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18 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE 
SUMMARY. 
Large doses of paradichlorobenzene, ranging from 14 to 24 ounces, 
to which the tree is exposed for 4, 8, or 12 days, are not as effective 
against the peach borer as three-fourths ounce or 1-ounce doses 
with an exposure of from 4 to 6 weeks. 
The cambium layer of all peach trees ranging in age from 1 to 5 
years treated with paradichlorobenzene for experimental purposes 
was uninjured in the summer following the application in the fall. 
Brown lesions were observed in the outer bark leetrs on afew trees, 
however, at a point near which the ring of crystals had been placed. 
No injurious results from not tearmg down the mounds within 
six weeks after making the application to peach trees in Georgia 
could be discerned. 
During a normal fall in Georgia l-ounce doses of paradichloro- 
benzene will entirely spend themselves, leaving little if any odor 
six weeks after the application. 
In Georgia it is not necessary to uncover the base of the older 
trees four to six weeks after applying the chemical. It is advisable, 
however, to use this precaution against tree injury if the fall is 
abnormally cool, or if the material is applied late, or if it is used on 
young trees. 
If the treatment is given to trees 4 years of age or younger, use 
three-fourths ounce doses. For trees 5 years of age and older use 
the 1-ounce dose. 
Spring treatments of paradichlorobenzene in Georgia are not as 
effective against the peach borer as the early fall treatments. Spring 
applications gave a borer mortality of 72.4 per cent, compared 
with from 95 to 100 per cent mortality from using the material in 
middle October. 
Very poor results were obtained in Georgia by applying the 
crystals during late November or ry December. The most 
satisfactory results are obtained in central Georgia by applying the 
chemical October 10. 
In the laboratory 91 to 135 days were required for the evaporation 
of one-half ounce doses of paradichlorobenzene imbedded from 4 to 
6 inches below the soil surface. One-half ounce doses placed on the 
soil surface evaporated in 16 days. One would conclude from this © 
laboratory experiment that the soil mounded on top of the crystals 
to prevent surface washing and to serve as a container for the gas 
should not be deep, as the deeper the crystals from the top of the 
soil the slower the gas will generate. Of course the normal rate of 
evaporation of paradichlorobenzene around peach trees in an 
orchard is much faster than it would be in the laboratory—the 
latter being at a lower temperature. 
Laboratory tests show that the gas is liberated at about the 
same rate in both sandy loam and clay soils. 
Laboratory experiments show that the gas will kill peach-borer 
larvee as far down as 1 foot below the soil level, and under laboratory 
conditions the gas killed all larve at that depth within three weeks. 
The lower the temperature and the higher the moisture content 
-of the soil, the slower is the action of the gas on the borers. 
