APPLE BLOTCH AND ITS CONTROL. 9 
RELATIVE SUSCEPTIBILITY OF APPLE VARIETIES. 
The list of susceptible, moderately susceptible, and resistant vari- 
eties shown in Table II is based on the publications of Scott and 
Rorer and of Lewis and upon the writer’s own observations. It 
often occurs that a variety which is quite resistant and which has no 
twig cankers of its own will show some infections on the fruit if it is 
growing in close proximity to a badly infected variety. 
TABLE II.—List of apple varieties, showing their relative susceptibility to blotch 
infection. 
Very susceptible. Moderately affected. 
Resistant varieties. 
Varieties. Varieties. Varieties. Varieties. 
Missouri. Gano. Oldenburg. McAfee. Winesap. 
Ben Davis. Domine. Benoni. Ralls. Jonathan. 
Northwestern. Huntsman. Arkansas. Yellow Bellflower. | York Imperial. 
Limbertwig. White Pearmain. Bradford. Northern Spy. Givens. 
Maiden Blush. Smith. Ingram. Stayman Winesap. 
Lawver. Tolman. Collins. Fink. 
Shockley. Fameuse. Rambo. Minkler. 
Clayton. Wagener. Golden Russet. Wealthy. 
Willow. Gilpin. Grimes. Rome Beauty. 
Arkansas Black. Yellow Newtown. 
REMEDIAL MEASURES. 
Under ordinary conditions blotch is controlled rather easily by 
spraying, but under conditions of severe infection the spraying 
must be done with great promptness and thoroughness. In mild 
cases control is accomplished by spraying with lime-sulphur solution 
(82° to 34° Baumé) diluted at the rate of 14 gallons to 50 gallons of 
water (or homemade lime-sulphur solution diluted to equal strength), 
but under conditions of severe infection lime-sulphur solution is not 
efficient. Under such conditions control is attained through the use 
of Bordeaux mixture containing 3 pounds of bluestone (copper sul- 
phate) and 4 pounds of lime to 50 gallons of water. Where lime- 
sulphur gives adequate control it should be used, as it is less likely 
to injure the fruit and foliage than Bordeaux mixture. The first 
spraying for the control of this disease should be finished three weeks 
after the blossom petals have fallen, the second should occur three 
weeks later, and the third about 9 or 10 weeks after the petals fall. 
By thorough spraying for three or four years, the number of 
twig cankers will be greatly reduced, making control much easier. 
The old cankers will die out after that length of time, and the coat- 
ing of spray on the young twigs will prevent the formation of new 
ones. 
In this way Mr. Leslie Pierce, of the Bureau of Plant Industry, 
and the writer greatly lessened the number of twig cankers and in- 
creased the ease of control in an orchard in northwestern Arkansas 
during 1913, 1914, and 1915. 
