288 
Journal of Agricultural Research 
Vol. XI, No. 7 
JONATHAN-SPOT 
DESCRIPTION 
Jonathan-spot (19) is a name applied to superficial black or brown 
Spots of the apple that are especially common on the Jonathan variety. 
In the early stages of the disease only the superficial color bearing cells 
are involved, and the spots are seldom more than 2 mm. in diameter. 
Later the spots may enlarge to a diameter of 3 to 5 mm., become slightly 
sunken, and spread down into the tissue of the apples to a considerable 
depth. In the later stages of the disease rot fungi are often present, 
species of Alternaria being particularly common. The spots usually 
occur at lenticels. 
RELATION OF JONATHAN-SPOT TO APPLE ROTS 
Scott and Roberts (19) have pointed out that a apecies of Alternaria 
is often present in late stages of Jonathan-spot, and Cook and Martin (6) 
have found that a species of Alternaria is almost universally associated 
with Jonathan-spot as it occurs in New Jersey. The writers' experiments 
and observations indicate that fungi are not present in the initial stages 
of the disease, but that Jonathan-spots often serve as points of infection 
for species of Alternaria and other apple-rot fungi. In addition to 
repeated observations on this point, inoculation experiments were made 
to determine the influence of Jonathan-spot upon the susceptibility of the 
fruit to rot infection. A box of western Jonathan apples purchased on 
the Washington market were separated into two lots, one affected with 
Jonathan-spot and the other free from it. The apples of the two lots 
were practically alike in size and color. Part of the spot-free apples 
were punctured with a platinum needle, two punctures being made on 
each apple. All of the apples were washed in water that carried a heavy 
suspension of the spores of rot fungi, and the fruit was then stored in 
moist chambers at 15 0 C. The following results were obtained at the 
end of two weeks. 
Tabus I .—Effect of Jonathan-spot on infection by apple rots 
Fungus. 
Condition of apples used. 
Total number of infections on 
apples— 
Sound. 
{ Spotted. 
1 
Punc¬ 
tured. 
With 
Jonathan- 
spot. 
Free from 
Jonathan- 
spot. 
With a 
total of 
eight 
needle 
punctures. 
A Iternaria sp. . 
6 
6 
4 
12 
0 
I 
PeniciUium expansum . 
6 
6 
4 
1 
2 
7 
Sclerotinia cinerea . 
6 
6 
4 
O 
0 
1 
No fungus... 
6 
6 
4 
I 
O 
0 
The results show that apples affected with Jonathan-spot are especially 
susceptible to infection with Alternaria sp. 
