346 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



is necessary to treat for another vine disease which cannot be con- 

 trolled by sulfur at the same time. In Europe, where spraying with 

 copper solutions is necessary to protect the vines from Peronospora, 

 Black Rot, and Botrytis, various sprays have been tried with the object 

 of controlling the Oidium at the same time. These sprays are princi- 

 pally liquids containing Bordeaux mixture, copper sulfate, or sulfoste- 

 atite together with "wetable" sulfur. There is considerable uncer- 

 tainty as to the success of these combinations, and as the diseases they 

 are intended to reach do not exist in California they are of little in- 

 terest to us. 



The other case is where sulfur has been found ineffective or too 

 slow in its action. This seems to be the case in the Eastern States, and 

 may be in certain parts of the coast region of California or perhaps 

 exceptionally in other regions in abnormal years. 



Liquid Sprays. Dry sulfur to be effective requires warm weather. 

 If the weather is cool its action is slow or nil. Certain sprays act im- 

 mediately on the Oidium whatever the temperature. It should be re- 

 membered, however, that the Oidium grows very slowly or not at all 

 below temperatures at which sulfur is effective. Cases, however, may 

 arise where, through neglect of proper sulfuring, the vines may be 

 badly attacked by mildew, and owing to the coolness of the weather 

 when the trouble is first perceived sulfur may act too slowly. In such 

 cases it may be advisable to use a quick acting spray. 



Such a condition might occur in a cool late spring. 



Another case in which a spray may be useful is where the vines 

 have been very badly affected the previous autumn and the canes are 

 covered with winter spores and perhaps hibernating mycelium ready 

 to infect the new shoots on the first warm day. A spraying just as the 

 buds swell might be of help in such a case. 1 



Spraying in the summer should never be necessary, as the heat is 

 sufficient to cause the sulfur to act quickly. It has been suggested that 

 late sulfuring is inadvisable because it may cause spotting of the 

 grapes. If the grapes have not commenced to ripen this will not occur 

 if the sulfur is applied properly, and if they have commenced to ripen 

 they are safe from the disease, and sulfuring to protect the vines should 

 be deferred until the grapes are gathered. 



No sprays, however, do the work as thoroughly as sulfur. A spray 

 only kills the fungus which it actually touches, and the most perfect 

 spraying possible will leave some parts of the vine untouched. Where 



1 Tests of winter spraying by Pacottet and Eavaz in France gave no favorable 

 results. 



