332 BROOKLYN BOTANIC GARDEN MEMOIRS 



ease can be controlled for a long period -of years in fhose localities 

 where infection is no^ general but in areas of general infection the 

 control will be only local and the efficiency of this local control will 

 largely depend upon whether the white pine as a crop is of sufficient 

 value to sustain the added expense of the eradication of Ribes. It 

 is to be hoped that any infections found west of the Mississippi River 

 will be scattering and small, for, as has already been stated, if the 

 disease once becomes established under western forest conditions 

 its control even on a local basis will be absolutely out of the question. 

 Two facts are always in favor of the control of this disease: (i) The 

 disease has two hosts and can not pass from pine ta pine. (2) The 

 disease is a comparatively slow one; that is,- slow as compared wnth 

 such a disease as the chestnut blight. If at any future time in a 

 completely infected locality the increasing value of the white pine or a 

 change in industrial conditions makes local control profitable such 

 control can be undef taken regardless of the prevalence of the disease 

 at the time, since wherever Ribes can be thoroughly eradicated hearlthy 

 pine stock can be grown and will not take the disease from the already 

 diseased pines. 



The entire blister-rust problem is, however, but one phase of a 

 larger problem, which may be stated as follows: does free trade in 

 plant diseases and insect pests pay? Is it an economically sound 

 national policy? Is the entire importing nursery business worth as 

 much to the country as the -damage which it has already caused? 

 Not a single plant disease or insect pest that has once become estab- 

 lished in^this country has been eradicated or, in the present state of 

 knowledge, is ever likely to be. No matter how well controlled, it 

 remains in every case a permanent tax against our economic resources. 

 Even if we succeed in controlling the white pine blister rust we may 

 be absolutely certain that other diseases and pe^s are bieing intro- 

 duced which will be just as serious, "for we. know definitely that the 

 undesirable plant immigrants are not yet all here. It is much more 

 important to safeguard the country against further invasions of this 

 kind than to control this or any other disease or pest that has already 

 been carelessly permitted to establish itself. 



It is a matter of common knowledge, which I scarcely need to repeat 

 here, that the countries of Europe, and even ends of the earth like 

 Tasmania and South Africa, have long since protected themselves 

 against the importation of" diseases and pests either by prohibition of 

 entry of nursery stock, or by exclusion of large classes of such stock. 

 The United States is far behind in this matter. 



The future danger is far greater 'than the present. The most 

 dangerous class of nursery stock is the ornamental trees and shrubs, 



