THE RELATION OF PLANT PATHOLOGY TO HUMAN 
WELFARE! 
F. L. Stevens 
(Received for publication January 17, 1921) 
In the present era of high cost it is especially fitting that one take 
account of all expenditures, and weigh carefully the returns. With the 
present underpaid and poorly equipped condition of many educational 
and research institutions, and especially in the light of certain criticisms 
that are made regarding research, I am impelled today to select from the 
many interesting themes which might be developed regarding plant pathol- 
ogy, and to direct thought to research in the science of plant pathology and 
its related fields, and briefly to indicate the returns therefrom. 
Plant pathology is preeminently a practical science, and its prime func- 
tion is to guide the way to an ever-increasing control over disease. 
The magnitude of the annual loss incurred in the United States alone 
through plant disease in diminution of yield and loss of produce is far 
greater than it is generally conceived to be. I shall not burden you with 
statistics, but I do wish to give a few examples, taken from the most reliable 
estimates that have been made, to indicate the loss. Thus, in the various 
Plant Disease Survey Reports we find that for the year 1919 losses from 
plant diseases are given as follows: For the five leading cereals 482,695,000 
bushels; for potatoes 86,997,000 bushels; for tomatoes 307,168,000 bushels; 
for sweet potatoes the loss is put at 58,841,000 bushels, or more than one 
half the crop. You are all familiar with the diseases mentioned; but you 
fail to get the world bearing of plant-disease ravages unless you include in 
your vision such destructive diseases as the coffee rust, affecting in disastrous 
form a crop of large world value, which in two years destroyed 272,000 
acres in Ceylon ; the banana wilt, which is reported to have caused abandon- 
ment of nearly 20,000 acres of banana plantings in Panama alone and to 
have rendered useless large railroad lines; the cocoanut palm bud-rot, 
which kills the growing point of this valuable tree and which is rapidly 
encircling the world. 
Your imagination may fairly picture similar diseases as occurring 
throughout the world on the whole range of useful plants. Before harvest 
disease may devastate the crop in the field, and after harvest the inroads 
proceed in storage. Obviously the loss occasioned by destruction of the 
product at market is far greater per unit than similar losses in the field. 
^ Invitation paper read before the joint session of Section G, A.A.A.S., the Botanical 
Society of America, and the American Phytopathological Society, in the symposium on 
"The Relation of Botany to Human Welfare," at Chicago, December 29, 1920. 
315 
