290 
Journal of Agricultural Research 
Vol. XI, No. 7 
the disease made practically no development at 30°. The increase in the 
disease between io° and 15 0 was very striking, and it is of special interest 
to note that in most cases Jonathan-spot was held practically in check at 
5 0 as well as at o°. It was thought possible that the spots might be 
present in an incipient form at the lower temperatures and that they 
would make a rapid development upon 
removal to warmer temperatures, but 
experiments made to test this point 
gave negative results in all cases. 
The failure of the disease to develop 
at 30° indicates that its occurrence can 
not be primarily due to the presence 
of Alternaria sp., as has been sug¬ 
gested by Cook and Martin (6, 7), 
since it has been shown by the writers 
in an earlier publication (3) that 
Alter naria sp. makes a more vigorous 
growth at 30° than at any lower tem¬ 
perature. 
The importance of uniform tem¬ 
perature in the keeping of fruit has often been emphasized. An ex¬ 
periment was made to determine the effect that fluctuations in tem¬ 
perature >vould have upon the development of Jonathan-spot. Apples 
that had been placed in moist chambers were moved back and forth 
from 5 0 to 25 0 at the end of each second day, and the results were 
compared with those obtained at constant temperatures. It was found 
that slightly less disease developed on 
the fruit exposed to the different tem¬ 
peratures than on that kept at the aver¬ 
age temperature of 15 0 . Moving the 
moist chamber to a different tempera¬ 
ture naturally favored an exchange of 
air, and it is possible that this partial 
aeration of the container may have 
had some tendency to decrease the 
disease. However this may have 
been, the results indicated no harmful 
effects from fluctuating temperatures, 
so far as Jonathan-spot was concerned. 
The various experiments make it evident that temperature plays an 
extremely important part in the development of Jonathan-spot. It 
would be impossible to state just whan physiological processes have been 
most concerned in the results, but it is evident that the effects are of a 
cumulative nature. The disease has not usually made much progress 
during the first month of storage, but after that time the number of spots 
Fig. 3.—Graphs showing the effect of tempera¬ 
ture on Jonathan-spot at the end of 4, 6. 8, 
10, and 12 weeks. The apples were well ma¬ 
tured and of the same lot as those of figure 2 
but were stored in open containers in air that 
was gently stirred and that had a relative hu¬ 
midity of 85 to 95 per cent. The experiment 
was started on October 6, 1916. 
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Fig. 2—Graphs showing the effect of tempera¬ 
ture on Jonathan-spot at the end of 4, 5, 6, 7, 
8,10, 12, and 14 weeks. The apples were well 
matured and were stored in moist chambers 
with moist filter paper added. The experi¬ 
ment was started on October 6,19x6. 
