146 MANUAL OF FRUIT DISEASES 
developed throughout the growing-season. In the spring the 
pathogene renews activities, thus perpetuating itself from year 
to year. 
Control. 
Spraying is said to offer little hope for the control of rough- 
bark. In most cases it would be a tedious operation to attempt 
eradication of all diseased twigs. On the other hand, the deci- 
sion in this regard must rest with the grower who is especially 
desirous of cultivating the Yellow Newtown in those apple 
regions where the disease is most prevalent. The susceptibility 
of the above-named variety should be borne in mind in contem- 
plation of orchard planting; the experience of the local growers 
of this variety should be the guide in determining whether it 
can be profitably grown in spite of rough-bark. 
REFERENCES 
Roberts, J. W. The rough-bark disease of the Yellow Newtown apple. 
U.S. Agr. Dept. Plant Indus. Bur. Bul. 280: 7-15. 1913. 
Roberts, J. W. A new fungus on the apple. Phytopath. 2: 263-264. 
1912. 
Ozontum Root-Ror 
Caused by Ozonium omnivorum Shear 
The apple and pear particularly are likely to suffer from this 
root-trouble occurring in the South and Southwest. To growers 
in these regions it is probably best known as a cotton disease ; 
however, it affects not only fruit-trees and cotton but also forest- 
trees, vegetables, forage crops and weeds. The range of host- 
plants is practically unlimited, a matter of no mean considera- 
tion from the standpoint of control. 
Symptoms. 
Plants affected by this disease usually show threads of the 
causal fungus on the roots. These threads are at first whitish, 
then dirty-white or brown. If cotton shows the disease, then 
