ENDOTHIA CANKER OF CHESTNUT 
_ This disease has become the most destructive epiphytotic of tree 
diseases in this country. It is interesting in many respects. In the 
first place, the causal fungus is an importation, and the destruction caused 
is typical of what may often occur when new and unsuspected pathogenes 
are transferred to a different flora and climate. Secondly, it is as good an 
example of efficient correlation of parasite with its host and of extreme 
susceptibility of the host, as any disease could demonstrate. 
SYMPTOMS 
The lesions of this disease appear chiefly in the body and larger limbs 
of the tree. The symptoms are of two general sorts: the lesions or cankers 
themselves, and the secondary effects produced by these cankers in un- 
alae parts of the host. For convenience the latter are to be studied 
st. 
General symptoms. The diseased tree may often be detected at a 
distance by the following symptoms which are to be studied in the photo- 
graphs provided. oBSERVE:— 
1. That limbs with developing cankers, which have almost 
girdled them, do not produce normal leaves in the spring. They are 
usually lighter green in color and never develop to full size. This symptom 
is quite his during May and June. (See illustration photographs 
2 and 3. 
2. That dead leaves and last year’s burrs often hang to limbs 
which have been killed by the fungus during the summer. (See illustra- 
tion photographs 3 and 4.) 
3. The dead limbs, the death of which can be traced to distinct 
cankers, that are of the type described below. (See illustration photo- 
graphs 1, 2, 3 and 4.) 
4. The abnormal development of suckers on trunk or limbs. 
Examination may prove that these suckers grow from below a cankered 
area. (See illustration photographs 2 and 3.) 
Cankers. The normal healthy bark of the chestnut remains smooth 
and green for several years and thus the cankers are very distinct on young 
growth. In the material and photographs provided, NoTE:— 
5. That the cankers may be either sunken (necrotic) or raised 
and swollen (hypertrophic). (See illustration photographs 5 and 6.) 
6. That the surface of the diseased bark is always of a reddish 
cast, thus contrasting sharply with the green bark. (See frontispiece in 
Cornell Bul. 347.) 
7. That in a canker of the necrotic type, the bark is roughened 
and often split longitudinally; also the ‘‘pimples” or small eruptions all 
over the surface of the diseased area,—the fruiting stromata of the fungus. 
(See illustration photograph 5.) DRaw. 
8. That in a canker of the hypertrophied type, the outer bark 
is split longitudinally because of the abnormal development of the tissues 
beneath. (See illustration photograph 6.) DRAW. 
The sunken cankered area, reddish brown in color, is the usual evidence 
of the disease. When the fungus attacks rough-barked portions of the 
tree, its effects are not noticeable externally until the stromata of the 
85 
