the chemist analyzes samples of the product to which application has been made. He then 
plots the results to show the rate of loss. Such curves show the resultant action of 
the many factors influencing loss of the insecticide. Figures 1 and 2 show the curves 
for several chlorinated hydrocarbon insecticides in soil. Figure 3 shows the rate 
of loss of DDT from apples. These curves are typical for the more persistent in- 
secticides, Figure 4, for Diazinon on grapes, illustrates the loss of a less persistent 
insecticide, 
< Plant Industry Station Field Plots 
= 
~ 140 
o 120 ee 
ra a : 
100 qa oases el” Toxaphene 
ny 
5 80 
1 
5 60 “ft Dieldrin 
Oe oreey CO ME © Us rene 
wn” “=. 
£ 40 ==. 
Se 
ral 
a 
(S52 1953 1954 1955 1956 1957 1958 
Years 
BN-10712-x 
Figure 1,--Persistence of toxaphene, dieldrin, and BHC in soil, 
rs Plant Industry Station Field Plots 
Oa 
= 40, ae 
5 120 ete 
ie 
=, 100 pabuheas eee ee 
x 80 
° 
oC 60 Chlordane 
D 
= 
= 
fal 
a 
IS52 1953 1954 [S55 1956 IS 1958 
Years 
BN-10713-X 
Figure 2,--Persistence of aldrin, chlordane, and DDT in soil, 
sia 
