PESTS OF THE HOP CROP. 153 



reduced to a finely pulverized state, by hand or machin- 

 ery — acts better than that form known as "flowers of 

 sulphur," obtained by condensation of its vapor or by 

 precipitation processes. In any case, the substance 

 acts in two ways (i) as a fungicide — that is, a definite 

 destroyer of the mold; and (2) as a protection against 

 further attacks and spreading, as spores will not ger- 

 minate upon a sulphured leaf. 



It is chiefly as a protector that sulphur is so bene- 

 ficial, and on this account every endeavor should be 

 made to distribute it upon the youngest growth. As 

 a direct fungicide, it possesses little effect, and even for 

 this small benefit it must be repeated frequently where 

 mold is bad. The best results with sulphur are ob- 

 served wdien the temperature is above 78 degrees F., 

 and it is, therefore, usually applied with success on 

 clear, bright, hot days, usually in the middle of the day, 

 or early morning when the leaves are partially damp 

 with dew. In cold weather it is nearly useless, and in 

 wet days the sulphur is soon washed off the leaf. The 

 general explanation of its action is that the sulphur be- 

 comes oxidized, w^ith the ultimate formation of sulphur- 

 ous acid, and this latter substance is credited with the 

 destroying effect upon the mold. Sulphurous acid, 

 however, in exceedingly minute quantities, has a del- 

 eterious influence upon the hop leaf itself. Some ex- 

 periments have indicated the formation of sulphureted 

 hydrogen. The fact that sulphur works most benefi- 

 cially on hot days, and also that the odor of a sulphured 

 garden is not like that of either sulphur dioxide or 

 sulphureted hydrogen, but resembles that of roll-brim- 

 stone itself, suggests that sulphur vapor may be the 

 active agent. The possibility that the action is a me- 

 chanical one must also be borne in mind. Some author- 

 ities state almost any fine powder will do, that road- 

 scrapings, brick-dust, chalk, and ordinary flour work 

 as well as sulphur. 



