Jan. io, 1914 
Twig Blight of Quercus Prinus 
34 i 
INOCULATIONS 
Inoculations were carried on in the greenhouse on Castanea dentata 
(Marsh) Borkh. and on a number of related species of oak —Quercus 
prinus L., Q . minor (Marsh) Sarg., Q. gambelii Nutt., Q. lobata Nee., 
Q. texana Buckl., Q. virginiana Mill., Q. alba L., and Q. rubra L. 
At the time of the first inoculations small potted trees were used, and 
these were mostly in their dormant winter condition. 
The inoculations were made by sterilizing the bark with a mercuric- 
chlorid solution, making an incision through the bark with a sterile 
scalpel, and carefully inserting a portion of the mycelium. The wound 
was then carefully protected by a small portion of sterile cotton. Check 
plants were kept of all inoculations made. 
The first inoculations were made on chestnut on October 24, 1911, as 
no chestnut oak was then available. In seven days the inoculated twigs 
showed a darkened area in both directions from point of infection. 
After one month the twigs were entirely dead from the point of inocula¬ 
tion outward, and the small papillae of the fungus were visible just 
beneath the epidermis. The checks healed normally. 
A pure culture of the fungus was obtained from a portion of a diseased 
twig that was brought into the laboratory. From this culture inocula¬ 
tions were made on November 11, 1911, as follows: 
Four inoculations on Quercus lobata , two by means of an incision in 
the bark and two by simply binding on portions of mycelium in agar 
with sterile cotton; three inoculations on twigs of Castanea dentata; and 
three inoculations on leaves of Q. prinus . One leaf of 0 . prinus was 
inoculated on the upper surface through the wounded epidermis and one 
on the lower; on the other, the mycelium was simply spread over the 
unwounded surface. 
An examination after one week showed inoculated twigs of Quercus 
lobata blackened for about half an inch each way from the point of inocu¬ 
lation; the chestnut was slightly darkened. The wounded leaves of 
Q. prinus , both inoculations and checks, were somewhat yellowed, but 
these subsequently recovered; the unwounded inoculated leaf was 
normal; and all were uninjured by the fungus. After some weeks these 
leaves were brought into the laboratory and careful sections made, but 
no trace of the mycelium could be found in the tissues. 
In all, a total of over 50 inoculations were made in the greenhouse to 
test the susceptibility of different species of oak and to find the time 
when infection most readily takes place. Of these inoculations 50 per 
cent were effective. The twigs darkened and the leaves withered, show¬ 
ing the presence of the fungus. In some the infection did not extend 
more than a few inches from the tip, but in others the whole twig died. 
In but few cases, however, did the fungus make its way into and up the 
main body of the plant. 
