CONTROL OF THE CHESTNUT BARK DISBASE. 9 
a somewhat characteristic reddish-brown color, which can easily be 
detected at a long distance. Later this leaf coloration changes to 
a more brownish tinge and the leaves are commonly persistent for a 
considerable time. The chestnut fruits (burs) on a spring-girdled 
branch may or may not attain full size, according to whether the 
girdling by the disease was completed late or early in the spring. 
These burs commonly persist on the tree during the following win- 
ter, thus producing the only symptom which is at all conspicuous 
during the leafless season. The great damage which the disease has 
done in the late summer thus becomes most evident at the beginning 
of the next season, and that done in the spring becomes evident later 
in the same season, giving rise to the false but common idea that 
the fungus does its work at the time of year that the leaves change 
color, when in reality the harm was done much earlier. 
Perhaps the most easily seen as well as the longest persistent 
symptom of the bark disease is the prompt development of sprouts, 
or “suckers,” on the trunk of the tree (fig. 2) and at its base, or 
somewhat less frequently on the smaller branches. Sprouts may 
appear below every girdling lesion on a tree, and there are usually 
many such lesions. These sprouts are usually very luxuriant and 
quick growing, but rarely survive the second or third year, as they 
in turn are killed by the fungus. The age of the oldest living sprout, 
as determined by the number of its annual rings, is an indication of 
the minimum age of that portion of the infection immediately above 
it. Sprouts are sometimes produced as a result of other injuries; 
for instance, trees girdled by borers may develop sprouts, but these 
are generally less rapid in growth and are distributed with greater 
uniformity over the trunk. 
MEANS OF SPREAD AND ENTRANCE. 
The disease is spread by the spores of the fungus, of which there 
are two kinds. As both kinds of spores appear to be sticky, there 
is no evidence that they are transmitted by wind except where they 
may be washed down into the dust and so blown about with the 
dust. The spores are spread easily through short distances by rain; 
particularly they are washed down from twig infections to the 
lower parts of the tree. There is strong evidence that the spores 
are spread extensively by birds, especially woodpeckers, and there 
is also excellent evidence that they are spread by insects and by 
various rodents, such as squirrels. The disease is carried bodily for 
considerable distances in tan bark and unbarked timber derived from 
diseased trees. One of the most prolific sources of general infection 
has been the transportation of diseased chestnut nursery stock from 
infected to uninfected localities. 
8118°—Bull. 467—11——2 
