A TWIG BLIGHT OF QUERCUS PRINUS AND RELATED 
SPECIES 
By Deela E. Ingram, 
Scientific Assistant, Investigations in Forest Pathology , Bureau of Plant Industry 
INTRODUCTION 
A twig blight of the chestnut oak (j Quercus prinus L.) was first reported 
to the Office of Investigations in Forest Pathology on May 31, 1911, by 
Drs. Metcalf and Spaulding, of that office. Specimens were collected 
and sent in from York, Pa. Since that time the disease has been reported 
and diseased specimens have been received from various points through¬ 
out Virginia, West Virginia, Maryland, Pennsylvania, New York, and 
Connecticut. It is not possible at this time to determine definitely 
the exact range of the blight, as sufficient data have not been obtained. 
Nothing is known regarding the origin, age, or directions of distribution 
of the causal fungus, but apparently it will seriously lower the silvi¬ 
cultural status of the chestnut oak. 1 
EFFECT ON HOST 
This blight is primarily a disease of the chestnut oak, but occasionally 
the American chestnut (Castanea dentata (Marsh) Borkh.) and the white 
oak (1 Quercus alba E.) are attacked. Inoculations in the greenhouse 
have proved that a number of other species of oak are also susceptible. 
Trees of all ages and sizes may be attacked, but usually only the 
small branches of the larger trees are affected. In some cases where 
young saplings are attacked the whole tree is killed outright. On the 
affected twigs the leaves wither suddenly without yellowing, gradually 
shrivel, and turn a chocolate brown. This browning of the leaves and 
twigs gives the tree the appearance of the well-known fire-blight of the 
pear and the apple. (PI. XXXVIII.) The fungus often stops at the 
point where the secondary shoots join the main stem, and, as a result, 
the affected twig may rot at the base and fall off. On the diseased twigs 
are numbers of small black pycnidia erumpent through the bark. These 
are sometimes arranged singly and sometimes grouped. Careful sections 
were made of leaves from diseased twigs brought in from the field, but 
no mycelium could be found in the tissues. Cultures were also made, 
but nothing developed. A microscopic examination of a transverse 
section of the wood reveals the presence of abundant mycelium in the 
1 Apparently the only practical method of control for individual trees is cutting back the young twigs 
several inches below the darkened portion. However, under forest conditions no practicable means of 
control is known. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
( 339 ) 
Vol. I, No. 4 
Jan. 10,1914 
