BULLETIN 231] WALNUT CULTURE IN CALIFORNIA. 321 



ment Station nursery. The disease has never been found on the straight 

 California black or on Royal hybrids, although it can be produced 

 artificially by puncture inoculation on various species of Juglans. 

 In one instance a case of blight infection was observed in the nursery 

 on the leaves of California black seedlings near a badly diseased 

 branch, caused by artificial puncture inoculations. It is probable that 

 these leaves were infected from the disease on the branches. 



Popular Name of Disease. Newton B. Pierce first described this 

 disease as walnut bacteriosis, but locally it is also known as walnut 

 blight. In this paper, however, the more suggestive term Bacteriosis 

 will be used for the most part. 



Geographical Distribution. It is not definitely known just how 

 widely spread this disease may be. In the United States it is found 

 more or less scattered over California, some localities being more 

 severely infected than others, due either to climatic conditions or to 

 the disease not yet having obtained a foothold. California has had 

 the disease for a quarter of a century, and now it is beginning to show 

 itself in Oregon. 1 The disease has also been reported from Texas, 2 

 and is said there to attack nearly every year all the native nuts of the 

 walnut family. This Texas trouble has not yet been, with certainty, 

 identified as the same disease as the walnut bacteriosis in California. 

 Diseased walnut leaves have been received from at least one point about 

 midway down the Pacific coast of Mexico. From this diseased material 

 typical walnut blight cultures were grown. The walnut trees were, 

 however, imported from California. This disease will probably appear 

 wherever the English walnut can be commercially grown in the United 

 States, and the only reason that it is of no economic importance in the 

 Southern and Eastern States is because the walnut industry has not 

 yet been developed there. In foreign countries the disease has been 

 reported from New Zealand.* California walnut growers who have 

 visited France report having seen our trouble on French walnut trees. 

 Too much reliance cannot, however, be placed on these observations 

 because of a fungus disease (Marsonia juglandis) that produces quite 

 a similar appearance to that of our walnut blight. (See description of 

 Marsonia juglandis, page 325. The testimony of these growers is, 

 however, strengthened by certain observations of our own. In 1907 

 walnut scions were imported from France, and among these were several 

 that had what appeared to be typical walnut blight lesions. Cultures 



1 C. I. Lewis, Oregon Experiment Station, Bui. No. 92, p. 19. 



2 G. E. Schattenberg, Texas Department of Agriculture, Bui. No. 2, pp. 42-43. 



*W. A. Boucher, New Zealand Department of Agriculture, Report 1900, pp. 334-335. 



T. W. Kink, New Zealand Department of Agriculture, Report 1907, p. 167. 



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