THE LIVING ENEMIES OF CROPS 59 



killed by putting the seed for three minutes into water at 

 a temperature of 57. This treatment costs nothing, 

 and may save much. Or the spores can be killed by 

 soaking for one hour in 5 per cent copper sulphate. 

 This substance, commonly called "blue vitriol," can be 

 bought for a small sum in any pharmacy. Either of 

 these treatments is likely to hasten germination. 



How Killed. Where a disease already exists on an 

 annual plant, that is, on a plant living less than a whole 

 year, it can be gotten rid of by completely destroying the 

 remains of the plants of any one season. If this is tried, 

 all the leaves and stems should be very carefully collected 

 and burned. 



This is sometimes the best way to fight a disease of 

 perennial plants also, but it is very expensive. How- 

 ever, all useless plants ought to be destroyed. For in- 

 stance, if the people about Lipa desire to raise coffee 

 again, they must first kill and burn the diseased coffee 

 plants that are now scattered along fences and in waste 

 fields. These are of no use whatever, and are as danger- 

 ous to healthy neighboring trees as a man with cholera 

 is to his human neighbors. If there are fields of coffee 

 too valuable to be burned up, they should be thoroughly 

 cleaned. All fallen leaves and branches as well as the 

 badly diseased trees should be collected and burned. 



Bordeaux Mixture. The spread of fungus diseases from 

 living plant to plant is prevented by means of Bordeaux 

 mixture. This mixture is so called because it was first 

 used near the city of Bordeaux, in fighting a fungus 



