WALNUT CULTURE IN CALIFORNIA. 



WALNUT BLIGHT. 



By RALPH E. SMITH. 

 Assisted by CLAYTON O. SMITH and HENRY J. RAMSEY. 



The present bulletin represents the results of the most extensive, and, 

 perhaps, the most important investigation undertaken by the depart- 

 ment of plant pathology since its foundation. When the writer first 

 came to California in 1903, one of the most conspicuous and most seri- 

 ous plant diseases then prevalent in the State was the so-called walnut 

 blight. The disease, while comparatively a new one at that time, had 

 reached all the important walnut-growing districts and was reputed to 

 have been the cause of a diminution of at least one half in the walnut 

 crop of the State. The trouble had been under investigation for some 

 little time by Professor Newton B. Pierce, then of the United States 

 Department of Agriculture, who had succeeded in definitely establish- 

 ing its cause and had undertaken considerable work along the line of 

 treatment for its suppression, and also that of developing varieties of 

 the walnut which might be immune to this disease. Professor Pierce, 

 however, was burdened with much other work, which prevented his giv- 

 ing to walnut blight the amount of attention which the walnut grow- 

 ers felt that the subject justified ; indeed, the importance of the matter, 

 owing to the extensive ravages of the disease, seemed to justify every 

 possible effort toward finding means for reducing the great losses 

 occasioned by this trouble. The walnut growers' associations had, 

 therefore, offered a standing reward of twenty thousand dollars for 

 a feasible remedy for the blight, and were eager to demand all possible 

 assistance in solving this problem. The legislature of 1905 made an 

 appropriation of four thousand dollars to the Regents of the University 

 of California, directing them to cause to be prosecuted investigations 

 looking for a remedy for the walnut blight, and under this appropria- 

 tion the present work was started. 



In the spring of 1905 a laboratory was established in the city of 

 Whittier. Los Angeles County, primarily for the study of walnut 

 blight. This laboratory was placed in charge of Mr. Albert M. West, 

 an experienced bacteriologist, who, under the direction of the writer, 

 commenced the investigations which are reported in this bulletin. The 

 work was largely contributed to in later years by Messrs. Clayton 0. 

 Smith and Henry J. Ramsey, the latter working particularly upon the 

 pomological side of the investigation, while Mr. Smith's work has been 



