REPORT OF THE SECRETARY. 137 



eliminating trees affected with dangerous diseases at the time of 

 timber sales. 



Very valuable results have been secured in the control of diseases 

 of forest nursery stock. The leaf blight of young conifers has been 

 shown to be readily controlled by slight modifications of prevailing 

 nursery practice, particularly in connection with irrigation. The 

 damping-off of forest-tree seedlings has been controlled by the use 

 of soil fungicides, particularly by sulphuric acid. The white-pine 

 blister rust has been destroyed wherever found, and the work on this 

 disease has been largely responsible for the passage of the present 

 plant quarantine act, which should prevent its further introduction. 



Cooperation is in effect with 11 States in the investigation and 

 control of the chestnut-tree bark disease, the most destructive of all 

 tree diseases, and the work of checking its progress through methods 

 vorked out by this department is being vigorously prosecuted. 



One important branch of the forest pathological work is the 

 study and control of the diseases of shade and ornamental trees and 

 shrubs. There is a great and growing demand from the general 

 public for information in regard to such diseases. 



DISEASES OF FRUITS. 



The effective control of pear blight, one of the most serious diseases 

 affecting pomaceous fruits, has been accomplished through eradica- 

 tion methods and has resulted in the saving of millions of dollars 

 to pear orchardists on the Pacific coast and in other parts of the 

 country. 



Apple bitter-rot, a disease wdiich has been responsible for immense 

 losses to apple growers, has been shown to be easily and completely 

 controlled by proper spraying with Bordeaux mixture. 



A number of other apple diseases, such as scab, leaf-spot, powdery 

 mildew, and blotch, have also been successfully controlled by spray- 

 ing. Partial control of apple cedar-rust has been accomplished by 

 cutting down the cedars and by spraying. 



With the exception of bitter-rot, it has been found preferable to 

 spray for the early treatments of apple diseases with lime-sulpluir 

 solution, using Bordeaux mixture for the later treatments. This 

 practice has resulted in less russeting of apples from copper poison- 

 ing and has not reduced the effectiveness of the treatment. 



Investigations have been carried on in connection with a number 

 of physiological diseases of fruits, particularl}'^ of the apple, includ- 

 ing apple bitter-pit. a disease producing corky spots in the Ben Davis 

 and York Imperial apples, and tlie Jonathan fniit-spot. In tlie latter 

 the trouble has been remedied by early picking and prompt storage. 



