June i, 1921 Celery Seed Treatment for Control of Septoria Blight 
37 i 
this problem. Coons and Levin 1 recommend soaking the seed in warm 
but not hot water for one-half hour and then in a 1 to 1,000 corrosive- 
sublimate solution for one-half hour. Watts 2 states that some growers 
disinfect their seed by placing it for a few minutes in a 1 to 32 copper- 
sulphate solution. The seed should be dried thoroughly after this 
treatment. 
The method devised by the writer is based on tests to determine whether 
the thermal death point of the fungus is lower than that of celery seed. 
Thermal exposures (30 minutes was substituted for the usual 10) were 
made of the pathogene under the following conditions: (a) Spore sus¬ 
pensions in sterile distilled water in test tubes; (b) mycelium 2 weeks 
old in sterile distilled water in test tubes; (c) nutrient agar cultures 2 
weeks old in test tubes. These forms of the fungus were heated in a 
double boiler for 30 minutes to each degree of temperature between 38° 
and 55 0 C. The results showed that only a slight percentage of the 
spores were viable after being heated to 38° and that none retained via¬ 
bility after exposure at 40°. None of the nutrient agar cultures were 
viable at 44 0 , whereas the mycelium in the water blanks was nonviable 
at 45 0 . The higher death point of mycelium in the water blanks is 
probably due to the different densities of the two media. 
The method adopted for determining the thermal death point of the 
seed is as follows: Duplicate lots of 200 seed of Golden Self-blanching 
celery inclosed in cheesecloth bags were heated in water at 40° C. for 30 
minutes, and at each degree between 45 0 and 50°. Untreated controls 
for comparison were used in all cases. The results are shown in Table II. 
Table II. —Percentage of germination of celery seed heated at various temperatures 
Temperature. 
40 
45 
46 
47 
Percentage 0 f 
germination of 
seed. 
Temperature. 
49-5 
51.8 
43 - 3 
44 - 5 
°C. 
48. 
4Q. 
... 
CO... 
V 
Control. 
Percentage of 
germination of 
seed. 
44.O 
40. o 
32. 8 
46.8 
In other words, the temperatures of 40° and 45 0 C. increased germina¬ 
tion 5.8 and 10.7 per cent, respectively, over the control, whereas the 
temperatures from 46° to 49 0 injured germination slightly. At 50° 
germination fell 29.9 per cent below the control. The temperature at 
which celery seed loses its vitality lies somewhere between 50° and 55°. 
From the foregoing it is evident that heating 1- and 2-year-old celery 
seed in water at 48° or 49 0 for 30 minutes eliminates all possibility of 
Septoria infection of seedlings from such seed. 
1 Coons, G. H., and Levin, Ezra, the septoria leap spot disease op celery or celery blight. 
Mich. Agr. Exp. Sta. Spec. Bui. 77, 8 p., 9 fig. 1916. 
> Watts, Ralph L. vegetable gardening, p.302-326. New York. 1912. 
