70 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Against mildews, we have the ammonium polysulphide wash, dis- 

 covered three years ago at Wye College. This wash, unlike lime- 

 sulphur, leaves no visible deposit on the parts sprayed, and is there- 

 fore extremely useful for spraying gooseberries against the American 

 Gooseberry-mildew when the fruit is to be picked soon. 



Then we come to lime-sulphur — perhaps the most widely used of 

 all fungicides. I have an interesting announcement to make with 

 regard to this wash. As is well known, when lime-sulphur is used as 

 a summer spray on foliage and fruit, it is very difficult, even when 

 using a nozzle giving the finest " misty " spray, to get the wash dis- 

 tributed evenly over the surface of the sprayed parts ; the deposit 

 when dried is found to be " blotchy." Recent experiments carried 

 out at Wye College show that this difficulty is entirely removed if a 

 small quantity of saponin in solution is added to the lime-sulphur 

 wash. If the lime-sulphur wash contains 0 05 per cent, saponin it 

 will be found that the dried sediment is in the form of a practically 

 continuous film over the sprayed surface. Soap — the usual spreading 

 agent — cannot be added to lime-sulphur for chemical reasons, but by 

 means of the addition of saponin we are able to improve greatly the 

 spreading power of lime-sulphur, which should in consequence prove 

 a better protective wash. Also, by the substitution of a thin film 

 instead of " blotches," there is much less disfigurement of sprayed fruit. 



Another point I should like to mention with regard to lime-sulphur 

 concerns its composition. Our experiments have shown that the 

 fungicidal properties of the ammonium polysulphide wash depend 

 upon the polysulphides present. We are now investigating the action 

 of the polysulphides of the lime-sulphur wash, and it is probable that 

 the strength of lime-sulphur washes will be able to be determined on 

 the basis of the percentage of its polysulphides. This will be a much 

 more scientific basis for standardization than the present specific 

 gravity test. 



In concluding, I should like to express my opinion that the prospects 

 of growing clean fruit in this country have never been so good as they * 

 are at the present time. 



Fifteen years ago — when I joined the staff at Wye College — very 

 little was being done in Kent to control fungus diseases. The cause of 

 "black-spot" or "apple-scab," of "silver-leaf," and of "brown-rot," 

 was quite unknown to the average grower ; Bordeaux mixture was 

 unknown except for use on potatos ; lime-sulphur had not been 

 introduced from America ; the nozzles in use were those employed 

 for hop-washing and only suitable for the application of coarse sprays. 

 At the present time we find both the farmer and his foreman using 

 magnifying-glass to identify the fungus and insect pests ; in several 

 places in Kent we see platforms erected for the making of Bordeaux 

 mixture from " stock solutions " ; lime-sulphur is in common use, and 

 many farmers understand the use of the hydrometer in connexion 

 with its dilution ; the spraying machines and the nozzles in use are 

 equal to the best made in other countries. 



