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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
during the three weeks in October following the paradichlorobenzene 
application was 70.5°. The mean soil temperature for the same period 
in 1922 was 64.9°, and for the same period in 1921 was 63.2°. Soil 
temperatures were not taken in Central Georgia prior to 1921, but by 
comparing the October 1921, 1922 and 1923 mean sun rise to sun set 
soil temperatures with the mean air temperatures for the same period 
and then with the mean air temperatures for October during the last 32 
years, the normal mean sun rise to sun set soil temperature for October 
was found to be about 65°. Therefore, the mean soil temperature 
during October 1923 in Central Georgia was at least 5 degrees above 
normal. 
Moisture and temperature greatly influence the rate of evaporation of 
paradichlorobenzene crystals. The dryer the soil and the higher the 
soil temperature the more rapid is the generation of paradichlorobenzene 
gas from the crystals. Little, if any, gas is given off when the soil 
temperature is below 60° F. A study of the October 1923 climatological 
data for Central Georgia to which I have referred above, revealed the 
fact that the weather conditions were very unusual, and were favorable 
for an exceedingly rapid generation of paradichlorobenzene gas. 
Upon examining the young peach tree four weeks after the application 
for borer mortality and tree injury, the crystals had entirely disappeared 
in most cases, which was unusual, and the condition of the dead larvae 
caused us to conclude that the rapidity of the action from paradichloro¬ 
benzene had been so great during the fall of 1923 that borer mortality 
resulted within two weeks. 
The rapid action from the gas last October brought about by the 
unusual weather conditions, caused more or less injury to young peach 
trees. Rather severe injury resulted to some of the three year old trees 
from the use of the and one ounce dose. The extent of this injury 
cannot be definitely determined until next spring or summer, however, 
at the present time some severe cambium injury has been discerned. 
During the three years that the experiments have been under way 
(including 1923) no injury has resulted from the use of the ounce dose 
around four and five year old peach trees for twenty eight days. Under 
the weather conditions in Central Georgia during October 1923 the one 
ounce dose caused some flecking of the bark layers of four and five year 
old trees, and in a few cases the six weeks exposure of the one ounce 
dose caused some cambium injury to trees of those ages. 
One and two year old trees have shown, during each of the three 
