GALL-MIDGES (DIPT, CECIDOMYIIDAE) ASSOCIATED WITH POPULUS-TREMULA, P-TREMULOIDES AND THEIR HYBRID (SALICACEAE)

Galls caused by seven species of European cecidomyiids were found on l eaves of Populus tremula, native to Europe, on P. tremuloides, native to North America, and on leaves of their hybrids planted in southern B ohemia. Some galls on hybrids had unusual shapes. Factors influencing the process of establishment of gall midges on new plantings of these trees and their hybrids are discussed. The horizontal and vertical occ urrence of five nail midge species occurring abundantly on P. tremula in the Czech Republic are described. Some gall midge species associate d with P, tremula are abundant in central Europe but they do not cause significant injury to the trees. Prodiplosis mor)isi caused severe in jury to poplars in Canada. European species Contarinia populi occupies a relative small distribution area in central Europe, Harmandia tremu lae extends up to the Ural Mountains, H. cavernosa, spread up to centr al Siberia and Contarinia petioli is broadly distributed from Europe t o the Far East.