OIDIUM OR POWDERY MILDEW OF THE VINE. 329 



110 F., or with varieties particularly susceptible to sulfur fumes, 

 such as Isabella, Othello, and certain other American varieties and 

 hybrids. 



If the earlier sulfurings are done properly, however, it will seldom 

 be necessary to treat the vines in such weather and we may consider 

 that the sulfur which goes on the ground is almost completely wasted. 

 Effects of Sulfur on the Vine, Fruit, and Wine. The effect of 

 sulfur on the vine is in no way injurious except under the conditions 

 already noted. On the contrary, most observers concur in noting im- 

 provement in the health and vigor of the vines after sulfuring irre- 

 spective of the control of mildew. Whether this is due to some stimu- 

 lating action of the sulfur on the foliage or to its action on the plant 

 food in the soil is in doubt. 



The favorable influence of sulfuring the vines, while in blossom, on 

 the setting of the fruit is even more generally recognized. If Oidium 

 is present, this is easily accounted for by the prevention of the action 

 of the fungus on the blossoms. The effect, however, is noticed even 

 when no Oidium exists in the vineyard. The tendency of many vari- 

 eties to " coulure," dropping their blossoms without setting, can be 

 lessened by vigorous sulfuring during the blossoming period. Whether 

 this is due to a stimulation of the floral organs under the action of the 

 .sulfur, to the destruction of unrecognized fungi on the blossoms, or 

 merely to the mechanical action of the current of air produced by the 

 blowers in promoting pollination has never been determined. 



Heavy, late sulfuring may introduce notable quantities of sulfur 

 into the wine. This sulfur is apt, under the influence of the yeast, to 

 give a disagreeable odor of sulfureted hydrogen to the wine. This 

 odor is usually temporary and disappears after a few rackings of the 

 wine. When the sulfuring is done with a suitable machine, however, 

 .so little sulfur is placed upon the grapes that this danger is not to be 

 feared. 



Properly sulfured vines ripen their grapes from 7 to 10 days earlier 

 than those attacked by Oidium. This is probably due to the better 

 health of the vines, which allows the fruit to develop more quickly and 

 more perfectly. 



Proper time and Weather for Sulfuring. The time of day at which 

 the sulfur is applied is of little importance, provided the weather is 

 suitable. It may be applied when the leaves are dry or when they are 

 moist with dew. It is less effective, however, if the leaves are very wet, 

 as the drops of water have a tendency to gather the sulfur into patches 

 -and leave parts of the leaf untreated. 



