382 Diseases of Economic Plants 



ASPEN. See poplar. 



BIRCH 



Sapwood-rot ''*' {Polyporus betulinus Fr.). — Several 

 species of birch are affected by this rot, which is of wide 

 distribution in the northern United States. The fungus en- 

 ters the sapwood from the bark through wounds or through 

 the lenticels, and progresses inward. When completely de- 

 cayed the yellowish, cracked, diseased wood crumbles. 



Rust (Melampsoridimn betulince (Schm.) Arth.). — This is 

 much like the willow rust. See p. 405. 



BUCKEYE. See p. 390. 



BUTTERNUT 



Anthracnose {Gnomon ia lepfostyla (Fr.) C. & de Not. 

 Marssonina). — The affected leaflets bear circular, dead, 

 indefinitely bordered spots. The disease spreads very 

 rapidly throughout the tree, and to other trees. Defoliation 

 results. 



CATALPA 



Leaf-spot {Phylloslicta catalpw E. & M.). — Affected 

 leaves bear round, brown spots, often with a yellowish 

 gray border. The spots, from 3-6 nmi. in diameter, often 

 coalesce to form large blotches which are fragile, sometimes 

 dropping from the leaf. Young leaves develop poorly and 

 are deformed, while severe infection may cause complete 

 defoliation of the tree. 



Soft heart-rot ^"^ (Polyporus versicolor Fr.). — The wood 

 at the center of the tree is discolored and disintegrated, 

 eventually becoming straw-colored and soft. The sporo- 

 phores appear near the wound which afforded entrance. 

 They are sessile, grouped, soft, hairy above with alternate 

 bands of light and dark color. When old, they are tough 

 with edges curled in. See also p. 374. 



