Jan. 22, 1917 
Temperature Relations of Apple-Rot Fungi 
147 
as great at 25 0 as at 15 0 and Penicillium expansum showing a similar con¬ 
trast between io° and 20°. It was also found that Botrytis produced a 
rot area 25 times as great at 20° as at io° on the Ben Davis and 57 
times as great on the York Imperial. 
The progressive development of the rots is shovjn in figures 5 to 12. 
The curves are based on the diameter of the rot at the various tempera¬ 
tures after the number of weeks indicated. The temperatures are given 
on the base line 
and the diame¬ 
ter of the rots in 
millimeters on 
the perpendicu¬ 
lars. 
It will be ob¬ 
served that in 
general the rate 
of rotting in¬ 
creases with 
time. In some 
cases there ap¬ 
pear to be excep¬ 
tions to this rule, 
but it should be 
remembered that 
the curves are 
plotted on the 
basis of diameter 
and not volume, 
thus giving a de¬ 
creased value to 
the growth rate 
in the larger rots. 
Temperature (^Centigrade) 
It is of particular ^JG, 4-~G ra Ph showing the development of rot on Winesap apples based on 
^ the area instead of the diameter of the rot. 
interest to note 
that the conditions for rapid growth are acquired much more quickly at 
higher temperatures than at the lower ones. At 20° and 25 0 most of the 
fungi became active rot-producing agencies within a week, but as the 
temperatures became lower, longer and longer periods of incubation were 
required. When the fungi had once become well established at the lower 
temperatures, however, the rapidity of the rotting was often most surpris¬ 
ing. Good examples of this necessity of incubation may be seen by con¬ 
trasting the growth of Sphaeropsis malorum at 15 0 and 20° during the first 
week with that of the second, the growth of Sclerotinia cinerea at o° and 
5 0 during the same two weeks, or the growth of Penicillium expansum at 
o° and 5 0 in the first five weeks as compared with that of the last three. 
