14 
PERSISTENCE OF DDT ON STAYMAN APPLES 
Reported by PD. E. H, Frear, Penn State University 
12 
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Figure 3,--Persistence of DDT on apples. 
TRANSLOCATION OF INSECTICIDES 
Some insecticides are known to enter the sap stream of plants and be translocated 
to parts remote from the point of application, One outstanding example is phorate, which 
may be taken up by the roots and translocated to the aerial parts of plants, where it kills 
insects feeding on them, All degrees of movement in the plant have been observed, rang- 
ing from the above example, to a very slight movement. The actual extent and mechanism 
of movement of the chlorinated hydrocarbon insecticides into the roots, tubers, and 
above-ground parts of plants is actively being studied at present. 
It has been generally assumed that compounds having very low solubility in water 
would not be translocated in plants to any appreciable degree. Some data, many of them 
as yet unpublished, indicate that this may not always be true, San Antonio (16) has analyzed 
carrots grown in soil treated with BHC, using a paper chromatographic procedure, and 
reports the greatest accumulation of residues in the fibrous roots with smaller amounts 
in the edible part, stems, and leaves. Representative data are shown in Table 1. While 
the amount found in stems and leaves was small (0.25 p.p.m.), it does indicate possible 
translocation and the need for further study. Recent biological observations by entomolo- 
gists have also shown the presence of insecticidally effective compounds in the aerial 
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