid mites were Agropyron repens and Lolium perenne, while by spider mites Dactylis glomerata and Bromus mollis.