TREES 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 jnglandis (Lib.) 

 Sacc. of Gnomonia leptostyla 

 (Fries) Ces. & d. Not.).— Con- 

 spicuous 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 arranged, black 

 acervuli. 



The disease has been trouble- 

 some in Delaware, Iowa, 

 Maryland, and West Virginia. 

 WALNUT. ENGLISH 



Pseudomonose, blight (Pseu- 

 domonas jnglandis Pierce^). — 

 Up to the present time this disease has occurred only 



1 Pierce, N. B., Bot. Gaz. 31, 273. 

 2g 



Fig. 195. — Walnut twig blighted by 

 bacteria. After R. E. Smith. 



