CONTROL OF THE CHESTNUT BARK DISEASE. 13 
very obscure. Practically no sign of the disease is visible from a dis- 
tance, except in those cases where the burs persist on the older trees. 
Even the pustules of the fungus become weathered, so that even a 
close examination of a tree may not yield visible results. But the 
destruction of trees already marked can continue through the winter. 
Destroying advance infections——Many of the advance infections 
will be found to consist of single trees or of less than half a dozen 
trees. These may perhaps be destroyed by the person who finds them, 
especially if remote from other infections; but the greater part of 
the work of elimination is best handled by other persons under sepa- 
rate direction. Undoubtedly this work can be best directed in each 
‘State by the State forestry officials. gi 
The work of elimination should be done as soon as possible after 
the diseased trees are located, but may be done at whatever time of 
year is most convenient, since new infections will be detected by the 
scouting of the following year. The marked trees should be cut 
down. So far as is now known, the timber may be safely utilized in 
various ways, provided it is barked. The bark and brush should be 
piled over the stumps and, as soon as practicable, burned. If it is 
not practicable to have the fire over the stumps, the stumps should 
be barked to the ground; but in any case the bark and brush must 
be burned. 
It will be readily seen that the task of locating the disease, and the 
subsequent one of eliminating it, call for very different talents. The 
“ scouting” calls for carefully trained and absolutely accurate scien- 
tific observers working under the most highly specialized direction 
that can be obtained. The work of elimination calls not for scien- 
tific knowledge, but for executive ability, tact in dealing with 
owners and in otherwise administering the law, and a knowledge of 
forestry and of lumbering, market, and transportation conditions. 
In a word, the first is a task for pathologists, the second for foresters. 
Another advantage of thus dividing the work is that a certain rivalry 
will usually develop, resulting in more thorough work on both sides. 
It is, moreover, of the utmost importance to have as many different 
forces and interests as possible in any given State working toward 
the common end of controlling this disease. 
Establishing the “immune zone.”—After all advance spots of 
infection are eliminated, attention must be turned to the main line 
_ef advance—the edge of the area of general infection. Here the 
problem will present local differences. It may prove necessary in 
some States to destroy all chestnut trees, diseased or healthy, in a 
belt 10 to 20 miles wide, or possibly less. Advantage must be taken 
of natural barriers to infection, such as unforested areas or wooded 
areas without chestnuts. In this way an “immune zone” will be 
established, across which the disease can not easily be transmitted by 
467 
