104 THE PLANT WOELD. 



FIELD WORK I:Nt PLANT PATHOLOGY.* 



By Professor F. D. Heald. 



Field A\ork is of great importanee, both in the study of in- 

 organic (non-parasitic) and organic (parasitic) diseases, but 

 laboratory work must still continue to receive its full quota of 

 time. In these days of fads and extremes I fear that the lab- 

 oratory side of pathology may l)e neglected; tlie laboratory must 

 not be deserted for the field, but the studL'ut nmst spend time in 

 both. Sometimes field work must predominate, but at other 

 times the work will be largelj- confined to the laboratory and 

 greenhouse. 



In the study of diseases due to unfavorable climatic, 

 edaphic, or Iddlogic factors, the questions to ])e treated arc 

 largely those of abnormal physiology, and wliile much can be 

 done in these troubles in the laboratory and greenhouse, many of 

 the problems to be solved can only be worked out under field 

 conditions, using accurate quantitative methods. 



The methods to lie employed are essentially those of plant 

 physiology, with the incorporation and acblition of methods that 

 more properly belonged to metcorobigy, agronomy, soil investi- 

 gation, agricultural chemistry, horticulture, and possibly geol- 

 ogy also. In short, the student who expects to investigate this 

 class of diseases must use those methods which have been called 

 "ecoloo'ical methods." 



If field work is important in the study of the so-called ''in- 

 organic diseases," it is equally important in the investigation of 

 diseases due to parasites. Limiting the remarks to the diseases 

 of fungus or bacterial origin, the following important lines of 

 field work may be mentioned : 



1. Observation of diseases, and collection of material. 



2. Determination of the extent of injury. 



3. Experimental and demonstration work in the prevention 

 and treatment of diseases. 



*Written from the notes of an address given before the Botanical 

 Seminar of the University of Nebraska. 



