2 BULLETIN 611, U, S. DEPARTMENT OF AGRICULTURE. 



cializing in the growing of young trees for general planting. These 

 facts, together with the increasing volume of correspondence re- 

 ceived by the Department of Agriculture relative to walnut diseases 

 and the known occurrence of the walnut blight, or bacteriosis, in the 

 eastern United States, make it desirable to publish at this time a 

 resume of the history of this disease and its present status in the 

 section specified, to the end that difficulties and disappointments 

 may be avoided. 



Commercial walnut growing in the United States may be said to 

 have had its origin on the Pacific coast. At present the principal 

 production of Persian walnuts in this country is from a few counties 

 in southern California, although within recent years there has 

 been extensive planting in the San Joaquin Valley, the Sacra- 

 mento Valley and adjacent valleys of northern California, and in 

 the Willamette Valley of western Oregon. To a considerable extent 

 this walnut is now being planted by amateurs and experimenters in 

 other States, especially Arizona and New Mexico. As a result of 

 this situation, systematic studies of the species and its varieties, its 

 cultural requirements, diseases, and insect pests have largely been 

 confined to the West, and except as analogies can be drawn there is 

 little in agricultural literature that will be of assistance to a prospec- 

 tive grower in the eastern United States. 



During the seasons of 1910, 1911, and 1914 specimens of diseased 

 nuts were received by the Bureau of Plant Industry from points in 

 Maryland, Louisiana, Pennsylvania, Virginia, and Delaware and 

 determined by Mr. M. B. Waite, Pathologist in charge of the Office 

 of Fruit-Disease Investigations, to be affected with the so-called 

 walnut blight, or bacteriosis. During the summer of 1916 an effort 

 was made by the writer to determine the extent of the occur- 

 rence and the seriousness of this trouble in the eastern United 

 States, as it appeared to be the most serious disease with which the 

 industry now has to contend in this part of the country. Blighted 

 nuts were found at practically all points at which bearing walnut 

 trees were examined, and reports from other sections indicate that 

 the presence of this disease is more or less general in the entire 

 eastern district. 



HISTORY OF WALNUT BLIGHT. 



In 1901 Pierce l reported a walnut disease due to a bacterium which 

 had at that time become established in the seedling orchards of 

 southern California. He stated that it was highly pathogenic on 

 young nuts, leaves, and tender twigs and frequently caused serious 



1 Pierce, N. B. Walnut bacteriosis. In Bot. Gaz., y. 31, ao. 4, p. 272-2 1 :>. 1901, 



