280 
(1952) in Pennsylvania found evidence of 
insect and rodent feeding on mycelial mats 
and pads. Himelick et al. (1953) in Llli- 
nois and Campbell & French (1953) in 
Minnesota also reported considerable dam- 
age to the fungus pads by rodents. Birds 
and air currents have received little atten- 
tion as possible agents of transmission. 
The only known practical controls for 
the oak wilt disease at the present time 
consist of interrupting root graft systems 
(Kuntz & Riker 1950a) between healthy 
and infected trees and the practicing of 
sanitation and eradication (Dietz & Bar- 
rett 1946, McNew & Young 1948, 
Young ef al. 1953) in oak wilt areas. 
Hoffman (1952), after investigating oak 
wilt chemotherapy, reported that several 
chemicals showed promise in their ettec- 
tiveness against the pathogen under experi- 
mental conditions. 
FIELD METHODS 
Selection of Trees 
Wilt-infected oak trees used in these 
studies were selected in late September, 
1952. They consisted of 19 red oaks, 
Quercus borealis Michx. f., 9 black oaks, 
Q. velutina Lam., 1 bur oak, Q. macro- 
carpa Michx., and 1 white oak, Q. alba L., 
in five major oak wilt areas in the northern 
half of Illinois where oaks had been dying 
for several years. These areas were in the 
Forest Preserve District of Cook County 
near Chicago; a privately owned 100-acre 
Intinoris NaTuRAL History SurvEY BULLETIN 
Vol. 26, Art. 3 
tract in Ogle County 8 miles south of 
Rockford; Sinnissippi Forest near Ore- 
gon; Detweiller Park at Peoria; and a 
privately owned 50-acre tract, in Mason 
County, 10 miles east of Havana. For 
convenience the study areas will be re- 
ferred to as the Chicago, Rockford, Sin- 
nissippi Forest, Peoria, and Havana areas. 
The total of 30 trees marked for study 
is a relatively small number compared 
with the number of wilted trees in all 
study areas. However, because of the 
thorough examination given each tree se- 
lected and the intensive study made of each 
mat collected or sampled, a larger number 
of trees could not be considered. Mycelial 
mats were collected from a few trees other 
than those marked for study. These were 
designated as miscellaneous mats, and they 
were added to the total number studied. 
Table 1 shows the kinds and diameters 
at breast height of trees that were selected 
for study in each area. The diameters 
ranged from 8 to 40 inches. 
All trees selected for study had been 
naturally infected and had wilted in 1952 
between June 12 and August 25. The in- 
itial examination of these trees showed 
that, in all but three, the trunks were com- 
pletely sound, the only lethal sign being a 
slight brown characteristic streaking in 
the sap wood; the bark was very tight and 
appeared no different from that of healthy 
trees. The three trees mentioned above, 
designated as C-2, R-8, and R-9, were 
more advanced in their decline than the 
other trees. On these the bark was very 
Table 1.—Wilt-killed oak trees chosen for study in five areas of Illinois. Size of trees is 
given in inches d.b.h. 
CHICAGO SINNISSIPPI RockFrorD PEORIA HAVANA 
AREA Forest AREA AREA AREA 
| 
es o - o a3 o = ry s ry 
Fis ge ee Vas a ba I = a fe eet a i fare ee! | 8 | 6 
= Z x= | = en fae” er el a bl 5 B v. = am iY, & 
C-1 | Red | 36 | S-1 |Black}] 12 | R-1 | Red! 20 Pay Red 10 H-1 | Black} 22 
C-2 | Red | 22 | S-2 |Black} 16 | R-2| Red| 24 P-2 | Red 12 H-2 | Black] 20 
C-3 | Red | 10 | S-3 |Black} 12 | R-3 | Red 8 P-3 | Red 10 H-3 | Black] 24 
C-4| Red | 28 | S-4 |Black} 18 | R-4| Red| 14 P-4 | Red 15 H-4 | Black| 20 
C-5 | Bur | 12 | S-5 |Black} 14 | R-5 | Red| 12 P-5 | Red 24 a — —_ 
C-6 |White| 40 | — | — | — | R-6| Red} 10 P-6 | Red 12 — — —_ 
—_ —}|}—-—-|— — | — | R-7| Red} 10 — — — <= —_ —_ 
— — —\— — | R-8| Red| 18 _— — — — —_ _— 
— —. |—-|— | — | — | R-9| Red| 22 — _ — — — —_— 
| 
