FIR DISEASES 161 



Control. 



This witches'-broom of fir may be controlled by eradicating 

 all sandwort and chickweed (Alsine and Cerastium) from the 

 immediate vicinity of the firs. 



Reference 



Hartig, R. iEcidium (Peridermium) elatinum. In Text-book of 

 the diseases of trees, pp. 179-182, figs. 109-112. 1894. 



Gray Mou) Twig-Blight 



Caused by Botrytis cinerea Fries 



This disease of the current season's twigs is most important 

 on Douglas fir, although other firs, pine, spruce, larch and hem- 

 lock may be affected. The disease is common in certain lo- 

 calities in Europe and North America, both in nurseries and 

 in the forest. It has been reported as destructive, especially 

 to Douglas fir in nurseries, forest plantings and to some degree 

 on the older trees, in several countries of Europe. In the 

 forests of northwestern United States it occurs on Douglas fir; 

 grand fir, western larch and western hemlock. It has not as- 

 sumed great importance in any area but causes considerable 

 cumulative damage. 



Symptoms. 



The most obvious general symptom of this disease is the 

 withering, curling and dying of young twigs of the season. 

 Seedlings and young trees may be killed. Late in the season 

 black bodies the size of a pin-head are formed on the affected 

 twigs and on the leaves, especially at the base of the season's 

 growth. The twigs of young pine may be dwarfed, the needles 

 remaining short and the twig becoming twisted. Under moist 

 conditions, a more or less luxuriant mycelial growth occurs, 

 forming a gray mold over the affected leaves and twigs. 



M 



