144 ILLINOIS STATE ACADEMY OF SCIENCE 



careful scientific consideration or the application of well- 

 advised prevention or control programs. 



Certain methods maj^ be of use in this kind of determi- 

 nation. In the first place, there should be secured in 

 large quantity data showing the percentage of infection 

 upon individual plants. To this should be added data 

 showing the percentage of diseased individuals in sepa- 

 rate fields, and the i^ercentage of diseased fields in a 

 county. A correlation of this information, based upon 

 expected yield, with the actual yield, will lead to rela- 

 tively accurate determination of the damage done. 



COBRELATED ACTIVITIES 



While the importance of the Plant Disease Survey lies 

 chiefly in its ability, through its attention to the distribu- 

 tion of disease and its other studies, to direct attention 

 to those diseases which are of a j^articularly dangerous 

 nature, so that proper control measures may be devel- 

 oped or applied at the proper time and in the proper 

 places, according as the need may be, there are in addi- 

 tion a number of possibly less important but none the 

 less vitally needed lines of endeavor which must of neces- 

 sity fall within its scope. Several of these have been men- 

 tioned in previous paragraphs, but a grouping of them at 

 til is point will serve to emphasize them in their proper 

 relation. 



In bringing together observations concerning the ori- 

 gin of diseases and their relation to the weather, tempera- 

 ture, moisture, etc., there seems to be some justification 

 in supposing that attempts, in a small way, may soon be 

 made toward the forecasting of outbreaks of diseases, 

 and that this may be increased as time goes on and data 

 becomes more generally available. The coupling of this 

 possibility with timely warnings concerning the preven- 

 tive measures which may be advisably applied would 

 render a service of real value from an economic stand 

 point. 



Since the survey is concerned with all parasitic dis- 

 eases of plants, it becomes its duty to develop an her- 

 barium containing specimens of all diseases occurring 



