154 Journal of Agriculture, Victoria. [10 March, 1916. 



THE WALNUT. 



(Continued from page 747, Vol. XTIT.) 



C. F. Cole, Orchard Supervisor. 



DISEASES (concluded). 



Bacteriosis or Walnut Blight. 



Of all known diseases attacking tlie developing nuts of the walnut, 

 bacteriosis is the worst that the grower has to contend with. The 

 loss caused by this bacterial trouble is considerable, and has been 

 mentioned in former articles (vide Journal of Agriculture, August, 

 1914, p. 460). 



It is not definitely known how long this disease has been in Victoria. 

 Mr. C. C. Brittlebank, Vegetable Pathologist to the Victorian Depart- 

 ment of Agriculture, states that he saw walnut trees growing upon a 

 farm in the year 1888 attacked. Mr, J. Farrell, Supervisor of Orchards, 

 submitted in November, 1906, diseased walnuts from the Ardmona 

 district to Mr. D. McAlpine, the Government Vegetable Pathologist, 

 and he diagnosed the trouble as walnut bacteriosis. Erom inquiries 

 made, several growers in the Bright and adjacent districts state that 

 they have known the walnuts to be attacked from twelve to twenty years 

 ago by a disease which they commonly termed black spot. There is 

 no doubt that this black spot of twenty years ago is the bacterial disease 

 of to-day. Up to the present in Victoria there is no record of the 

 fungus disease (marsonia juglandis) appearing. This produces a 

 similar condition to that of walnut bacteriosis. 



From personal observations and the perusal of scientific works deal- 

 ing with this disease, it is found to be more prevalent and virulent in 

 localities where the weather conditions are moist and humid during 

 the spring and early summer than in districts where such weather 

 conditions do not prevail. 



In Victoria the greatest quantity of walnuts is produced from trees 

 growing in districts having a good annual rainfall and subject to moist 

 atmospheric conditions in late spring. Therefore, the walnut crop is 

 partly looked upon as a chance one, owing to the risk of attack by this 

 bacterial organism. 



During the month of November, 1913, in the Bright and adjacent 

 districts the walnut crop looked promising until moist and humid con- 

 ditions set in. By the end of the month the greater percentage of the 

 developing nuts was attacked or destroyed by bacteriosis. 



The following spring and early summer of season 1914 was one of 

 the driest upon record in these districts. The walnut crop was almost 

 entirely free from attack. 



Trees that lost fully 75 per cent, of the crop through this trouble 

 in the spring of 1913 were practically free from attack in the dry 

 season of 1914. 



