16 BULLETIN 120, TJ. S. DEPARTMENT OF AGRICULTURE. 



This operation of washing the precipitate should be repeated until 

 the water poured off no longer shows the yellow lime-sulphur tinge. 

 Probably three or more such washings will be required, depending 

 upon how careful the operator has been in using only a slight excess 

 of lime-sulphur solution. 



It is evident that the preparation of this stock supply should be 

 commenced two or three days before the spraying is to be done, but 

 when once prepared it may be kept indefinitely. If care is used in 

 weighing out each lot of iron sulphate and if the lime-sulphur solu- 

 tion used is accurately measured there will be no trouble in making 

 up the stock supplies rapidly after the first two or three batches 

 have been prepared, and it will be remembered that each batch is 

 sufficient for making 500 gallons of spray mixture. In order to keep 

 a supply of the stock mixture on hand, several batches should be 

 prepared before the spraying commences, and as rapidly as a barrel 

 is emptied the preparation of a new batch should be started. Iron 

 sulphate is comparatively cheap, and the entire cost of materials for 

 preparing 100 gallons of the mildew spray, when diluted according 

 to the recommendations given in this bulletin, should not exceed 15 

 or 20 cents. 



When the washing has been completed, the stock barrel should be 

 filled with water to exactly 50 gallons. The material is now ready 

 for use as directed under " General formula for the spray mixture," 

 on page 17, but care should be taken to stir the contents of the barrel 

 thoroughly each time before any of the mixture is taken out. 



IMPORTANCE OF EARLY SPRAYING. 



Attention has been called to the fact that the apple foliage is sub- 

 ject to mildew attack shortly after it begins to come out in the spring. 

 The serious fruit dropping that may result from delaying the first 

 application until after the fruit is an inch or more in diameter has 

 been discussed, and attention has been called to the possibility of 

 developing sulphur immunity or resistance to injurious sulphur 

 effects by beginning the spraying early and repeating it at intervals 

 of two to three weeks. Also, it has been stated that these sulphur 

 sprays have a distinct stimulating effect on foliage growth and that 

 the mildew is more readily controlled on vigorously growing trees. 

 Thus there are a number of reasons for making the first spray appli- 

 cation early in the season, namely, to protect the very early foliage 

 from mildew, to develop immunity to sulphur injury and thus avoid 

 serious fruit dropping later in the season, and to bring about sul- 

 phur stimulation, thus inducing a vigorous early growth of foliage. 

 Furthermore, it has been found that precipitated sulphur acts as a 

 restrainer of the arsenical foliage injury that in the Pajaro Valley 



