18 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 



(Schrad.) Chev. It later became apparent that this species was sus- 

 ceptible to a variety of other diseases, among them the above-mentioned 

 C. ribicola 1 Armillaria mellea (Wahl.), and Leptostroma strobicolla 

 Hil. Injurious animals increased the damage. For these reasons cul- 

 tivation of white pine is now limited. 



It is worthy of mention that Cronartiuin ribicola occurs individually 

 even on the native Pinus cembra in the High Tatra Mountains. Jack 

 pine, Pinus banksiana, was cultivated toward the end of the 19th and 

 the beginning of the 20th century because of its resistance to pine needle 

 cast. Low growth rate of this species at older ages caused a return to 

 the use of Scotch pine, Pinus sylvestris, despite its susceptibility to 

 needle cast. 



European larch, Larix decidua. suffers severely from Dasyscyplxa 

 willkommii (Hart.) Rehm. and more resistant races are being sought. 

 The good qualities of the Sudeten and Tatra larch may be stressed 

 rather than trying to use the very susceptible European larch. It is 

 also planned to take advantage of the resistance of Larix leptolepis 

 in hybridization work. Larch in forest nurseries is attacked by the 

 needle cast caused by Meria laricis Vuill. Experiments should be 

 carried out to test the resistance of various provenances. 



Douglas-fir is an especially important forest tree species. 

 Rhabdocline pseudotsugae Sydow appeared in the CSSR for the first 

 time in 1938 and is spreading in the existant forest stands of this 

 valuable tree species. Successive attacks on Douglas-fir over a period 

 of several years leads to defoliation and, here and there, to the death 

 of trees. The attacks are quite irregular. This disease has not re- 

 duced the popularity of Douglas-fir even though Rhabdocline has 

 spread over large areas in various regions of the Czechoslovak 

 Socialist Republic. 



Adelopus gaumanni Rohde has not yet been recorded in the CSSR, 

 though it is common in neighboring states (German Democratic 

 Republic, etc.). But Douglas-fir is attacked by the foreign aphid 

 Gilletteella cooleyi Gill. In addition, Douglas-fir suffers like other 

 tree species from attacks by the honey fungus, Armillaria mellea. 



Pinus austriaca is planted artificially on lime and extreme sites. 

 It is more resistant to Lophodermium pinastri but more susceptible 

 to Cenangium abietis (Pers.) Duby, which has spread in our country 

 notably since 1959. It is also more susceptible to Naemacyclus 

 niveus Pers. 



Broadleaved tree species are represented notably by Quercus rubra. 

 No important diseases are recorded. 



Foresters are worried by diseases of poplars grown in pure stands 

 after World War II, and mainly from the year 1955. Our native 

 poplar, Populus nigra f. typica Schneider, suffers heavily from 

 Chondroplea populea, brown spot disease, and other diseases. Im- 

 ported poplars are not immune, but here and there Populus monilifera 

 and Euroamerican poplars suffer less than the native ones. 



Hybrids used in forestry and outside the forest, such as Populus 

 robusta. P. regenerata, and P. berolinensis. suffer by brown spotting 

 and Chondroplea populea. 



Pseudomonas rimaefaciens and Nectria do not occur as frequently 

 as in western Europe and other parts of central Europe. Venturia 

 populina (Vuill.) Fabr. attacked the poplar, Populus berolinensis. 

 in one locality. It is not seriously harmful in other places. 



