278 PROTECTION AGAINST TREE DISEASES 



Fungi causing heart-rots can be controlled in the timber 

 crops succeeding the present one by the methods outlined 

 below: 



(a) Use of a rotation sufficiently short so that the heart-rots 

 do not have the opportunity to destroy more than a small 

 percentage of the timber. 



(b) Prevention of infection of the new crops. 13 This is 

 likely to require: 



1. Disposal or treatment of the infected slash in such a 

 manner as to prevent the production of sporophores. (See 

 page 235.) Slash can be treated either by the use of fire or 

 methods which will insure its drying out and thus check 

 development of the fungi. 14 



2. Felling of all standing infected trees and treatment as 

 given under i. 



3. The retention of thrifty trees free from infection, if a 

 portion of the old stand is left for seeding purposes. 



The white pine blister rust, 15 cronartium Ribicola, intro- 

 duced from Europe previous to 1909, has threatened within 

 the last ten years to develop into an epidemic similar, though 

 less rapid in its spread, to the chestnut blight. The methods 

 of control 16 consist in removing all species of ribes, one of the 

 hosts of the disease, and thus restricting its spread. The 

 cost per acre of eradicating ribes 17 averages less than $0.54 

 per acre and will, as methods of work improve and are 

 standardized, be lowered appreciably. 



Re-eradication every five to ten years appears to be neces- 

 sary but at costs lower than that of the first eradication. 

 Eventually eradication of ribes must be considered a regular 

 operation in growing eastern white pine and be pursued sys- 

 tematically. While termed " eradication " the work in reality 

 reduces the quantity of ribes in a given area, but should not 

 be expected to secure absolute eradication. 



