134 DISEASES OF ECONOMIC PLANTS 



Pustular spot (Helminthosporium carpophilum L6v.)- — 

 Peaches with this disease are described by Selby '■ as 

 " Badly disfigured, having numerous pimply red spots with 

 light brown centers." The peach, in an earlier condition of 

 the disease, shows small rusty brown spots upon its upper 

 side. These spots increase in size and develop light brown 

 centers, 1-2 mm. in diameter. Upon yellow varieties the 

 pustule is commonly lacking, there being but a light brown 

 center with a red border. 



As the fungus which causes this spot rests purely upon 

 the surface its development may be prevented by spraying. 

 Selby''' reduced the injury from 16 per cent to 1 per cent by 

 three appUcations of the Bordeaux mixture. 



Rust (Puccinia Pruni-spinosoe Pers.). — A true rust exists 

 parasitically upon the peach and its relatives, the plum 

 and cherry. While more common upon the plum, it very 

 frequently does damage to the peach, in some cases being so 

 serious as to cause almost complete defohation. The alter- 

 nate stage is not uncommon upon the hepatica in the spring. 



This malady will be recognized by the presence .pf small, 

 round, dusty sori on the lower surface of the leaves and on 

 the young shoots, while in the immediate region of these 

 spore-bearing pustules the leaf, seen from above, often 

 presents a reddish or reddish yellow color. 



Reliance must be placed upon a cleansing spray such as 

 is recommended for the peach curl, to lessen the effect of the 

 attack of the rust. 



Stem blight, phomose {Phoma Persicce Sacc). — A fungus 

 on the bark which fructifies in minute pustules sometimes 



' Solby, A. D., Ohio Agr. Ex. Sta. Bui. 92. 

 ' Selby, A. D., Ohio Agr. Exp. Sta. Bui. 92. 



