PARADICHLOROBENZENE ON YOUNG PEACH TREES. 9 
when examinations for tree injury were made in July of the same 
ear. Innocase among all the 6-year-old trees treated in late fall or 
in the spring could any injury to the cambium layer be attributed 
to the paradichlorobenzene treatment. 
DISCUSSION. 
The characteristic severe tree injury from the use of paradichloro- 
benzene on young peach trees reported as a result of experimental 
work conducted in more northern latitudes did not occur on any of 
the young trees used for the experimental work in Georgia during 
1921-22. Different climatic conditions which usually cause rapid 
evaporation of the crystals may be responsible, and these are such 
that perhaps it may be possible to use this new treatment on young 
peach trees in Georgia and other Southern States without injury to 
the tree. During a normal fall in central Georgia a 1-ounce dose 
placed around a peach tree will entirely evaporate and leave no traces 
of odor within six weeks. 
In no case among the 558 young peach trees used in the paradi- 
chlorobenzene experimental work in Georgia during 1921-22 could it 
be determined that the cambium layer was injured as a result of the 
toxic action of the gas; but in some instances, previously noted, 
brown lesions were observed in the outer bark layers that could be 
attributed to the gas, since most of the lesions were at a point on the 
trunk near which the crystal rmg had been placed. No special injury 
from leaving the mounds around the trees all winter after making 
the application could be discerned. 
Notes were kept on the quantity of crystals left and the odor present 
when each tree base was opened for examination. These notes re- 
vealed the fact that in the majority of cases 1-ounce doses will entirely 
evaporate and the odor disappear within six weeks during a normal 
October and November in the latitude of Georgia, provided too much 
earth is not placed over the crystals in mounding after applying the 
chemical. ence during a normal fall it is not necessary to uncover 
the base of the trees, especially the old ones, in Georgia and the Gulf 
States six weeks after applying the chemical in order to allow the gas 
to escape, or to remove any remaining crystals. If the fall is cool or 
if the material has been applied very late, this additional precaution 
against injury might be considered and the tree bases uncovered six 
weeks after applying the material. This precaution might also be 
taken if the material is used on young trees. 
Since the three-fourths and 1-ounce doses exposed for four weeks or 
longer resulted in a better control of the peach borer than the large 
doses with short exposures, and since the effect on the trees from 
these long exposures was no greater than from the large doses with 
short exposures, it is suggested that in using paradichlorobenzene on 
peach trees 4 years old or younger in Georgia the three-fourths ounce 
dose be used and allowed to remain around the trees for four weeks. 
As an added precaution against injury on young trees, uncover the 
base of the tree four weeks after applying the chemical. On peach 
trees 5 years old and older in Georgia, use the full 1-ounce dose, and if 
the chemical is applied at the time recommended and if the fall is not 
abnormally cold it will not be necessary to uncover the base of the old 
trees after applying the paradichlorobenzene. 
46631°—23——2 
