432 DISEASES OF ECONOMIC PLANTS 



of nearly all species of ash. The winter condition is found 

 upon marsh grass, Spartina. 



The injury is not usually large, but in seasons favorable 

 to the disease defoliation may result. Diseased leaves 

 should be collected and burned. 



Phyllostictose {Phyllostida viridis Ell. & KelL). — Brown 

 spots, 5-10 mm. in diameter, with conspicuous yellow 

 borders and minute black pycnidia, appear upon the leaf- 

 lets. Defoliation may result. 



Leaf spots. — Leaf spots due to several species of fungi 

 are frequently seen, but not in destructive form. Among 

 the causal fungi are : Gloeosporium, Sheer opsis, Septoria. 



BIRCH 



Sapwood rot {Polyporus hetuUnus Fr.). — Several species 

 of birch are affected by this rot, which is of wide distribu- 

 tion in the northern United States. The fungus enters the 

 sapwood from the bark through wounds or through the 

 lenticels, and progresses inward. The yellowish, cracked, 

 fliseased wood crumbles when fully decayed. 



Rust {Melampsora hetulina (Pers.) Tul.). — This is much 

 like the willow rust. See p. 450. 



BUTTERNUT 



Gloeosporiose (Gloeosporium juglandis (Lib.) Mont.). — 

 The affected leaflets bear circular dead spots, indefinitely 

 bordered, and defoliation results. The disease spreads very 

 rapidly throughout the tree, and to other trees. 



CATALPA 



Leaf spot (Pkylhsticta Catalpce Ell. & Mart.). — Affected 

 leaves bear round brown spots, often with a yellow- 



