136 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



Much has been done to improve farm practices there and to put beet 

 culture on a permanent and rational basis. In conclusion, it is safe 

 to say that the beet-sugar industry is now one of tlie mainstays and 

 chief supports of agriculture under irrigation in this country. 



PROGRESS IN PLANT PHYSIOIX)GY AND PATHOLOGY. 



As indicated at the outset of this statement reijarding: the work 

 of the Bureau of Plant Industry, one of the fundamental lines of 

 work which the present Secretary had in mind was a study of the 

 diseases of crops, with a view to outlining specific remedies for the 

 same. Much progress has been made in this work not only so far as 

 the department is concerned but throughout the country as a whole. 

 The plant pathological work of the department is now on a firm 

 foundation. Our leading pathologists have developed lines of work 

 which have been epoch making in their nature. 



PROBLEMS IN PLANT PATHOLOGY. 



The cause of the crown-gall of plants has been determined, and it 

 has been discovered that this disease resembles animal cancer in its 

 manner of growth and is due to bacteria lodged inside certain of the 

 proliferating cells. 



It has been proved that infection of Stewart's bacterial disease of 

 sweet corn is produced by means of seed corn ; that the black rot of 

 crucifers, the brown rot of potatoes, the wilt of cucurbits, and other 

 bacterial diseases are distributed by insects and slugs; that tobacco 

 wilt is spread by nematodes; that bacterial infection can take place 

 through stomata in the absence of wounds, as in the case of the black 

 spot of plum, a disease of sweet corn and broom corn, and other 

 plant diseases; that acid canes are resistant to the bacterial disease 

 of sugar cane ; that many bacteria, including Bacillus typhosus^ are 

 readily destroyed by freezing; that the Granville tobacco wilt is 

 identical with the bacterial brown rot of potato, eggplant, and tomato, 

 and hence these plants should not be used in rotation. 



The cause and remedy of the olive tubercle disease, coconut bud 

 rot, bacterial mulberry blight, and a new knot disease of citrus 

 trees have been discovered. 



It has been shown that the cause of a large part of potato rot is 

 due to Bacillus fhytoyhthonis^ and that the rot is arrested in tubers 

 stored below 8° C. 



FOREST PATHOLOGY. 



A general pathological survey of the National Forests has been 

 made as a preliminary to active investigational work. Extensive 

 experiments have been inaugurated for controlling forest diseases 

 by the improvement of forest hygiene, chiefly by the method of 



