414 PLANTS AND MAN 



rye, which are infected with a fungus disease called ergot, caused 

 untold suffering and famine in Italy, France, and Spain during 

 the middle ages. France again suffered nine epidemics of this 

 disease in the seventeenth century and seven in the eighteenth, 

 while Germany experienced twenty one outbreaks of ergotism 

 in the eighteenth century alone. The human disease is of two 

 types, the one known as gangrenous ergotism which causes the 

 body extremities — fingers, toes, nose and ears — to become gan- 

 grenous, ultimately progressing to cause death, and the other 

 called convulsive ergotism, which affects the nervous system and 

 brings about convulsions, delirium and finally death. 



The great potato blight in Ireland during the years 1843- 

 1 845 resulted in the death of one quarter of a million people as a 

 result of starvation and sickness, and started a fifty year emigra- 

 tion, totalling over one and one-half million people, to the 

 United States. The powdery and downy mildew diseases of 

 grapes practically extinguished the wine industries of various 

 parts of Europe during the late nineteenth century, necessitating 

 a complete change of farming and produce among the inhabit- 

 ants of the affected regions. Within the short space of a decade 

 a leaf disease of the coffee tree wiped out this once flourishing 

 industry on the Island of Ceylon which is now devoted to the 

 growing of cocoa and tea. The notorious chestnut blight 

 disease, first found in New York in 1904, has swept the range of 

 our native American chestnut trees, and there is little hope of 

 avoiding extinction of this once valuable and important United 

 States timber tree. Not only do the forest owners feel the loss 

 of this tree, but telephone and light companies who formerly 

 used chestnut poles, as well as the tanning industry to which 

 chestnut formerly furnished 90% of its native tanning extracts, 

 are likewise affected. Thus these minute fungus plants become of 

 great importance in their relation to the affairs of mankind 

 through their effects upon his agricultural and forest products. 



Although fungi cause the most destructive of plant diseases, 

 they are not the sole causal agents. Indeed, a whole host of 

 diseases are due not to the attack of plant or animal organisms, 

 but rather to conditions or factors in the plant's surroundings. 

 These diseases are generally referred to as non-parasitic maladies, 



