June, 1955 
Table 9.—Longevity of conidia on mycelial 
mats of Endoconidiophora fagacearum placed 
in dry storage at two centigrade temperatures. 
Ronen Per Cent 
Mar T Days IN GERMINA- 
EMPER- 
No. STORAGE TION OF 
ATURE 
ConrIDIA 
BelOe 8 30 75 
Be So... 16 30 60 
Se 16 150 24 
B= See 16 175 34 
Sp eee 16 205 13 
Soe 16 330 33 
grees and some at 16 degrees temperature, 
and tested at irregular intervals for via- 
bility of conidia and pad cells. 
No viable conidia were found after 30 
days on mats that were stored in moist 
bags. Most of these mats were badly de- 
teriorated and overrun by contaminants. 
One mat, which was stored under dry 
conditions at 16 degrees, continued to 
yield viable spores for 330 days, table 9. 
This mat, from which 3 per cent germina- 
tion of conidia was obtained after 330 
days, was very dry and brittle, and no 
reading could be registered from the wood 
with a Delmhorst Model RC-1 moisture 
detector (accurate to 25 per cent). 
Pad cells did not germinate at any time 
during the storage period. In most in- 
stances the cells were colorless and ap- 
peared to be collapsed, or they had broken 
up into fragments. 
Insect Feeding Tests 
Insects that were found most fre- 
quently associated with Endoconidiophora 
fagacearum in the field were collected, 
identified to species when possible,* and 
tested in the laboratory for their ability 
to destroy the fungus by feeding. My- 
celial mats of E. fagacearum were grown 
on sterilized sticks of oak wood in flasks 
of wheat bran broth in the manner de- 
scribed on page 290. The sticks of oak 
wood bearing the fungus were taken from 
the broth and placed on moist filter paper 
in Petri dishes. Some of the insects that 
had been collected were allowed to feed 
* Identification of all insects was made or arranged for 
by Dr. Milton W. Sanderson, Associate Taxonomist, 
Illinois Natural History Survey. 
Curt: Oak Witt INocuLa 
297 
on this fungus and some on pad material 
alone; some of the pad material was ob- 
tained from naturally occurring mats and 
some from laboratory-grown pads. Pads 
were grown abundantly in the laboratory 
simply by planting the oak wilt fungus on 
wet wheat bran in Petri dishes and incu- 
bating it for approximately 3 weeks at 
temperatures that ranged between 16 and 
25 degrees.t 
The only insects found to feed readily 
and with destructive effect on the my- 
celium and pads were species belonging to 
the family Nitidulidae. The species were 
Carpophilus niger, C. sayi, Carpophilus 
sp. (larvae), Colopterus truncatus, C. 
semitectus, Glischrochilus obtusus, G. 
sanguinolentus, and an unidentified spe- 
cies of Glischrochilus (larvae). Fig. 12 
shows the feeding of Carpophilus larvae 
on the mycelium and pad material of En- 
doconidiophora. The ambrosia beetles, 
Xyloterinus politus, Monarthrum mali, 
and M. fasciatum, and members of the 
order Collembola, or springtails, were ob- 
served feeding on mycelial mats, but their 
effects on the fungus were not macro- 
scopically evident. 
FIELD OBSERVATIONS 
Development of Mats 
During the course of this study, the de- 
cline of trees in each wilt area was fol- 
lowed closely over the 10-month study 
period, October, 1952, through July, 
1953. The rate of decline of a wilt-in- 
fected oak and the length of time required 
for the tree to reach a condition favorable 
for the development of mycelial mats was 
found to be influenced by the place 
and time the wilt started. Wiailt-infected 
trees in the more northern study areas, 
Chicago, Rockford, and Sinnissippi For- 
est, usually were producing mats 1 to 3 
months earlier than trees that wilted at 
approximately the same time in the Pe- 
oria and Havana areas, 125 to 150 miles 
southward. In the two southerly areas, 
the average monthly temperature for the 
10-month period was slightly higher and 
+ A method used for growing mycelial pads of 
Endoconidiophora fagacearum on artificial media was de- 
veloped by E. B. Himelick, Assistant Plant Pathologist, 
Illinois Natural History Survey. 
