Feb. a4,1923 
Control of Lettuce Drop with Formaldehyde 
649 
Sclerotia of lot 2 (Table III) were taken 12 days after the first sym- 
toms of drop were noticed on the plants; lots 1 and 3 were taken 14 and 
18 days, respectively, after the first symptoms of drop were noticed on 
the plants. Lots 6 and 7 were aspirated for K hour previous to treat¬ 
ment, while lots 8 and 9 were kept moist in soil for 18 days previous to 
treatment. Lots 10 and 11 were air-dried for 18 days previous to treat¬ 
ment, and lots 4 and 5 for 16 and 35 days, respectively. 
Table III .—Effect of formaldehyde on sclerotia 
Treatment. 
Size of 
sclerotia, 
lots of 9. 
[ Number viable in 
control, untreated. 
Number viable after treatment. 
1 
i/j 
00 
0 
.9 
9 
10 
0 
w 
c? 
0 
m 
| 50 min. 
10 
| 90 min. 
8 
0 
M 
VO 
Cl 
1. Formaldehyde, 
I-IOO.. 
Small... 
8 
5 
0 
O 
0 
O 
0 
0 
2. Formaldehyde, 
I-IOO.. 
Large... 
9 
9 
9 
7 
4 
O 
0 
0 
3. Formaldehyde, 
I-IOO.. 
Small... 
5 
6 
2 
0 
0 
0 
O 
0 
O 
4. Formaldehyde, 
I-IOO.. 
Large... 
7 
4 
6 
2 
1 
O 
0 
O 
5. Formaldehyde, 
I-IOO. . 
Large... 
4 
5 
4 
5 
2 
2 
0 
I 
6. Formaldehyde, 
I-IOO.. 
Small... 
7 
6 
9 
4 
1 
O 
O 
7. Formaldehyde, 
I-IOO.. 
Large... 
6 
7 
7 
1 
‘4 
O 
8. Formaldehyde, 
I-IOO. . 
Small... 
7 
0 
0 
0 
0 
O 
O 
0 
9. Formaldehyde, 
I-IOO.. 
Large... 
8 
0 
0 
0 
0 
0 
0 
O 
10. Formaldehyde, 
I—IOO M 
Small... 
7 
6 
4 
2 
0 
O 
O 
O 
0 
11. Formaldehyde, 
I-IOO,. 
Large... 
8 
9 
9 
7 
4 
3 
O 
0 
O 
0 
RELATION OP MOISTURE TO THE ACTION OP FORMALDEHYDE ON 
sclerotia 
Preliminary work showed that the time required to kill the sclerotia 
of this fungus in different concentrations of formaldehyde solution is 
correlated with desiccation. For further study of this phase one lot 
each of large and small sclerotia was kept in the laboratory in a dry 
bottle plugged with cotton, while similar lots were buried in moist 
loam soil. At the end of 18 days the four lots were removed and 
treated with 1-100 formaldehyde solution. Both small and large 
sclerotia kept under moist conditions described above were killed in 
less than 5 minutes (Table III, treatments 8 and 9). Small dry sclerotia 
were killed in 15 to 20 minutes (Table III, treatment 10), while large 
dry sclerotia were killed in 30 to 50 minutes (Table III, treatment 11). 
When the period of air-drying was extended to 35 days, large sclerotia 
were not killed by an exposure of 75 minutes (Table III, treatment 5). 
In all the experiments where sclerotia were stored under moist condi¬ 
tions the formaldehyde solutions were more effective, which, from the 
practical viewpoint, emphasizes the need of keeping the soil thoroughly 
moist from 5 to 10 days before treatment. 
INHIBITORY EFFECT OF FORMALDEHYDE ON CULTURAL GROWTH OF 
s. libertiana 
During the progress of this study it was found that the solutions of 
formaldehyde greatly inhibited subsequent growth on agar of sclerotia 
and mycelium which were not killed during the treatment—that is, 
growth was delayed by the treatment. It appeared that the action of 
