April, '12] METCALF: CHESTNUT BARK DISEASE 225 



No definite evidence, experimental or otherwise, has been adduced 

 to show that a tree with reduced vitality is more susceptible to infec- 

 tion, or that the disease spreads more rapidly in such a tree, than in a 

 perfectly healthy and well-nourished tree of either seedling or coppice 

 growth, provided that such reduced vitality does not result in or is 

 not accompanied by bark injuries through which spores can gain 

 entrance. 



The control of the disease. From the standpoint of pure science, 

 we are not equipped to cope with the situation as it presents itself. 

 The disease attracted no attention until 1904, and it was not until 

 3 years later — 1907 — that an office was organized in the U. S. Depart- 

 ment of Agriculture for the exclusive study of forest and ornamental 

 tree diseases. Great conservatism has prevailed regarding the conta- 

 gious nature and seriousness of the disease. Local investigators have 

 paid little attention to its practical aspects. Obviously, treatment 

 must be more or less empirical, and based upon analogies with general 

 sanitary methods rather than upon accomplished experiments. For 

 while experiments have been made on the method of control by' elim- 

 ination of advance infections, and have so far been successful, they 

 are too few in number and too local in distribution to be absolutely 

 conclusive. Yet they are indicative, pointing strongly to the ultimate 

 success of the method of elimination of advance infections. 



If extensive practical investigations of this disease could have 

 begun in 1904 or earlier, we would now have a body of knowledge upon 

 which we could base accurate and final conclusions. And such research 

 could have been conducted at a very small expense — a mere fraction 

 of the property loss already caused by the disease. But now it is 

 too late to merely experiment. It is an old law in the practice of 

 medicine, that when the patient is already moribund, the best remedy 

 that presents itself must be applied, whether conclusively proved to 

 be efficient or not : and this law applies equally well to plant pathology. 

 The method of cutting out advance infections is open to many criti- 

 cisms, but so far no other method of dealing with the situation has 

 been even proposed. 



For legal reasons, the actual elimination of the advance infection 

 must be done under state, not national, authority; and for this reason 

 responsibility for action or inaction lies with the several states in which 

 the chestnut tree is a valuable asset. So far the only state to take 

 up the problem vigorously is Pennsylvania. In this state the work is 

 being carried on under a special law. In may other states, as in New 

 York, the work can doubtless be carried on under the existing crop 

 pest laws. 



For more complete discussion of control methods, reference is made 



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