2 DISEASES OF TROPICAL PLANTS 



from him until they become destructive to his crops. 

 The fact that the disease which is of little importance 

 to-day may become very destructive in the near future, 

 does not excite most growers to use the precautionary 

 measures necessary to prevent the spread of these 

 diseases. A good crop attracts the attention, and proves 

 so satisfactory to the average grower that he fails to see 

 heavy losses which could be prevented at very small cost 

 in time and money. 



Plant diseases were mentioned by Aristotle in his 

 writings about 350 B.C., and have been referred to by 

 various writers since that time, but did not receive much 

 attention until about the middle of the last century ; and 

 the greatest development has been within the last 

 quarter of a century. The workers for many years 

 could be divided into two groups, the botanists who 

 were interested in the study of the organisms which 

 caused the diseases and the practical growers who were 

 interested in finding remedies. In most cases very 

 little could be done towards securing a remedy until the 

 cause was known, although in some cases remedies have 

 been devised with a very incomplete knowledge of the 

 organism causing the disease. Very little progress was 

 made in the treatment of diseases previous to 1882, 

 when the value of lime and copper sulphate as a fungicide 

 was accidentally discovered, and very quickly resulted 

 in the development of Bordeaux mixture, which is now 

 used extensively throughout the world, especially in 

 fruit-growing districts. 



It was the custom of the grape-growers of some 

 parts of France to sprinkle the grape vines near the 

 road with a mixture of milk of lime and copper sulphate 

 (bluestone), to give them the appearance of being 

 poisoned, and thus prevent the encroachments of petty 

 thieves. In 1882 Prillieux and Millardet observed that 

 the vines which were thus treated were comparatively 

 free from the downy mildew (Plasmopora viticola), a 

 fungus that had been introduced from America, and 

 which was causing heavy losses to the grape industry. 



