412 
Journal of Agricultural Research 
Vol. XXV, No. xo 
Table VII .—Spray control of petiole infection , Northwestern variety , IQ 22 
Tree. 
2, 4, and 6 weeks’ spray. 
Petiole infection. 
Number 
examined. 
Percentage 
infected. 
4R1. 
None. 
I, 082 
1,017 
1,230 
U 9 
I, 141 
1, 120 
995 
1, 042 
80 
88 
31 
12 
37 
9 
46 
45 
cRi. 
.do. 
2R2. 
Bordeaux 4—6—50. 
?Ri. 
. do. 
2Rc. 
Bordeaux 2—4—<0. 
2R7. 
. do. 
2R6. 
Rime sulphur i°. . 
. do. 
O * * •*••**• •**♦*•* 
Despite the poor control with Bordeaux, its superiority over lime sul¬ 
phur is apparent, and the equal effectiveness of the weaker strength is 
again manifest. Results obtained on Oldenburg fruit in southern Indiana 
proved that blotch infection started prior to two weeks after petal-fall 
in 1922 and proved the necessity of an earlier blotch spray in seasons 
such as 1922, when the blossoming period is prolonged and petal-fall 
occurs late. 
The results presented above show that the Bordeaux sprays which are 
effective against fruit infection likewise prevent petiole infection, and as a 
consequence prevent twig infection and canker formation. In this 
capacity, lime sulphur is not as effective as Bordeaux, but a weaker 
Bordeaux seems as satisfactory as the standard strength. Under cer¬ 
tain conditions an additional spray earlier than two weeks after petal- 
fall is necessary. 
Scott and Rorer (15), Roberts ( 12 ), and others have noted that the 
sprays which prevent fruit infection also prevent canker formation to a 
certain degree. These results show how this is brought about and em¬ 
phasize the necessity of spraying every year, regardless of crop, as 
Anderson has urged (2, p. 26; 3 , p. 383), in order to prevent petiole 
infection and consequent canker formation. Owing to the longevity of 
the fungus in the cankers, it is probable that it will be necessary to spray 
continuously for at least seven or eight years to eradicate the fungus 
from the tree, and one year omitted will result in a crop of new cankers 
that will necessitate starting the whole campaign over. 
DISTRIBUTION OF CANKERS IN ODD ORCHARDS 
While a large number of varieties are susceptible to fruit infection, 
fewer are subject to abundant canker formation and the latter varieties 
are especially important as harborers and carriers of the disease. North¬ 
western and Oldenburg are conspicuous examples of this class in Indiana, 
and also in Illinois according to Anderson (1). Among the very suscep¬ 
tible varieties, Benoni, Akin, Missouri, Mann, and Willow are more sub¬ 
ject to canker formation than Ben Davis and Stark. Rome and Trans¬ 
parent seem to be more subject to canker formation than to fruit infec¬ 
tion. Cankers have been noted sparingly on Grimes, Wealthy, Stayman, 
Champion, Gideon, Rambo, and Salome, but have not been noted on 
York, Jonathan, Arkansas, and Winesap, on which varieties occasional 
fruit infection occurs. 
