Florida Agricultural Experiment Stations


found to be the active ingredient in HETP. The structural
formula of TEPP was believed to be the following (2) :

 SC2\ 0 /OC2H5
 P-0 p

 H5C20 OC2H5
 Parathion is a member of the phosphatic group of insecticides.
 Parathion is the approved common name for the chemical
 O,0-diethyl O-p-nitrophenyl thiophosphate. Its structural for-
 mula is (20):
 0C2H5
 S.P 0 \NO2

 0
 C2H5
 On citrus it proved to be an excellent scalicide. It not only
was a replacement for oil in the control of Florida red scale and
purple scale but also was effective against citrus mealybugs and
cottony cushion scale. Thus, for the first time adequate chemical
control measures of these latter two pests were assured. It fol-
lowed naturally that parathion would be used in large quantities
on citrus in Florida. Since the introduction of parathion upon
the insecticide market numerous other phosphatic compounds
have been made available for testing. One is a combination of
parathion with the dimethyl derivative of parathion, being mar-
keted under the trade name Metacide.
 Another material, available for use on some crops but not
recommended for use on citrus, is known as EPN (ethyl p-nitro-
phenyl thionobenzenephosphonate). Current advertising material
for this compound lists essentially the same precautions for its
use as have been laid down for parathion. Its structural formula
is:
 S

 O- p-- N
 0 C2H5