150 



GARDEN FOES. 



The I'laigLis can only spread to any extent when the 

 temperature i'S fairly high, and the air contains a consider- 

 able quantity of moisture. In this country, where vines 

 are grown under glass, those conditions most favourable 

 for the development and rapid diffusion of the fungus are 

 constantly present, and great care must be exercised in 

 the matter of ventilation, so as to avoid an undue deposi- 



rOWDEUV MILDEW OF THE Vl.NE. 



tion of moisture on the surface of leaves or fruit; and, 

 furthermore, ventilation must be so effected that the fruit 

 is quite dry before being exposed to sunlight, otherwise 

 rusting of the grapes is apt to occur, a feature bad enough 

 in itself, and in addition greatly favouring the spread of 

 the disease. 



