'hop-mould' 75 5 



Some experiments have indicated the formation of sulphuretted 

 hydrogen. 



The fact that sulphur acts most beneficially on hot days, 

 and that the odour of a sulphured garden is not like that of 

 either sulphur dioxide or sulphuretted hydrogen, but resembles 

 that of roll-brimstone itself, suggests that sulphur vapour may be 

 the active agent. 



The possibility that the action is a mechanical one must also 

 be borne in mind. Some authorities state almost any fine 

 powder will do, that road-scrapings, brick-dust, chalk, and 

 ordinary flour work as well as sulphur. 



However, until we have more definite investigation of the 

 action of sulphur powder upon the mycelium of the fungus, all 

 explanations are little more than assumptions, and we are not 

 likely to find a satisfactory or consistent and reliable method of 

 applying sulphur to the best advantage. 



(e) Under the assumption that sulphur has some specific action 

 upon the fungus, various ' soluble compounds containing the 

 ingredient are employed, chiefly the sulphides of sodium, calcium, 

 and potassium (' liver of sulphur '). These substances are, 

 undoubtedly, of considerable use in checking and destroying 

 ' moulds ' of all kinds. They are readily soluble in water, and are 

 generally applied in the ordinary washes of soft soap and quassia 

 at the rate of one and a half or two lbs. per loo gallons of wash. 



A wash of this description, followed by an application of 

 powdered sulphur, is perhaps the most effective and safe means 

 known at present for an attack of ' mould.' 



The alkaline sulphides in solution do not keep well, unless air 

 is excluded from the vessels in which they are kept. Without 

 going into details it may be said that practically all ' mould ' 

 washes have, as a basis, one or more of the above sulphides 

 in conjunction with substances like soap and glycerine, which tend 

 to keep the wash upon the leaf till it has done its work, and which 

 also prevent too rapid oxidation of the active ingredient. 



