TBEES AND TIMBER 



449 



causes a stoppage of the water supply to the more distant 

 portions of the leaf, resulting 

 in dead areas. 



Dead twigs should be pruned 

 out, and infected material col- 

 lected and burned. Spraying 

 with Bordeaux mixture may 

 be practiced if the expense is 

 warranted. 



Powdery mildew. See oak. 



BLACK WALNUT 



Anthracnose, Gnomoniose 



{Marsonia juglandis (Lib.) 

 Sacc. of Gnomonia juglandis). 

 — Conspicuous brown spots, 

 2-4 mm. in diameter, appear 

 upon the leaflets, which soon 

 yellow and fall. Upon the 

 lower sides of the leaf spots 

 are small, concentrically ar- 

 ranged, black acervuli. 



The disease has been trouble- 

 some in Delaware, Iowa, Mary- 

 land, and West Virginia. 



WALNUT, ENGLISH 



Pseudomonose, blight (Pseu- 

 domonas juglandis Pierce •) . — 

 Up to the present time this disease has occurred only 



• Pierce, N. B., Bot. Gaz. 31, 273. 

 2a 



Fig. 195. — Walnut twig blighted by 

 bacteria. After R. E. Smith. 



