Nov. 12, 1917 
Jonathan-Spot and Scald of Apples 
289 
EFFECT OF TEMPERATURE ON JONATHAN-SPOT 
Scott and Roberts (19) found that apples stored in a moderately cool 
basement developed much more Jonathan-spot than similar fruit held in 
commercial cold storage. 
In 1915 and again in 1916 the writers carried out experiments to obtain 
further data in regard to the factors influencing the development of the 
disease. The fruit used in the experiments was shipped by express direct 
from the orchard to the laboratory, so that there was never a delay of 
more than four days after picking before the apples were placed under 
the various storage conditions. The fruit was always carefully sorted so 
that the apples placed at the various temperatures or humidities that 
were to be compared would be as nearly alike as possible in size, color, and 
maturity. This was accomplished by selecting a number of apples 
that were similar in all respects and distributing them one each in the 
containers that were to be placed 
under the different conditions and 
repeating the process until the desired 
number of apples was obtained. All 
the apples were Jonathan and all 
were free from Jonathan-spot at the 
beginning of the experiments. The 
apples used in the experiments re¬ 
ported in figure 1 were from West 
Virginia, those of figure 7 from New 
Jersey, and those used in the other 
experiments from Pennsylvania. The 
apples used in the experiments re¬ 
corded in figure 6 averaged more than 
3 inches in diameter, while those used 
in the other experiments averaged 
about inches in diameter. In the former cases, 8 apples were used 
for each temperature or storage condition and in the latter, 10 to 15 
apples for each condition. 
The results obtained are shown in figures 1 to 8, inclusive. In all the 
figures the perpendiculars show the average number of spots per apple 
and the base lines the centigrade temperature. 1 In some of the experi¬ 
ments (as noted in the figures) a warm laboratory was used for the 25 0 C. 
temperature. This room temperature was not constant and averaged 
less than 25 0 . All the other temperatures were carefully controlled. 
A study of the curves in the different figures shows that the amount of 
Jonathan-spot increased with a rise in temperature up to 20°, but that 
S /O /S 20 2-5 
JO 
Fig . 1 .—Graphs showing the effect of temperature 
on Jonathan-spot at the end of 2,6, and 8 weeks. 
The apples were stored in moist chambers 
with moist filter paper added. The experiment 
was started on November 6, 1915. 
1 Temperature equivalents. 
°C. °F. °C. °F. °C. ®F. 
0=32 I 5 ~ 59 25=77 
5=41 20=68 30=86 
10= 50 
