220 MANUAL OF FRUIT DISEASES 



surface of the diseased portion is smoky in color. The lesions 

 are roundish or angular, and measure from one-sixteenth to 

 one-eighth of an inch in diameter. Little attention has been 

 given to the life-history of the pathogen e. 



The disease may be controlled by the schedule advised for 

 the Mycosphserella leaf-spot (see page 205). 



REFERENCES ON ANGULAR LEAF-SPOT 



Pammel, L. H. Spot diseases of currants and gooseberries. Iowa 



Agr. Exp. Sta. Bui. 13 : 67-70. 1891. 

 Pammel, L. H. Treatment of currants and cherries to prevent spot 



diseases. Experiments with currant spot diseases. Iowa Agr. 



Exp. Sta. Bui. 30 : 289-291. 1895. 



AMERICAN POWDERY-MILDEW 

 Caused by Sphcerotheca mors-uvce (Schw.) B. and C. 



This is believed to be primarily a gooseberry disease both in 

 Europe and in America. It may, however, cause considerable 

 injury to currant bushes, as was noted in July, 1915, on black 

 currants in a New York State nursery. The disease was then 

 found affecting the varieties Champion, Naples and Saunders, 

 while red currants near by were resistant. The trouble has 

 also been reported from Ohio, Nebraska, Washington and 

 California. 



The affected leaves and berries are covered with a brownish 

 felt-like growth. 



Although the causal fungus, Sphoerotheca mors-uvce, is mor- 

 phologically the same as that causing gooseberry-mildew, yet 

 limited observations indicate that the pathogene on the currant 

 is so specialized that it refuses to infect even the most sus- 

 ceptible varieties of gooseberries. Conversely, the fungus, even 

 when abundant on gooseberries, is rarely found on currants 

 growing in close proximity. (See Gooseberry, page 222.) 



