354 READINGS IN BIOLOGICAL SCIENCE 



at the Experiment Stations have been working to breed varieties of wheat 

 that are resistant to the stem-rust fungus. They have been able to combine 

 rust resistance with the other quahties we need in wheat, — high yields, 

 drought- and cold-resistance, and good milling and baking qualities. Jim 

 Beard, out west of town, has been growing one of these varieties, and it's 

 making thirt)^-seven bushels to the acre this year. You can get some of 

 that wheat for seeding, and be ready for rust another year." 



Because disasters like this occur today and often mean the difference 

 between success and failure in agriculture and because many such disasters 

 can be averted by timely intervention of simple preventive measures, some 

 acquaintance with the science of plant pathology is indispensable to agri- 

 cultural workers. 



You are studying a comparatively new science, that of plant disease. It is 

 only a few decades since plant pathology came into being. Some of the 

 pioneer plant pathologists, founders of the science in America, are still 

 vigorously carrying on their warfare against plant disease, setting a stimu- 

 lating example to their army of young followers. But plant diseases them- 

 selves, and their prevention by empirical or intuitive recipes, are by no 

 means limited to problems of today. Long before the appearance of civilized 

 man, the agents of disease were leaving petrified thumbprints in the fossils 

 that tell us of the leaf spot diseases and other ailments of prehistoric vege- 

 tation. Among the earliest written records of man, the unmistakable com- 

 plaints of blights, mildews, and plagues show us clearly that plant disease 

 has shadowed the agricultural path of man since he first scratched the soil 

 with a pointed stick and planted seed. The Old Testament tells us of plant 

 diseases visited upon man in punishment of his transgressions. Three hun- 

 dred years before Christ, Theophrastus, the Father of Botany, was well 

 famihar with plant diseases of his time, and in his writings we can recognize 

 many of our plant troubles of today, scorch, rot, scab, and rust. So formida- 

 ble were the cereal rusts in those early days that the Romans evolved a pair 

 of rust Gods, Rubigus and Rubigo, whom they annually honored as a 

 means of rust prevention. 



As ancient times gave way to the intellectual darkness of the Middle 

 Ages, these early sparks of understanding of plant disease were all but 

 extinguished by the superstition and avoidance of reason that over- 

 shadowed that period. Plant diseases continued to take their toll from the 

 European peasant and landowner, but we learn httle of them save that 

 from time to time great epiphytotics * occurred, attended by disaster, 

 famine, and migrations, and historical documents of the early days tell us 

 of entreaties to The Diety to ward off the evil blights, of tragic suffering 

 and death from the "holy fire" which we now attribute to the eating of 

 ergot-diseased grain, of the suffering and famine in Ireland when disease 



• The name given to a destructive outbreak of plant disease; comparable to epidemics 

 of human disease or epizootics of animal diseases. 



