CHAPTER XVII 



ELM DISEASES 



Fig. 21, — Leaf-spot of elm. 



152 



The elms (Ulmus) are 

 common forest and orna- 

 mental trees east of the 

 Rocky Moimtains. They 

 are exceptionally free from 

 specific diseases caused 

 by parasites. Wound-rots 

 and slime-flux are common 

 in the crotches of the large 

 limbs. Chaining is often 

 necessary to prevent split- 

 ting at the crotches. 



Leaf-Spot 



Caused by Gnomonia idmea 

 (Sace.) Thiim. 



This is the most com- 

 mon of the leaf-spot dis- 

 eases of elm. In wet 

 seasons, the spots become 

 so abundant that defolia- 

 tion results. The fungus 

 causing this disease usu- 

 ally occurs abundantly 



