THE CONTROL OF CABBAGE BLACK-LEG. 
21 
Table VIII. — Development of cabbage black-leg in commercial fields planted with 
treated seeds in the Racine, Wis., district in 1918. 
Treatment. 
Field 
No. 
Diseased plants. 
Seed lot. 
Infected. 
Pre- 
vented 
from 
heading. 
Date of 
obser- 
vation. 
No. 2-17 
1:256 formaldehyde, 30 minutes, rinsed 
2 
3 
1 
1 
4 
5 
Per cent. 
87 
99 
99 
74 
37 
83 
Per cent. 
87 
96 
91 
14 
52 
65 
Nov. 2 
No. 3-17 « 
do. . .' ". . . '. 
Do. 
No. 3-17 a 
do... 
No. 4-17 a 
do 
Do. 
No. 5-17 
do. 
Oct 30 
No. 5-17 
do 
Nov. 1 
five fields 
Average, 
79.8 
67.5 
a Treated by seed grower. 
RESULTS IN 1919. 
The observations were continued at Racine in 1919 and were ex- 
tended to the Appleton and Shiocton districts in east-central Wis- 
consin, where certain quantities of the No. 2-18 and No. 3-18 lots of 
seed had been distributed. Most of the seed in all of these sections 
was sown about May 9. Because of the poor showing made with the 
formaldehyde solution in 1918, treatment with a 1:500 solution of 
mercuric chlorid for 30 minutes was recommended for general use 
in the spring of 1919. A small quantity of untreated No. 2-18 seed 
was sown in the Racine district on May 9. As already noted in 
the experiments conducted at Madison, the disease developed first 
and most rapidly from the untreated seed. When the beds at Ra- 
cine were examined on June 12, black-leg had become widespread in 
the plant -ig of untreated No. 2-18 seed. From the treated seed, how- 
ever, very little of the fungus had developed at this date. Most of 
the transplanting was done within the next two weeks, and the 
disease was effectively checked in most fields, as shown by the re- 
sults of a survey at the end of the season (Table IX) . This was un- 
doubtedly due to the fact that the development of primary infec- 
tions was retarded and the number reduced by mercuric-chlorid 
treatment coupled with the fact that only two rainy periods occurred 
during the remainder of the month — one on June 13-16 and the 
other on June 24. (See fig. 1.) 
In one bed under observation, where practically no black-leg was 
noted on June 11, the disease had become widespread by July 1. 
Two plantings were made from this bed, the first (field 1, Table IX) 
about June 12 and the second (field 2, Table IX) about July 2. A 
comparison of the two fields at the end of the season, as given in 
Table IX and illustrated in Plate II, brings out the effect of extensive 
spread of the disease in the seed bed previous to transplanting. In 
