47G DISEASES OF ECONOMIC PLANTS 



masses. Later in the season the color of the son changes 

 to brick red. 



Affected branches should be promptly burned, and all 

 infective material should be burned in the autumn. If 

 the disease reappears, the whole plant should be dug up 

 and burned. In beds where the disease has occurred, a 

 dormant spray should be applied in early spring. 



Rust {Phragmidium speciosum Fi.). — Though much like 

 the last, this disease is limited to the stems, rarely petioles, 

 in its attack. The sori are irregular and black. Since 

 the causal fungus is perennial in the stems, excision and 

 burning are to be practiced. 



Glcesporiose, anthracnose {Gloeosporium Rosm Halst.). — 

 This anthracnose is very similar to that of the raspberry. 

 The diseased canes, bearing small, pale leaves, die from the 

 tip backward for 2-3 dm., and red acervuli appear upon them 

 after death. Often the canes become completely defohated. 



Affected plants should be sprayed with Bordeaux mix- 

 ture or ammoniacal copper carbonate. 



Sphaerellose (Sphcerella rosigena Ell. & Ev.).^ — The 

 leaves are marked with gray, irregular, indefinite blotches 

 which bear minute black perithecia in their centers. 



Leaf spot, cercosporose {Cercospora rosoncola Pass.). — 

 Circular gray spots bordered with dark purple but with- 

 out pycnidia are present. 



Downy mildew {Peronospora sparsa Berk.). — This 

 mildew is kin to that of the grape. Its spots are indefinite, 

 and the characteristic downy white to purple coating 

 is noted upon the lower surfaces of the leaves. It is not 

 common in America. 



Crown gall. See peach. 



