Dec. 15, 1923 
Control of Apple Scald 
533 
basis. The scald control secured with the direct applications has been 
approximately in proportion to the amount of oil used and in proportion 
to the inhibition of coloring, but the scald control secured with the oiled 
wrapper has been entirly out of proportion to the amount of oil deposited 
on the apples and out of proportion to the inhibition of color develop¬ 
ment in the skin. The direct application of 0.017 gm. of oil per apple 
has reduced scald from 40.5 per cent to 14.7 per cent (see Table VIII and 
discussion), and the direct application 0.06 gm. per apple has reduced 
the disease to 9.1 per cent; while the use of oiled wrappers with a deposit 
of less than 0.0211 gm. of oil per apple (see Table III and discussion) 
has reduced scald to 0.5 per cent. The results of the various investiga¬ 
tions on scald have shown that the elimination of the last 10 or 15 per 
cent of the disease is far more difficult than similar reductions from higher 
percentages; and it seems impossible to explain the extreme efficiency of 
the oiled wrapper on the basis of the small deposit of oil on the apple. 
The evidence at hand seems to justify the conclusion that the inhibition 
of coloring in the skin of the apple is due to the oil actually deposited 
on it, but that the scald control is determined by the total oil lying in 
close proximity to the apple but not necessarily deposited on it. 
This theory of scald control receives further support from the fact 
that the disease has been greatly reduced on apples that were unwrapped 
or in unoiled wrappers, but adjacent to apples in oiled wrappers, and 
slightly reduced on similar apples that were two or more layers distant 
from the oiled wrappers (Table VI), and also by the fact that apples 
with an unoiled wrapper inside the oiled one and with apparently no 
deposit of oil on the apples have had but little more scald than those 
with the oiled wrapper in direct contact with the skin of the apple. 
CRITICAL PERIODS IN THE DEVELOPMENT OF SCALD 
The oiled wrapper has furnished a convenient means of determining 
the period in the storage season in which the different varieties of apple? 
need the greatest protection against scald. Table IX shows the results 
obtained by applying the oiled wrappers at different times; in some 
cases at picking time and in others several weeks after the apples had 
been placed in storage. 
The results show that it is not essential to scald control that the 
wrappers applied at picking time should remain on the fruit throughout 
the storage season. In one experiment Rome Beauty apples remained 
free from scald when the oiled wrappers were removed at the end of 
4 weeks of storage, and in another they scalded when they were removed 
at the end of 5 weeks but not when removed at the end of 10 week**. 
Stayman Winesap scalded when the oiled wrappers were removed at the 
end of 6 weeks, but remained free from scald when removed at I the 
end of 9 weeks. Winesap remained free from scald when the wrappers 
were removed at the end of 8 weeks, while Grimes Golden scalded badly 
when the wrappers were removed at the end of 9 weeks. 
Oiled wrappers applied during the first month of storage gave as com¬ 
plete scald control on all varieties as those applied at picking time; 
those applied at the end of 8 weeks gave only partial control on Arkansas, 
York Imperial, and Stayman Winesap, while those applied at the end 
of 12 weeks of storage gave complete control on Rome Beauty and 
Winesap. 
