416 
Journal of Agricultural Research 
Vol. XXV, No. ia 
In April, 1922, canker eradication was carried out on an extensive 
scale by Mr. Simpson in an orchard containing about a thousand Olden¬ 
burg trees planted in 1917 and sprayed for blotch in 1920, 1921, and 
1922. In November 214 of these trees were examined (PI. 3, C) and it 
was found that more than half of the 152 trees operated upon were free 
from infection. Cankers had been overlooked in 78, or about one-third, 
of the trees and a very few cases of marginal renewal of fungous growth 
were found. However, the great majority of the cankers had been 
removed and one or two repetitions of the process should practically 
eliminate the disease since the sprays have prevented the formation of 
new cankers. 
Other owners of young orchards in the Vincennes region have cut the 
cankers from their trees and the method bids fair to be widely adopted. 
A Kansas orchardist, William Freienmuth (5), recently reported success 
in cutting out blotch cankers in a 20-year-old orchard of Ben Davis and 
Missouri and strongly advocates canker eradication. He began his 
work in the fall of 1919 and employed somewhat the same methods 
advised above except that the wounds were treated with a Bordeaux 
wash. 
It seems advisable to cut out cankers early in the spring because the 
absence of leaves facilitates detection of the cankers and because the 
wounds heal most rapidly at that time. No disinfectant or wound 
dressing has been necessary on young trees. This operation is harmless 
and inexpensive and removes a dangerous source of blotch infection in 
young orchards. 
SUMMARY 
(1) Blotch cankers on bearing wood are usually located at leaf scars. 
On suckers, watersprouts, nursery stock, and seedlings, cankers occur 
at and also between the leaf scars. Cankers also occur at the bases of 
terminal bud scales and at the bases of spurs. 
(2) Cankers at the leaf scars as a rule become visible during April 
and May of the second season in central Indiana. 
(3) Basal petiole lesions are extremely prevalent in badly diseased 
trees. 
(4) Cases have been noted in which the basal petiole lesions visibly 
extended across the abscission layer to the twig tissue. 
(5) Cankers appear at leaf scars to which leaves with basal petiole 
lesions were attached, particularly where the edge of the petiole lesion 
was not more than 2 or 3 mm. from the abscission layer. 
(6) Cultural tests have shown that the fungus from a basal petiole 
lesion grows down inside the petiole to a distance of 2 or 3 mm. and 
even farther and in many cases crosses the abscission layer into the 
twig tissue before the leaf falls. 
(7) Cankers may originate from terminal bud-scale infection, and 
cankers on large limbs about the base of a spur may have developed 
from a canker on that spur. 
(8) In general, the age of the canker is only slightly less* than that of 
the wood in which it is located. The blotch fungus has been found alive 
in the margins of cankers on wood up to 7 and 8 years old and in one 
case on wood 14 years old. 
(9) The blotch sprays which prevent fruit infection also prevent 
petiole infection and as a consequence canker formation. The preva¬ 
lence of cankers is proportional to the amount of previous petiole infection. 
