April, ’24] chandler: paradichlorobenzene 249 
to climate or soil. There are two main types of soil in southern Illinois on 
which most of our orchards are located, the loess soils of the unglaciated 
hill lands, and the gray silt loam of the glaciated prairies. 
Removal of Dirt From Bases of Treated Trees 
In going over the recommendations for the use of P. D. B., I find 
it quite commonly advised to remove the dirt from around the bases of 
treated trees, after a period of from 10 to 14 days. To determine the 
necessity of this procedure w T e left undisturbed until spring a part of the 
trees treated in our first fall’s experimental work in 1920. These trees 
Fig. 7.—Peach tree ready for application of P. D. B. Grass and weeds not 
removed prior to treatment. 
appeared to be just as healthy the following season as those examined 
the fall before. The caution to remove the dirt was not included in our 
recommendations, and as a result this has very rarely been done in 
Illinois. We have, it is estimated, two million peach trees in the com¬ 
mercial orchards of the State. At least a million of these have been 
treated, at some time, with P. D. B., and I have yet to hear of a case in 
which the dirt was removed. This includes such orchards as those 
listed in Table III, which have been treated for 3 and 4 consecutive 
years. 
