414 
Journal of Agricultural Research 
Vol. XXV, No. io> 
block of 53 Rome trees near Paoli, 27 contained blotch cankers. In all 
these cases the evidence pointed toward introduction of blotch with the 
nursery stock. 
The cankers in young trees were always in the lower parts of the tree. 
In trees planted in 1917 none were over 6 feet from the ground, but in 
trees planted in 1915 some cankers occurred considerably higher. 
CANKERS ON NURSERY STOCK 
M’Cormack (11, p. 755) in 1910 reported blotch on nursery stock in 
Indiana, and Melhus, as reported by Curtiss and Brown (4, p. jo), 
in Iowa has recently found first-year apple grafts seriously injured 
by blotch and has also found seedlings infected. The occurrence 
of 159 blotch cankers on the first-year scion wood of 10 trees received 
from an Oklahoma nursery has been mentioned. Old ankers were also 
present on the stock below the graft (PI. 2, C). Blotch cankers 
have been found on 1-year-old Benoni trees in a nursery row and 
also on the trees from which the Benoni buds were obtained. Cankers 
have been found in great abundance on apple seedlings imported 
from Kansas for budding purposes. After these were budded, cankers 
occurred both above and below the inserted buds (PI. 2, A, B) and even 
on the underground root-bearing portions of the stem. 
Nurserymen should guard against blotch by rejecting infected seed¬ 
lings, and by taking bud-sticks only from sprayed or blotch-free trees, 
because of the danger of the presence of invisible leaf-scar infection about 
the buds. The nursery row affords ideal conditions for the spread of a 
water-disseminated fungus such as this, and nurserymen and seedling 
growers should apply the blotch sprays annually. 
Undoubtedly blotch is carried far and wide and introduced into young 
orchards with the nursery stock and, as Anderson (1; 3, p. 389) has ad¬ 
vised, orchardists should reject shipments containing infected trees. 
CANKER ERADICATION IN YOUNG ORCHARDS 
The facts presented relative to the presence of blotch on nursery stock 
and on scattered trees in young orchards, as well as the greater incidence 
of cankers in the lower parts of the trees and the constant differences in 
severity of the disease in individual trees, assist one in interpreting the 
progress of the disease in an orchard. Starting with the trees which were 
originally infected in the nursery, it would seem that the disease slowly 
progresses upward by the splashing of spores from the older cankers to 
leaves higher up until by the time the tree comes into bearing, there are 
cankers high enough to provide a “cone’ 7 of drip and splash infection 
inclusive of most of the tree. Even though considerable tree-to-tree 
spread of infection occurs in old orchards, this appears to be uncommon 
while the trees are young and widely separated, and, to a certain extent, 
each tree continues to present a more or less independent pathological 
picture in which the severity of the disease depends upon the early pres¬ 
ence of cankers and their subsequent rate of multiplication. Further¬ 
more there would seem to be little, if any, dissemination from one orchard 
to another. 
On the basis of this theory, the elimination of the disease from a 
young orchard should greatly reduce, if not entirely obviate, the future 
blotch menace in that orchard. Such a result may be accomplished, it 
is believed, by two measures, the annual application of the blotch sprays 
