258 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
of ten days for the incubation period at that time of the year, paradi¬ 
chlorobenzene applied between October 10-15 in Middle Georgia finds all 
larvae hatched, and since they are small and in shallow galleries a 
control of from ninety-eight to one hundred per cent results provided 
the material is applied strictly according to directions. For best results 
in the Northern or Southern part of the State the dates should vary 
about five days from those found to be most satisfactory for the Central 
Section. 
Late October and November treatments may give fair results. How¬ 
ever, if the late fall should happen to be abnormally cold very poor 
control would result. An effort should be made to apply the material 
shortly after the oviposition period of the insect, so that sufficient action 
from the crystals may be had before the soil temperature becomes too 
cold for the proper generation of the gas. 
Spring applications are not as effective as the early fall applications 
on account of the size of the larvae in the spring and the fact that 
many individuals are in deep galleries by that time. The larger the 
borers and the deeper they are in the galleries, the more difficult it is to 
kill them with paradichlorobenzene gas. Spring applications cannot 
take the place of the early fall treatments, and should only be used where 
for an unavoidable reason the grower was not able to apply the material 
in the fall. Aside from poorer results with spring applications they 
permit the borers to work in the trees unmolested until many are nearly 
full grown. 
Experiments with Paradichlorobenzene 
at Room Temfreatures 
Many experiments were conducted in the laboratory during the three 
years that the field experiments have been under way, including studies 
on the rate of evaporation of paradichlorobenzene under ordinary room 
conditions, mortality of peach borer larvae exposed to paradichloro¬ 
benzene, and the influence of temperature and moisture on the effective¬ 
ness of the material. 
The rate of evaporation around peach trees in an orchard is much 
faster than it would be at room temperature—the latter temperature 
being lower. From ninety-one to one hundred and thirty-five days 
were required for the evaporation of one-half ounce doses of paradi¬ 
chlorobenzene in the laboratory imbedded from four to six inches below 
the soil surface. One-half ounce doses placed on the soil surface evapor¬ 
ated in sixteen days. Therefore, the soil mounded on top of the crystals 
around peach trees to prevent surface washing and to serve as a con- 
