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Wisconsin State Horticultukal Society. 



can Grapevine Mildew. The true grape disease, the one whicli 

 has proved so disastrous at different times to the vines of Europe 

 and Madeira, is caused by another fungus, to which Berkeley has 

 given the name of Oidium Tuckeri. It is a form of a fungus 

 which had not been recognized in its perfect state, and is supposed 

 to occur to some extent on this side of the waters ; but as many 

 species have this conidial form, and some nearly identical with it, 

 and also growing on the grape, there may be some doubt as to 

 our vines ever being attacked by true 'grape disease of Europe. 

 The Peronospora viticola, the mildew which most interests the grape 

 growers of America, is quite common, appearing on the under 



Fio. 6. Peronospoea viticola. 



surface of the leaves about the first of August, and continuing to 

 flourish until the leaves will nourish it no longer. It can be most 

 easily seen on the smooth leaves of the Viiis cordtfoUa, having the 

 appearance of small, frost-like spots, which rapidly spread and 

 soon cover the whole leaf, frequently extending down the petiole 

 to the stem. This fungus, like the potato rot and other closely- 



