June, 1955 
Fig. 1—Examining a wilt-killed oak tree for 
mycelial mats. 
Cur_: Oak Witt INocuLA 281 
loose, and the condition of the wood ap- 
peared to be slightly beyond the optimum 
for mat development. These trees had 
wilted early in June. 
Examination of Trees 
Both standing and felled trees were 
studied. Five trees, four red oaks and one 
black oak, were felled to determine the 
ability of the fungus to fruit on felled tim- 
ber. The remaining 25 trees were left 
standing so that a study might be made of 
their natural decline and the development 
and deterioration of mycelial mats under 
natural conditions. 
Examination of the standing trees to 
heights of 20 to 55 feet was facilitated by 
ladders, fig. 1, constructed on the trunks 
with green oak slabs obtained from a saw- 
mill. A lineman’s safety belt, usually with 
a one-half-inch rope attached, was used as 
an added safety precaution. Climbing 
spurs were not used because of the treach- 
erous nature of loose bark on dead trees. 
The ladders facilitated thorough examina- 
tion of the entire main trunks of trees with 
relative ease and provided safe positions 
from which some of the lateral branches 
could be examined. 
As excessive removal of bark might have 
caused infected trees to dry out before 
mats had a chance to form, these fruiting 
bodies of the fungus were located at first 
only by tapping the bark. This proved to 
be a surprisingly accurate method; in 
nearly every spot where the bark gave a 
dull, hollow sound when tapped, a mat 
was present. After trees have been dead 
for some time, of course, the entire trunk 
surface may produce a hollow sound. 
However, on trees that have reached this 
stage, few if any new mats will form. 
Many mats can be located merely by find- 
ing cracks in the bark, fig. 2, but these 
cracks are often so narrow that they are 
overlooked. 
Classification of Mycelial Mats 
The fruiting structure of the oak wilt 
fungus as it appears in nature consists of 
a light to dark grayish tan, sparse to dense 
mycelial felt, in the center of which lies a 
thick gelatinous pad. The mycelial felt 
with its central pad are referred to to- 
