332 BROOKLYN BOTANIC GARDEN MEMOIRS 
ease can be controlled for a long period of years in those localities 
where infection is not 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: (1) The 
disease has two hosts and can not pass from pine to pine. (2) The 
disease is a comparatively slow one; that is, slow as compared with 
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 undertaken regardless of the prevalence of the disease 
at the time, since wherever Ribes can be thoroughly eradicated healthy 
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 1mporting 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 pests are being 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 isa 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, 
