THE AMERICAN GRAPE MILDEW. 



(Pero7iospora vUicola, B. & C.) 



BY BYEOX D. IIALSTED, M. S. 



There is probably no cultivated plant that is made the home and means of 

 support of a larger number of parasites, both animal and vegetable, than the 

 grape vine. 



The injury done by the phylloxera and other insects, forms a distinct chapter 

 in the diseases of the grape, and one that must be left for other hands and at 

 some other time. In fact the list of Fungi which thrive upon our vineyards is 

 so long, that for the present paper we are forced to confine our attention largely 

 to a single one, namely: the American Grape Mildew, or Peronospora viticola, 

 B. and 6'., as it is styled in Botany. It is hoped that with the aid of a plate 

 we may be able to make the description of this pest sufficiently plain so that it 

 will not be confounded with any other grape fungus or mistaken for galls or 

 other insect work. 



The grape mildew of which we are to treat is a fungus, we have said. But 

 what is a fungus? It is a member of the group fungi, one of the divisions of 

 those plants which never produce llowers and seeds, and are called crypto- 

 gams ; some of the other orders of which are ferns, mosses, lichens, and 

 seaweeds. Of the group fungi the mushroom and toadstool are among the 

 largest and most familiar members. The moulds which sometimes grow on our 

 bread, cake, and other articles of food arc good examples of those smaller 

 kinds like the species of whicli we are now prei)ared to speak. 



In order to become more thoroughly acquainted with the prevalence of the 

 mildew a list of four questions was made as follows and sent to several of the 

 leading grape growers in various parts of the United States : 



1st. Are you troubled with the grape mildew ; and if so, for how long a time 

 and to what extent? 



2d. About what time does it make its appearance with you; and what are 

 its first manifestations? 



3d. How would you describe the disease? 



4th. Wiiat remedies have you used ; witii the results of each? 



An earnest request was also added for any further information upon the 

 subject. 



