[faull] presidential ADDRESS 13 



Other plant industries than there is of the abandonment of antiseptics 

 in the practice of surgery. The use of thoroughly tested measures of 

 control mean the exclusion of new diseases on the one hand, and on the 

 other increased yield and improved qliality by protection from those 

 already established. The lack of means of control has meant again 

 and again in the history of the past the wiping out of crops and even 

 the destruction of plant industries in many localities with resultant 

 disastrous social changes, while the application of means of control has 

 saved threatened areas from a similar fate, as in the case of Millardet's 

 rescue of the vineyards of France, and has made possible the restoration 

 of destroyed industries, as in the case of potato growing in parts of 

 Nova Scotia, or cabbage culture in Wisconsin. 



The problems of plant control fall under several rather distinct 

 heads, as: 



(a) Sprays and dips 



(b) Improvement of environmental conditions 



(c) Eradication 



(d) Exclusion 



(e) Breeding for resistance. 



(a) Dips and sprays and fumigations, that is chemical means of 

 disease control, including hot water treatment, have long been the 

 backbone of agricultural and horticultural phytopathological practice. 

 Nevertheless there is a call for more specialized investigations on this 

 subject. The method suited to one locality may require adaptations 

 if employed in other areas. Thus we find an outstanding potato dis- 

 ease expert recently stating with reference to established spray methods 

 for late blight: "in Nova Scotia it is nearly impossible to grow white 

 potatoes even with spraying." Why ? There is an answer to that 

 question. The same pathologist states that by improved methods 

 "we have grown white potatoes and kept them sound there in places in 

 Nova Scotia where such a thing was never known before." Too often 

 investigators on plant diseases have treated the spray question as an 

 incidental easily disposed of. One of the most absurd cases in point 

 was that of the sooty mold of tomatoes. Recent tests have shown 

 that the causal fungus of that disease flourishes undisturbed in standard 

 Bordeaux mixtures and other sprays that had from time to time been 

 recommended as prophylactics. Here as elsewhere the fundamentals 

 still ofïer wide scope for research. 



(b) The group of control methods falling under the head of 

 "improvement of environmental conditions" includes control of 

 moisture and light conditions both in the green house and in the field, 

 control of soil fertility, methods of cultivation, crop rotation especially 



