10 March, 1916.] 



The Walnut. 



155 



Official Record of Rain, Bright District, for the Last Three 

 Months in the Years 1913-1914. 



1913. 

 October 

 November 

 December 



1914. 

 October 

 November 

 December 



This shows that the development of this bacterial organism is 

 influenced by the same atmospheric conditions as largely controls the 

 development and growth of fungus diseases generally. Although preva- 

 lent in the walnut areas of the State, and commonly termed black spot, 

 very few growers know that the actual cause of this walnut disease is 



Fig. 32. — A. Walnut Blight Organism (Pscudonionas juglandis) greatly enlarged. 

 B. A mass of the bacteria in diseased walnut tissue, (After Smith, 

 Bulletin No. 231). 



the workings of a bacterial germ, Bacteriosis of the walnut is a micro- 

 organism, rod shaped, having rounded ends, and occurs as a single rod 

 or often in pairs, and more rarely in chains of several individuals, com- 

 monly four to eight. An American authority gives the measurement of 

 these rods as found in diseased tis.sue from 1.5 to 3.01 microns in 

 length by 0.3 to 0.51 microns in width. A micron is the millionth 

 l)art of a metre, or 1/25400 of an inch. (Plate 32.) 



This blight organism is motile, i.e., capable of spontaneous motion, 

 increasing rapidly in number by elongation and division, or fission. 



"Walnut bacteriosis does not confine its attack solely to the developing 

 nuts. It may occur upon all the tender, new, growing parts of the 

 trees, such as young nuts, branches, and parts of tlie foliage. On the 

 affected parts blackisb-colftured areas, or pronounced lesions (wounds) 



