THE FIGHT WITH THE FUNGI 53 



seriously enough to curtail the yield disastrously, but it did produce enough 

 diseased kernels to contaminate the flour for bread. 



Of course the disease was most serious in those years when the rye crop 

 was the shortest. In those years it was sometimes difficult to get rye that did 

 not contain ergot, and the people, especially the poor, had to eat it. These 

 were the years when St. Anthony's fire scourged the population. If wheat rust 

 had not been so serious in the warm, humid areas of central and southern 

 Europe, St. Anthony's fire might never have reached such gigantic proportions 

 and caused so much suffering and sorrow as it did during the Middle Ages. 



St. Anthony's fire began to decline in the eighteenth century and was only 

 occasionally serious in the nineteenth century. This decline in severity of 

 St. Anthony's fire was due to the rise of the potato as a source of carbohydrate 

 in Europe. People began to eat potatoes and reduce their use of rye. This 

 had a salubrious effect on St. Anthony's fire, but it led inevitably to one of 

 the most devastating famines of modern times, for which a plant disease 

 was again the cause. 



THE IRISH FAMINE 



Sir Walter Raleigh, visiting in Virginia in the early part of the seventeenth 

 century, discovered the Indians cultivating a plant, the name of which he 

 transliterated as potato. He took it to Europe where it remained a botanical 

 curiosity for a while. Eventually, the people began to eat it in some volume 

 and the crop spread rapidly across Europe. The peasant farmer of Europe soon 

 discovered that the potato would produce more carbohydrate per acre than 

 either rye or wheat. Slowly in some areas, rapidly in others, the potato re- 

 placed the cereals which had been the staple diet of the white men since the 

 dawn of history. Lush fields of green potatoes began to appear all over Europe, 

 instead of the nodding waves of wheat and rye. The potato was adapted to 

 as wide an area as any cereal, in fact, far wider than wheat. This shift from 

 cereals to potatoes was particularly prominent in Ireland; that's the reason 

 why we often refer to a potato as the Irish potato. Ireland was so densely 

 populated in the early part of the nineteenth century that the potato was a 

 godsend to them. The first thing anybody knew, Ireland had almost ceased 

 to grow cereal of any kind and was depending almost exclusively on the 

 potato. 



Just about one hundred years ago a new disease of potato appeared in 

 central Europe. It had never been seen before. It was a nasty disease; it made 

 the leaves suddenly turn water-soaked, slimy, rotten, and black. That wasn't 

 such a bad symptom except that the fungus that caused the disease spread 

 from the leaves into the tubers and caused them to decay with a very curious 

 and unusual sort of hard rot. The disease, which we now know as late blight, 



