808 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



so I will not condemn any, except in general terms, and say that the 

 ready-made stuff that you buy is not as good as the mixture you make 

 yourself at the moment— that is, if you make it properly. 



Many of the arguments often brought forward in favour of spraying 

 will scarcely bear examination. Some one will write to the paper and 

 say : "I spray my orchard and have not a trace of disease." Perfectly 

 true ; there might not have been any if it had not been sprayed. But 

 evidence of that kind is absolutely of no value whatever unless you have 

 some of the orchard left for comparison. Spray half your orchard and 

 compare notes, then you can say whether your spraying has been effectual, 

 and to what extent it has been effectual. You can even go to percentages. 

 I do not think very much of figures ; they are not always convincing ; 

 still if you have a control, you may take it for granted that other things 

 being equal the sprayed portion of the orchard would have been as badly 

 diseased as the unsprayed if it had not been sprayed, so that if there 

 is any beneficial result it is clearly indicated ; but when all the orchard 

 is sprayed, there is no check whatever. It must be admitted, I think, that 

 there are orchards that go through the season without any serious disease. 

 We have not reached that pitch where every orchard is badly infected, 

 by any means. 



Another argument urged in favour of spraying is that, apart from 

 the fungicidal properties of the spray, the plant itself is benefited — 

 in what way has not been quite explained. Many people say : " My 

 crop was so much the better for spraying, apart from its fungicidal 

 action ; the plants had no disease." This is, of course, generally brought 

 forward, more especially in connection with potatos. Some people 

 spray, and probably it pays them to spray ; they say that the foliage 

 lasts longer, and consequently does more work and gives a better crop, 

 other things being equal, when the crop is sprayed twice during the 

 season. That may be perfectly true. I have no evidence either for or 

 against it. I accept it as a statement ; but certainly, so far as spraying 

 potatos is concerned, I am very doubtful whether any benefit can be 

 derived. The disease comes and appears on one portion of the foliage 

 in a particular part of the field. The spray is of value in preventing 

 the spread of that disease, so it is of value to the extent of check- 

 ing what would naturally and undoubtedly have taken place if no 

 spraying had occurred ; but at the same time we find, I am firmly con- 

 vinced, that there is not a tuber in Great Britain that is free from the 

 ordinary potato disease. A celebrated German scientist has gone to the 

 • extent of saying there is not a tuber in Europe free from it. I am not 

 inclined to argue even on that point. There is one qualification to be 

 made, however ; of course with a plant that is derived from seed (into 

 which the mycelium has not been known to pass) the tubers will be free 

 from disease ; but a tuber which has been in the ground for more than 

 two seasons in all probability has become diseased, that is, it has mycelium 

 within it. We may have many seasons without any potato disease, 

 practically speaking, but that does not prove that the disease, or con- 

 ditions favourable for producing disease, is not in the potato. It only 

 means that external conditions favour the potato and check the growth of 

 the fungus. Every practical man knows to<< it only requires three muggy 



