ii8 DISEASES OF THE SWEET PEA 



POWDERY MILDEW 



Microsphcera alni (Waller) Salm. 



The sweet pea mildew was described by 

 Massee ^ as being prevalent in England. 

 Erisiphe polygoni was thought to be the 

 cause both of the sweet pea and the garden 

 pea mildew. In the United States, Pro- 

 fessor Stewart ^ was the first to record the 

 finding of powdery mildew on sweet peas 

 in the United States. However, Stewart 

 did not find the perithecial stage which 

 would help in the determining of the 

 fungus. 



Powdery mildew is a very prevalent dis- 

 ease on greenhouse sweet peas, although 

 it is also very common on out-of-door 

 plants. The fungus which causes mildew 



^Massee, George, Fungoid diseases of the sweet pea, 

 Sweet Pea Annual: 20-21, 1906, London. 



* Stewart, F. C, Notes on New York plant diseases. 

 New York (Geneva) Agr. Expt. Station BuL 328:394, 

 1910. 



