REPORT OF THE SOCIETY 71 



exceptional difficulty in eradicating the Blister Rust from the isolated areas 

 mentioned, but in the case of the main district containing over 300 sq. miles 

 of territory, the problem promises to be extremely hard to solve. Not only 

 are there thousands of small and large currant plantations throughout 

 this Niagara region, thus permitting the rust when once started on currants 

 to sweep over miles of country, but there are as well immense numbers of 

 half -grown and seedling pines scattered about the whole section, all ex- 

 posed each summer to wholesale infection. It would be almost miraculous 

 if there are not now established thousands of pine infections each capable 

 of starting an epidemic of the currant rust. 



The method of fighting this disease which has been heretofore used 

 consists of careful surveys to locate the infected pine or pines, and the im- 

 mediate destruction of these when found. In isolated areas where either 

 pines or currants are few this method can be depended on to give results, 

 especially when it can be continued year after year without much danger 

 of the spread of infection because of the fewness of either host. In the case 

 under consideration, however, the inspection of the immense number of trees 

 in the affected district would be a stupendous task, and even with the most 

 careful inspection the location of more than 90% of the blister cankers would 

 be a virtual impossibility. If currants were scarce and far from each other 

 perhaps the disease could be reduced in successive years in this way and 

 finally eliminated, but the presence of so many currant plantations in close 

 proximity to each other allows the 10% of cankers remaining to start just 

 as much rust as if the whole lot were left. 



Spraying the currants has suggested itself as a means of fighting this 

 disease. We have given this phase of the subject some attention during the 

 recent summer, and have experimented with two fields in the affected 

 district. One of these was sprayed with Bordeaux mixture and the other 

 with soluble sulphur, both at intervals of two weeks, throughout the sus- 

 ceptible part of the season. It was realized that the spray would have to 

 be applied to the under sides of the leaves, and though this was done as 

 thoroughly as possible in our work, it must be admitted that it takes so 

 much time and care that effective spraying of this kind would be almost 

 out of the question in a commercial way. Owing to frequent rains during 

 the summer we did not get the best results from our work, but even allow- 

 ing for this we are certain that though the amount of the rust can be greatly 

 reduced by spraying, it cannot be controlled sufficiently to prevent the 

 spread of infection. Consequently whatever value spraying methods 

 may have as a means of protecting individual plantations, they are likely 

 to be of little use in combatting the disease as a national pest. 



