INVESTIGATIONS OF POTATO WART. 
15 
Table 4. — Varieties of tomatoes found to be susceptible by planting in infested soil 
in the field. 
[Explanation.— The plus mark (+) indicates 
susceptibility; a blank (- 
-) indicates no test.] 
1919 
Number of plants. 
Variety. 
1919 
Number of plants. 
Variety. 
1920 
1921 
1922 
1920 
1921 
1922 
• 1 d 
a o 
o s 
a 
I 
o 
d 
*3 
o 
O 
•6 
1 
el 
d 
£ 
o 
o 
«2 
a 
d 
1 
o 
T3 
I 
a 
d 
* 
o 
O 
© 
•2 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
6 6 
4 4 
15 
7 
17 
14 
13 
2 


2 
2 
Matchless 
— 
4 
6 
6 
6 
3 
6 
5 
2 
1 
2 
4 
3 
6 
4 
4 
2 
6 
18 
6 
10 
7 
5 
4 
3 
Carter's Sunrise 
Early Detroit 
4 
1 
Michigan Early 
— 
Rock 
5 
4 
4 
San JoseCanner — 
Stone 

n 
Maine's New Im- 
perial 
Trucker's Favorite. 
Crackerjack 
1 1 
3 
Dwarf Champion... 
Duke of York 
6 
Acme 
i 
6 
12 
4 
6 
5 
4 
4 
? 
? 
Bonny Best 
Red Cherry 
Yellow Cherry 
i 
i 
Globe 
i 
i Test with seedlings only. 
In 1921 about 85 varieties of tomatoes were grown, but owing 
to the early maturity of the vines brought about by hot weather and 
Sep tori a leaf -spot and also owing to very light infestation of the soil, 
only a few plants developed wart infection. In 1922 certain varieties, 
including some not hitherto tested, were grown in well-infested soil 
or were subjected to experimental inoculation. The observation 
that tomatoes may become infected at an early stage of growth was 
confirmed, and additional evidence was obtained that plants nearing 
maturity are in general more susceptible. It appears from the 
results of field tests during four years that the precise conditions 
requisite for the infection of tomatoes can be elucidated only by 
experimental inoculation in the greenhouse with all factors subject 
to control. All the trials with tomatoes to date have not given a 
definite answer to the question whether immune varieties comparable 
to immune potatoes really exist. This is a point of much scientific 
interest. 
The statement may be ventured, however, that the tomato has not 
been found to possess such significance as a host plant in the Freeland 
area as to require special consideration in the potato-wart quarantine. 
SUMMARY. 
A number of American varieties of potatoes have been shown to 
be immune to wart caused by Synchytrium endobioticum (Sehilb.) 
Perc. This conclusion is based upon tests extending from one to 
four years in which such varieties remained free from wart infection 
when grown in heavily infested soil in which susceptible varieties 
were generally and severely infected. 
The varieties which have thus proved to be immune are: Early 
Eureka, Early Petoskey, First Early, Cordon's Early Snowflake, 
Flourball and Irish Cobbler, belonging to the Cobbler group; Early 
