6 
BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. 
Downing (Ormskirk, England, trials, 1919), and Idaho Rural, are 
immune, whereas American Giant and Empire State are readily sus- 
ceptible. In the white-sprout section Carman No. 1, Clyde, Gold 
Coin, Delaware, Dreer Standard, Green Mountain Junior, Norcross, 
Snow, State of Maine, Uncie Sam, and Wee MacGregor are regarded 
by many commercial growers as identical, 9 yet strains grown under 
these names in the tests here described have reacted diversely to this 
disease (Table 1). Similar diversity of reaction is exhibited in the 
Burbank and Early Rose groups. Only extensive testing of numer- 
ous stocks of a given variety obtained from different sources and a 
careful checking of varietal characters to detect differences can 
eliminate such confusion. On the other hand, the Early Ohio, 
Rural New Yorker, and Triumph groups comprise only susceptible 
varieties, while the Cobbler and Peachblow groups are composed 
entirely of immunes. 
Table 1. — Reaction of American and European potato varieties to potato wart. 
[ Explanation .—Column 1: The test data for varieties marked with a star (*) were furnished by R. E. 
Hartman. Column 2: The data given were furnished by William Stuart. The Field Laboratory of 
Plant Pathology, Charlottetown, Prince Edward Island, is abbreviated to Field Laboratory, Prince 
Edward Island. Column 4: > = Numerous. Column 5: The following symbols are used to indicate 
varying degrees of susceptibility or resistance: 0=immune (every plant free from infection in repeated 
trials); ±=slightly susceptible (less than 20 per cent of individual plants in any test infected, weak 
development of warts); -f = moderately susceptible (usually less than 50 per cent of plants infected, 
weak to strong development of warts, depending upon which part of the plant is attacked and the stage 
of growth at infection); + + = very susceptible (all or most of the plants in a test infected, copious develop- 
ment of overgrowths on all susceptible parts, Pis. I to IV). The question mark (?) implies not that the 
conclusion is doubtful in this instance, but that it has not been confirmed by repeated tests.] 
Group and variety. 
Source of seed. 
Years 
tested. 
Tests 
made. 
Wart re- 
action. 
Group I.— Cobbler: 
Cordon's Early Snowflake. . . 
Early Eureka 
Early Petoskey 
First Early 
Irish Cobbler 
Do 
Do 
Do 
New Early Standard 
Group II.— Triumph: 
Bliss Triumph 
Early Prospect 
White Bliss Triumph , 
Group III.— Early Michigan: 
Brown Beauty (known lo- 
cally in Colorado as Bark- 
ley's Prolific). 
Early Harvest 
Early Sunrise 
Early White Albino » 
Ehnola 
Extra Early Sunlight 
White Albino 
Cordon Bros., Rockford, 111 
W. H. Maule, Philadelphia, Pa 
Darling <k Beaham, Petoskey, Mich... 
S. M. Isbel & Co., Jackson, Mich 
H. E. Gero, Rutland, Vt 
I. B. Bradford, Goldenridge, Me 
Wilfrid Boulter, Prince Edward Island 
J. Bolgiano, Baltimore, Md 
Henry A. Dreer (Inc.), Philadelphia, 
Pa. 
F. S. Campbell & Sons, Three Lakes, 
Wis., and others. 
Smith Bros., Auburn, N. Y 
T. W. Wood & Sons, Richmond, Va. . 
C. F. Clark, Greelev, Colo 
Group IV.— Rose: 
Early Rose 
Evergreen 2 
Northern King 
Seneca Beauty (greenhouse 
test). 
Soaudling Rose 
White Rose * 
Woodbury's White Rose 
C. D. Woods, Orono, Me 
Robert Buist Co., Philadelphia, Pa... 
Johnson Seed Co., Leominster, Mass.. 
E. F. Corey, Presque Isle. Me 
T. W. Wood & Sons, Richmond, Va. . 
Johnson Seed Potato Co., Richmond, 
Me. 
; Several sources 
E. V. Hardenburg, Ithaca, N. Y 
Iowa Seed Co., Des Moines, Iowa 
Gurney Seed & Nursery Co., Yankton, 
S. Dak. 
Several sources 
W r esco Seed Co., Rochester, N. Y 
Vaughan's Seed Store, New York City. 
2 
1 

1 
+ 
4 

?, 

2 

3 
+ 
1 
+ 
2 

I 
+ 
> 

?, 

1 
+ 
1 A variety received under this name from Beckert's Seed Store. Pittsburgh, Pa., in 1922 proved to be 
Irish Cobbler and was immune. 
1 Doubtfully referable to Rose group on account of its very late growing habit. 
* The stock grown under this name is not White Rose, but probably Burbank. 
» TOntario. Potato Council.] [Potato varieties decided to be identical] In Potato Mag. 
p. 15. 1918. 
1, no. 7. 
