Disulfoton
PESTICIDE NAME: Disulfoton
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Trade name(s): Di-Syston
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Manufacturer(s): Mobay Chemical Corp.
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Agric. Chemicals Div.
P.O. Box 4913
Kansas City, Mo. 64120
I. Basic information
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A. Molecular structure: C8H19O2PS3
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B. Chemical name: O,O-Diethyl
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S-(2-(ethylthio)ethyl)phosphorodithioate
C. Derivatives: disulfoton sulfoxide and sulfone
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D. Molecular weight: 274.4 g/mole
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E. Solubility in water: 25 mg/l
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F. Common physical appearance: colorless oil; dark yellowish oil
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G. Oral LD50(rat): 12.5 mg/kg
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H. Pesticide classification: organophosphate insecticide
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I. Restricted use list (N.Y.): yes
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EPA priority pesticide list: no
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J. Crop use: raspberry, blackberry, beans, cabbage, cauliflower,
broccoli, Brussels sprouts, potato, systemic insecticide on
ornamentals, corn
II. Text
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Disulfoton is an organophosphate insecticide used on fruit and
vegetable crops in New York state. It is a restricted-use insecticide
which is widely treated in the scientific literature. Disulfoton is
thought to be of low mobility yet there is evidence that vertical
movement is a factor to be considered. Adsorption is defined by the
Freundlich isotherm and degradation has been shown to be rapid and
complete depending upon the soil type and amount of organic matter
present. The metabolites for disulfoton are the sulfoxide and sulfone.
III. Soil information
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A. Degradation and transformation
Disulfoton is rapidly converted in soil to its mebolites, a
process which is influenced by temperature, moisture content and soil
type. The decline of disulfoton in soil is more rapid under summer
than winter conditions(6). Research varies on the rate of degradation
of disulfoton in soils. One study reported an initial concentration of
disulfoton at 9.80ppm dropping to 0.80ppm at 40d and becoming
undetectable at 60d(9). Stability of the pesticide is influenced by
the presence of organic matter in that increased organic matter and
long periods of time will result in increased degradation rates(3). In
a study with organic soil, 15% of the original disulfoton concentration
was present after 4wks(7). Disulfoton has been found to be
long-lasting in paddy soils due to the fact that it is rapidly
transformed to the metabolites which are insecticidally active(11). In
clay loam upland soils, there was 90% insecticidally active compound at
42d(11).
The half-life of disulfoton has been reported to be 2d in
non-sterile clay loam(11) and 3.5d and 1wk in other soils(2,10). The
sulfoxide and sulfone persisted more than 16d whereas disulfoton was
non-detectable at 8d(2) or 90% gone in 5wks(10). Sulfone breakdown is
the rate-limiting step in degradation of disulfoton to its final
products with the most rapid degradation to sulfone occurring at 20deg
C and 10% soil moisture(2). Maximum sulfoxide has been determined to
occur at 1wk and maximum sulfone at 12wks after application of
disulfoton(10).
The tables below present data concerning degradation and
transformation of disulfoton. The reference is given in parentheses at
the end of each title.
Total residual disulfoton (% of initial application remaining) and
primary specie at various times and under various conditions (11)
Primary Specie
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Soil Tot.resid.14d 3d 14d 28d
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non-sterile cl 84.7% -SO -SO2 -SO2
sterile cl 91.1 Disul Disul Disul
non-sterile sl 80.5 -SO -SO=SO2 -SO2
non-sterile s 76.7 Disul -SO -SO2
non-sterile kaol cl 92.3 Disul Disul -SO=SO2
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Soil moisture and its relation to disulfoton loss(1)
days %loss
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0-irrigated 0
non-irrigated 0
10-irrigated 12.4
non-irrigated 10.4
30-irrigated 70.1
non-irrigated 70.8
45-irrigated 100.0
non-irrigated 99.1
60-irrigated -
non-irrigated 100.0
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B. Adsorption and transport
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Disulfoton is strongly adsorbed(2) and considered to be of low
mobility; however, leaching has occurred into lower temperature zones
where the pesticide is more persistent due to less degradation (from
lowered temperature). A result of this could be increased desorption
and leaching(10). There has beenevidence of more translocation of
disulfoton to upper layers in sandy loam and sand than in silt loam
and paddy soil(11). In sandy loam soil, leaching of metabolites has
been reported with 50% of the residues found below the initial depth
10mo after initial application(10). In a separate study by these same
researchers, the percent of initially applied disulfoton found in the
form of sulfone was found to be: 0-50mma = 7.2%, 50-100mma = 13.2%,
100-150mma = 13.2%, and 150-200mma = 6.3%(10).
The adsorption of disulfoton can be described by a linear
Freundlich isotherm and is influenced by amount of organic matter
present. Desorption becomes more difficult as more insecticide is
removed from the soil(4).
The tables below present data concerning adsorption and transport
of disulfoton in soil. The reference is given in parentheses at the
end of each title.
Adsorption coefficients for disulfoton in two loam soils(4)
Broadbalk loam (18% clay) Time K n
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15 min 20.l 0.88
3 h 19.3 1.04
16 h 24.3 1.00
24 h 21.5 1.00
Woburn loam (7%clay)
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15 min 15.5 0.74
3 h 17.6 0.90
16 h 20.5 0.85
24 h 19.3 0.87
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IV. References (*denotes key reference)
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1.Agnihotri, N.P., H.K. Jain, S.Y. Pandey, R.S. Dewan, A.N. Sexena,
and K.M. Peshwani. 1975. Ind.J.Ent. 37. 68-71.
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*2.Clapp, D.W., D.V. Naylor and G.C. Lewis. 1976. JEQ. 5. 207-10.
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3.El-Rafie, M.S. and Z.H.A. Zidan. 1971.
Bull.Ent.Soc.Egypt.EconServ.V. 159-69.
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*4.Graham-Bryce, I.J. 1967. J.Sci.Food.Agric. 18. 72-7.
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5.Kahn, S.U. Pesticides in the Soil Environment.
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Amsterdam:Elsevier. 1980.
6.Leistra, M. 1978. J.Environ.Sci.Health. B(13). 343-60.
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7.Mathur, S.P., A. Belanger, H.A. Hamilton, S.U. Khan. 1980
Pedobiologia. 20. 237-42.
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8.Singh, K, K.C. Gulati and R.S. Dewan. 1972. Ind.J.Agr.Sci. 42.
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1135-8.
9.Srivastava, K.P., M.G. Jotwani. 1979. J.Ent.Res. 3. 148-56.
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*10.Suett, D.L. 1975. Pestic.Sci. 6. 385-93.
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*11.Takase, I., H. Tsuda and Y. Yoshimoto. 1972.
Pflanzenschutza-Nachrichten. 25. 43-63.
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