Apr. 15, 1921 
Bacterial Spot of Tomato 
153 
injury, and in the soil germination tests some of these treatments re¬ 
sulted in increased vigor as compared with the untreated controls. 
To test the effectiveness of these treatments, some of the seed, after 
treatment, was rinsed in sterile water rather than tap water and dried. 
Seeds were then planted in agar poured plates. Perfect sterilization 
was obtained only with the mercuric-chlorid treatments, and of these 
the weaker strengths seemed to be as effective as the more concentrated. 
The hot water gave only 24 per cent sterile seed, the 10 per cent for¬ 
maldehyde gave 36 per cent, and the 5 per cent formaldehyde gave 
only 4 per cent. The hot formaldehyde gave only 16 per cent sterile 
seed. Thus the mercuric-chlorid treatments are effective and the 
formaldehyde treatments are not thoroughly effective against the ordi¬ 
nary surface flora of the seed. 
However, tests with the causal organism of bacterial spot in sus¬ 
pension had shown it to be killed by 5 minutes' exposure to 2 per cent, 
5 per cent, and 10 per cent formaldehyde and to mercuric chlorid 1 to 
2,000 and 1 to 4,000. To test the effectiveness of the formaldehyde 
and mercuric-chlorid treatments on inoculated seed, a quantity of seed 
was sterilized in water in the autoclave, dipped in a suspension of the 
organisms, and dried in sterile Petri dishes. Then some of this seed 
was tied up in gauze bags and immersed in the disinfecting solution 5 
minutes, rinsed in sterile water, and dried in Petri dishes. These seeds 
were then tested by planting in agar poured plates, with results as pre¬ 
sented in Table IX. 
Table IX .—Effectiveness of seed disinfection (inoculated seed) 
• 
Treatment (5 minutes). 
Number of 
seeds 
tested. 
Number 
showing 
bacterial 
growth. 
Percentage 
of effec¬ 
tiveness. 
Control, untreated. 
tQ 
AO 
2 per cent formaldehyde. 
60 
8 
87 
5 per cent formaldehyde. 
60 
7 
88 
10 per cent formaldehyde. 
60 
3 
QC 
5 per cent formaldehyde after immersion in 40 per 
yj 
cent alcohol. 
80 
7 
m 
5 per cent formaldehyde after immersion in 10 per 
/ 
cent alcohol... 
Control, untreated. 
80 
IOO 
5 
94 
HgCl 2 , 1: 2,000. 
IOO 
y J 
O 
100 
HgCl 2 , 1: 3,000. 
IOO 
0 
IOO 
HgCl 2 , 1: 4,000. 
IOO 
0 
IOO 
Thus, it is seen that the formaldehyde treatments do not perfectly 
sterilize all the inoculated seed even where perfect wetting is insured by a 
preliminary immersion in alcohol. On the other hand, perfect steriliza¬ 
tion was obtained with mercuric chlorid 1 to 2,000, 1 to 3,000, and 1 to 
4,000. 
