PAPERS OX BIOLOGY AND AGRICULTURE 141 



THE ILLIXOIS PLANT DISEASE SURVEY 



Leo E. Tehox, State Xatueal History Suevey 



ixteoductiox 



AVlierever agricultural pursuits are followed to an ex- 

 tent that is nationally important, plant diseases demand 

 a large amount of attention because of their destructive 

 charact-er. The establishment in July, 1921, of a Plant 

 Disease Survey in Illinois is a recognition of this fact. 



It is the purpose of this paper to present to the Acad- 

 emy of Science an outline of the problems which lie 

 within the pro^'ince of the survey, and to summarize 

 the results of the first season's work. 



The Plant Disease Survey is one of the activities car- 

 ried on by the State Natural History Survey in its pro- 

 gram of study of the biological phenomena of Illinois. 

 The purpose of the survey may be outlined as being 

 concerned with three chief tasks : 



1. To ascertain what diseases occur within the state 

 of Illinois. 



2. To study their distribution throughout the state. 



3. To determine how much damage they do. 



So broad a generalization as this enumeration indi- 

 cates may best be defined within its limits through a 

 more detailed examination of the lesser tasks involved 

 in each of the above. 



ASCEETAIXIXG WHAT DISEASES OCCUR 



Plant diseases may be classed, for our present pur- 

 pose, as being either important, or unimportant, from 

 an economic point of view. Whatever disease attacks 

 a plant grown for its agricultural value whether or not 

 it is, in itself, serious, must be considered as an economic 

 disease, for it adds in some measure directly to the total 

 crop loss of the state from plant diseases. It is essen- 

 tial, therefore, that all diseases of crop plants shall re- 

 ceive some attention. The amount of attention may, 

 however, be distributed either in accordance with the 

 value of the crop or the importance of the disease to the 

 ■crop. One would expect to pay but little attention to the 



