2 BULLETIN 1169, U. S. DEPARTMENT OF AGRICULTURE. 
land, Indiana, and Illinois, indicates that this can be done, provided 
the directions for use are carefully followed. 
Beginning with the fall of 1921 and extending through the spring of 
1922, extensive experiments with paradichlorobenzene were conducted 
by the Bureau of Entomology in the peach belt of Georgia on trees 
ranging from | to 6 years of age. At the same time studies were made 
in the laboratory on the effect of temperature and moisture on the rate 
of evaporation of the chemical, in order to obtain results for compar- 
ison with those obtained under orchard conditions. 
This bulletin gives a report of progress rather than specific recom- 
mendations as to the use of paradichlorobenzene on peach trees 
younger than 6 years of age. The results obtained are very favorable 
to the employment of the chemical on young trees. Injury resulted 
only to a few trees in the way of brown lesions in the outer bark 
layers. Nevertheless, final recommendations can not be made until 
additional experimental work is completed. In the meantime peach 
erowers should decide for themselves whether, in view of their indi- 
vidual conditions, they are warranted in adopting the treatment on 
young trees, or whether they should continue the well-known practice 
of worming. 
EXPERIMENTAL RESULTS IN THE FIELD. 
The chief objects of the field experiments were (1) to ascertain | 
what dosages can be used effectively and with safety on young peach 
trees; (2) to note effects from not opening up soil mounds six weeks 
after applying the chemical and to note the effects from allowing the 
crystals to remain around the trees all winter; (3) to determine the 
effectiveness of late fall, winter, and spring applications to peach 
trees. 
The object of the laboratory work was to determine the effect of 
temperature and moisture on the rate of evaporation of paradichloro- 
benzene, and to ascertain what influence these factors have on the 
mortality of the peach borer from the toxic gas. 
FIVE-YEAR-OLD ORCHARD TREES. 
One hundred and twenty-two trees were used in an experiment on 
5-year-old trees. Both long exposures of small doses and short ex- 
osures of large doses were tested. For the long-exposure tests one- 
alf, three-fourths, and 1-ounce doses were applied October 12, 1921. 
The soil was removed and examinations made on groups of five trees 
in each test three, four, and six weeks after the material was applied, 
and on five trees the examination was not made or the soil disturbed 
until the spring of 1922. Some of the trees in the check or untreated 
plat of this experiment were examined for borers six weeks after the 
application was made to the treated trees, and the others the follow- 
ing spring. 
or the short-exposure tests, 14, 2, and 24 ounce doses were 
applied October 20, 1921. The soil was removed and examinations 
made on groups of 5 trees in each test 4, 8, and 12 days later. The 
trees in the check or untreated plat of this experiment were examined 
for borers during the latter part of November. 
Table 1 gives the results on the effectiveness of the various doses of 
paradichiorobenzene at different exposures as used on the 5-year-old 
orchard trees. 
