18 BULLETIN 44, U. S. DEPARTMENT OF AGRICULTURE. 



but at length gradually become yellow and die. Scotch pine, Rocky 

 Mountain yellow pine, white fir (Abies concolor (Gord.) Parry), 

 Douglas fir, and Norway spruce have been found affected, the latter 

 most seriously. A very similar trouble is known in Germany under 

 the name " Einschniirungskrankheit." It is figured by Tubeuf. 1 

 Various coniferous and broad-leaved species are affected, beech, fir, 

 and spruce being most prominently mentioned. In Germany Pesta- 

 lozzia hartigii Tub. is found on the constrictions and is considered to 

 be the cause of the disease, The causal relation has not been proved 

 by inoculation, despite extensive experiments by Fischer. 2 Of the 

 few cases of disease observed by the writer the fungus has been found 

 fruiting on the lesions in a single case on Rocky Mountain yellow 

 pine from New Mexico. In this case the bark had been dead so long 

 that it had become loose. While the stem girdle in this country may 

 be due to Pestalozzia hartigii, proof is lacking. 



The important practical facts are that the disease does not often 

 do serious damage, and that the only method of combating it which 

 can be suggested is to destroy all diseased material. All girdled 

 trees with bark killed entirely around the stem are certain to die 

 and should be pulled out and burned at once without waiting for 

 them to turn yellow. 



MULCH INJURY. 



In nurseries where beds are covered with a mulch during the winter 

 to prevent heaving or winterkilling, heavy losses sometimes occur 

 while the mulch is on the beds or just after it is taken off. While 

 mulch injury usually occurs during the winter it is an entirely differ- 

 ent thing from the winterkilling in unmulched beds. The general 

 experience of nurserymen has been that the disease was worst where 

 the mulch was heaviest, or where it was composed of fine material 

 which packed down into a close covering. While the injury is the 

 result of the use of mulch, the immediate cause of death is unknown. 

 While physical factors may be entirely responsible, it is quite likely 

 that death is due to some needle parasite whose work is favored by the 

 conditions which prevail in mulched beds. What is very likely the 

 same trouble occurs occasionally under a light mulch, or even under 

 no mulch at all, when there is heavy or very late snow. 



In two cases the writer has had opportunity to examine injured 

 white-pine and Douglas-fir seedlings shortly after the mulch was re- 

 moved. In both bases the roots were still healthy despite the death 

 of the needles and in many plants of the upper parts of the stems. 



1 Tubeuf, Karl von. Diseases of Plants Induced by Oryptogamic Parasites. English 

 edition by W. (J. Smith. London, New York, and Bombay, 1807, p. 492. 



- Fischer, C. E. C. Note on the biology of PeHtaloezia hartigii, Tubeuf. Journal of 

 Economic Biology, v. 4, No. 3, p. 72-77, pi. 7, 1009. 



