Jan. io, 1914 
Twig Blight of Quercus Prinus 
343 
pletely was about 8 feet high and the main trunk about i l /i inches in 
diameter. After two weeks the ends of the twigs withered and the leaves 
dried up. The twigs showed the darkening of the cambium for a dis¬ 
tance of 6 inches from the tip. Sections across the twig also showed 
pustules of the fungus just beneath the bark. After three months the 
pycnidia had broken completely through the bark, spores of both types 
being present in the pycnidium. On June 1, 1912, 20 other inocula¬ 
tions were made in the field by the wounding of the bark and inserting 
a portion of mycelium. Checks were treated in like manner. Of these 
only 7 were effective, as the twigs were by that time older and possibly 
more resistant. In no case were there any large limbs killed, only the 
small branches and tips. 
CULTURE WORK 
The fungus grows well in culture, but does not fruit readily, and then 
only on solid media. Fresh twigs of Quercus alba and 0 . prinus were 
brought in from the field and 
sterilized by wiping with mer- 
curic-chlorid solution and rins¬ 
ing with distilled water. The 
bark was then pricked in several 
places, and portions of agar con¬ 
taining mycelium were spread 
over these portions. These 
were then put in test tubes with 
sufficient moisture. In one 
week discolored areas appeared 
on the twigs, and in three 
weeks the small black pustules 
of the fungus appeared. On 
examination these proved to 
be the Macrophoma stage. 
Twigs of the same species were also used, sterilizing them by the use 
of the autoclave. The growth on these was almost entirely superficial, 
the mycelium completely covering the twigs in a grayish green, felty 
mass. Occasional humps or tufts of mycelium were present in which a 
few pycnidia containing spores of the Macrophoma type were found. After 
six months no further development had taken place. As a medium 
the autoclaved twigs proved to be much inferior to the unheated twigs. 
Of the agars corn meal and prune gave the best vegetative growth 
and were used to the exclusion of others in securing pure cultures and in 
germination studies. Portions of the mycelium were transferred to 
corn-meal flasks or other solid media to secure the formation of pycnidia. 
A number of different kinds of media were used: Potato, prune, beef, 
and corn-meal agars, —15; potato and beef agars, +15; corn-meal and 
Fig. 3. —Diplodia longxspora: Sclerotial bodies formed in 
artificial media. 
