FACTS NOT GENERALLY KNOWN 23 



parasite become that the cultivation of coffee had to be 

 abandoned. At a later date coffee plantations have been 

 established in Natal and German East Africa, but the same 

 kind of fungus has proved destructive there also, and on 

 investigation it has been shown that the Hemileia is also 

 present on native trees in Africa belonging to the coffee 

 family. 



FACTS NOT GENERALLY KNOWN 



However frequently and however well spraying is done, it 

 should always be considered as nothing more than a supple- 

 mentary aid towards the prevention of disease. Take, for 

 instance, the too well-known scab of apples and pears, for the 

 prevention of which spraying is perhaps more generally 

 practised than for any other disease in Britain. The fact has 

 now been generally accepted that this disease is caused by a 

 fungus, hence many people commence by spraying the quite 

 young fruit, for the purpose of destroying the fungus spores 

 that alight on its surface. Other people, possessing a little 

 more knowledge on the subject, spray the young foliage some 

 time before the fruit is set, knowing that as a general rule, the 

 fungus appears on the leaves before it does on the fruit, and 

 that it is the spores produced on the leaves that are washed 

 by rain, etc., on to the young fruit. This is one step in 

 advance, but not sufficient. How many people know, or if 

 they know, act on the knowledge that the fungus first forms 

 spores on dead terminal shoots, that the spores formed on 

 such dead twigs infect the young leaves, and from thence pass 

 to the fruit. Now no amount of spraying will kill the mycelium 

 of the fungus present in the dead shoots, hence some other 

 remedy is necessary. Such remedy is only to be found in the 

 removal of all dead tips of shoots during the winter, before 

 the spores are produced. As a further safeguard, spray just 

 when the leaves are expanding, as it may safely be assumed 

 that certain infected branches have been overlooked. 



Black scab or warty disease of potatoes is perhaps more 

 destructive than the original * potato disease ' caused by 

 Phytophthora infestans. Yet many people collect diseased 

 potatoes and throw them into the piggery, realising that the 

 pigs may benefit a little by eating them. Probably the pigs 

 do benefit to a certain extent, but if the owner knew that 

 the spores present in the scabbed potatoes passed through the 



