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THE BASIS OF PLANT DISEASE QUARANTINE RECOIMENDATIONS 
Prepared by N. Rex Hiont 
Why do we have quarantines on account of plant diseases? 
Why are seme plant disease quarantines prohibitory while others 
are restrictive only and why do restrictions vary? In general, 
what principles or basic facts are used as a guide by the plant 
pathologist in making quarantine recommendatians? 
Briefly, we have plant disease quarantines because they 
are profitable. 
Some quarantines are prohibitory because the plants protected 
represent major crops and the diseases concerned are destructive and 
cannot be kept out otherwise, some are restrictive because the 
diseases may be detected by practicable inspection or because an 
effective treatment is known. As diseases and their detection and 
treatments vary and plant materials and the type of treatment they 
may be given vary widely, it is necessary to impose equally varied 
restrictions. In general the plant pathologist should obtain as 
much pertinent data as possible regarding a disease and the plant 
material concerned and make his recommendation in accordance with 
the data, or lack of data. Now let us examine what is back of these 
statements. 
QUARANTINE PROFITS 
It is impossible to determine accurately the profits on foreign 
plant quarantines but the cost of eradication and control methods plus 
the losses resulting from the introduction of citrus canker, chestnut 
bark disease, potato wart, white pine blister rust, and Dutch elm 
disease, when compared with the annual cost of maintaining our foreign 
plant quarantines, shows that the average cost of one major plant 
disease when introduced is enough to finance the Division of Foreign 
Plant Quarantines for years. We intercept large numbers of major 
pests each year. How many of these would have succeeded in establishing 
themselves without our interference is problematical, but it seems a 
very modest claim to state that without the work of this division 
increased losses from introduced plant pests would be several times 
greater than the cost of the work. 
QUARANTINE ECONOMICS 
A quarantine costing more in cash, inconvenience or inter- 
national good will than the cash and aesthetic value of the plants 
protected would be unprofitable and indefensible. Large expenditures 
for quarantines to protect corn, wheat, potatoes, citrus fruits, 
forest trees, and our more important ornamentals are profitable. 
