Nov. 12, 1917 
Jonathan-Spot and Scald of Apples 
293 
entirely in harmony with the temperature responses and the cumulative 
nature of the disease. The question of aeration and humidity will be 
more fully discussed in connection with the results on apple-scald. 
EFFECT OF MATURITY OF FRUIT ON JONATHAN-SPOT 
Experiments were made to determine the effect of the maturity of 
fruit upon its susceptibility to Jonathan-spot. Jonathan apples of a 
particular picking and of a particular lot were divided into two classes 
that were as nearly alike as possible as to size of fruit, but one contained 
apples on which the ground color was decidedly more yellow than the 
other. There was usually also a larger blush area on the former than 
on the latter. The method of selec¬ 
tion has been described on page 299. 
The apples of the two lots were 
placed in moist chambers and dis¬ 
tributed at the different temperatures 
already mentioned. The results of 
the experiments are shown in fig¬ 
ures 7 and 8. In figure 7 curve A 
shows the amount of disease devel¬ 
oped on the green fruit and curve B 
the amount on the ripe fruit; in 
figure 8 curve A the disease on the 
green fruit and curve C the disease 
on the ripe fruit under like condi¬ 
tions. Further contrasts may be 
obtained by comparing the weekly 
development of Jonathan-spot on the 
ripe fruit, as shown in figure 3 with 
the weekly development on the green 
fruit, as shown in figure 6. In both 
the sets of experiments and at all 
the different temperatures the green fruit showed a greater suscepti¬ 
bility to Jonathan-spot than the ripe fruit. 
The color of the spots that occurred on the lighter skin surfaces of the 
fruit was a lighter brown than that of the spots on the blush surfaces. 
The green fruit had less color than the ripe and consequently a relatively 
larger percentage of the light-brown spots. No clear-cut distinction 
could be drawn between the two kinds of spots, as the color of the one 
gradually shaded into that of the other, and they were exactly alike in 
other characteristics. 
It is the general opinion of persons who have made orchard observa¬ 
tions on Jonathan-spot that the disease is worst on the ripest fruit. The 
above experiments show that under certain storage conditions green 
fruit is more susceptible to the disease than ripe fruit, but it does not 
TEMPERA TUR£ C£7V T/GRAOC 
Fig. 8.—Graphs showing the effect of maturity 
of fruit and of aeration and humidity on Jona¬ 
than-spot. Graph A shows the amount of dis¬ 
ease developed at the different temperatures on 
the greenest fruit of the particular lot, graph B 
the amount developed on the fruit that was 
somewhat riper, and graphs C and D the 
amount on the ripest fruit. The apples of 
graph D were stored in open containers and 
the others of the experiment in moist cham¬ 
bers. The experiment was started on October 
6, 1916, and the above records were taken seven 
weeks later. See figures 2, 3, 4, and 5. 
