OIDIUM OR POWDERY MILDEW OF THE VINE. 331 



in moist parts of the vineyard near irrigation ditches or in the shade 

 of trees. Very vigorous vines or susceptible varieties in cool seasons 

 also may exceptionally require another sulfuring just before the grapes 

 commence to color or to soften. These late sulfurings, however, are 

 dangerous in the hot districts for reasons already given, and can nearly 

 always be avoided if the earlier treatments are applied properly and in 

 time. 



There are cases where it is advisable even in the interior to give the 

 vines a sulfuring before the blossoming time. If the vines were badly 

 attacked during the previous season there will be an abundance of 

 spores in the vineyard and much injury may be done before the blos- 

 soming time if the spring is warm. In such cases, it is best to give an 

 early sulfuring at the time the vine shoots are about 6 to 8 inches long. 

 For this sulfuring it is very necessary to choose suitable weather. If 

 unfortunately this treatment is followed by rain or continued heavy 

 winds without any intervening warm days, it should be repeated. 



This early sulfuring is very useful also in destroying the mites 

 causing erinose?- a disease which often does considerable damage to the 

 vines before the weather is warm enough for very rapid growth of 

 Oidium. The erinose attacks with particular intensity Mission and 

 Flame Tokay. 



In the coast valleys, Sonoma, Napa, Santa Clara, etc., two sul- 

 furings should always be given ; the first at the time the shoots are 

 from 6 to 8 inches long. This treatment might be omitted in dry, well 

 ventilated situations with resistant varieties, if sulfuring were univer- 

 sally practised throughout the district, but it is at present always safer 

 to apply it. The second sulfuring should be at blossoming time. In 

 dry early summers, except with the most susceptible varieties such as 

 Carignane, a third sulfuring will often be unnecessary. The vine 

 should be carefully watched, however, and, on the first appearance of 

 mildew, sulfur applied again. In bad seasons a fourth sulfuring just 

 before the commencement of ripening may be necessary. By watching 

 the parts of the vineyard which experience has shown to be the most 

 quickly affected, it is always possible to control the disease before it 

 has done any serious damage. 



After the grapes have commenced to ripen, they are almost safe 

 from the attacks of Oidium, but it is a mistake for this reason to allow 

 the fungus to become abundant on the leaves, as it may in warm, moist 

 autumns. Though such a late attack may do little or no damage to the 



1 See Bulletin No. 136, < ' The Erinose of the Vine. 



