50 Forest Club Annual 



ditions. In this case the injury, to young Scotch Pine resembled 

 the chinook injury in the Black Hills on Yellow Pine, in that 

 the injury was primarily to needles and twigs, and branches 

 were only killed in the most severe cases. However, the kill- 

 ing of Scotch Pine needles was in one way just the reverse 

 of the Black Hills chinook type. At Lincoln the last year's 

 growth in the Scotch Pine was the most susceptible, while in 

 the Black Hills it was the most resistant. The injury to 

 Pinus ponderosa at Lincoln, however, was terminal twig killing, 

 which was entirely different from the chinook type of the pre- 

 ceding winter on the same species in the Black Hills. The 

 superior resistance of Scotch Pine needles formed late in the 

 season over those formed earlier in the same season is of in- 

 terest. Hhe fact that terminal growths of the leaders of 

 White Pine branches were less susceptible than terminal 

 growths of lateral branchlets, is also noteworthy. Just what 

 weather factors caused most of the trouble at Lincoln cannot 

 be said. Anyone who cares to look up possible clues can 

 examine complete weather records taken at the Lincoln sta- 

 tion of the Weather Bureau, only 3 miles from the injured 

 trees. I believe these include constant graphic records of 

 wind velocity, wind direction, temperature, and relative hu- 

 midity. Pressure of other problems will prevent the writer 

 going further into this matter. 



Some winterkilling occurs at the Forest Service nurseries 

 in this District. In general, however, Pinus ponderosa beds 

 require no protection. At Monument, Colorado, I am told that 

 light mulch is needed to prevent winterkilling Douglas Fir. 

 At Halsey, in the sand hills . of western Nebraska, so little 

 winterkilling in the nursery beds has so far occurred that 'at 

 present mulch on the Pinus divaricata, P. sylvestris, P. pon- 

 derosa and P. austriaca beds which are grown there is considered 

 unnecessary. 



Real winterkilling should not be confused with death of 

 nursery stock under heavy mulch, which is probably a para- 

 sitic trouble. In the near future it is expected that a circular 

 will be issued by the Bureau of Plant Industry in which winter- 

 killing and related diseases in coniferous nursery stock will 

 be more fully discussed. Death under heavy snow covering 

 may also be 'a parasitic trouble, and certainly is not caused in 

 the same way as winterkilling of uncovered stock. 



