6 CONNECTICUT EXPERIMENT STATION, BULLETIN NO. 178. 
is the best course to pursue under the particular conditions in 
which his woodlot is situated. 
CAUSE OF DISEASE. 
First of all, let it be clearly understood that the chestnut blight 
is caused by a fungus and not by an insect, as is often erroneously 
supposed. The fact that insects of various kinds are found in 
the dead bark of an affected tree has often led to the conclusion 
that the trouble is of insect origin, but such is not the case and 
insects have no part in causing chestnut blight. 
DESCRIPTION, 
The chestnut disease is caused by the fungus technically known 
as Endothia gyrosa var. parasitica. This fungous parasite pene- 
FIG. HM. BLIGHT STARTED TITROUGH INSECT INJURY (A), AND PRUNED BRANCH (B); 
C. MATURE FRUITING PUSTULES ON SMOOTH BARK, 
