A NATIONAL PLAN FOR AMERICAN FORESTRY 715 



This new disease has been under study by the New York authorities 

 for three seasons, but because of the complications entering into root- 

 disease investigation it may be several more seasons before we can 

 be certain of its antecedents or just what may be expected of it in 

 the country as a whole. This illustrates one of the weaknesses in our 

 preparedness against introduced diseases. We are yet so little 

 acquainted with the native diseases of our 180 commercial timber 

 species that when a previously unobserved diseased condition is found 

 it is often difficult to decide whether it is native or introduced. 



The newest threat is to the beech. A bark fungus of unknown 

 source has joined with a scale insect to destroy 40 percent of the 

 beech of Nova Scotia. Infection has now appeared in Maine, where 

 it is still very limited but is spreading with alarming speed. 



Serious as some of the foregoing cases are, there is some reason to 

 think that we have scarcely begun to suffer from introduced diseases. 

 To lose a single species from among our numerous forest trees is not 

 a complete disaster but to lose several from the same region might 

 very seriously cripple forestry both from the timber production and 

 the recreational standpoint. It is very probable that we already 

 have a large proportion of the dangerous fungi that were native to 

 Europe. Up to 1912 the United States Government had no legal 

 authority to exclude diseased propagating stock, and it was only 

 after the quarantine regulations of 1919 that the policy of free trade 

 in plant diseases really came to an end. However, considering the 

 great number of forest species related to ours which are found in 

 Asia, and the relatively small amount of commerce which we have 

 had with Asia, Africa, and South America until recent years, it is 

 probable that we have thus far been exposed to relatively few of the 

 potential tree-disease organisms of those continents. 



Diseases brought in before 1919 may yet remain to be discovered. 

 A single importation of a disease, even if it be a virulent one, seldom 

 spreads far enough to be discovered or brought to the attention of 

 our small staff of forest pathologists. until it has been in the country 

 at least 10 or 15 years. While the quarantine regulations now in 

 force have undoubtedly prevented or greatly delayed the introduction 

 of pests since 1919, no system of quarantine which it is possible to 

 enforce at present can guarantee absolute exclusion of new diseases 

 indefinitely. Yet every delay in introduction is vastly important, 

 not only because it avoids damage or costly readjustment to the in- 

 truder but also because we are likely to be able to meet the newcomer 

 in the future with a more organized and efficient effort than can now 

 be directed against it. Complete enforcement is impossible, and 

 quarantines cannot be applied to some kinds of imports without 

 excessive interference with commerce. For example, it appears 

 impracticable to limit the importation of wood in the form of logs, 

 pulpwood, or packing cases, though there is considerable possibility 

 that these imports may bring with them tree diseases of the vascular- 

 wilt type exemplified by the maple wilt and the so-called Dutch elm 

 disease, as well as fungi that will add to our deterioration problems in 

 forest products. Few introduced organisms would be as easy to 

 control as the blister rust. From the nature of the case, any predic- 

 tion is highly speculative, but the probabilities favor trouble from 

 now unknown foreign diseases for others of our important tree species. 



