|Chemical Abstract Number (CAS #)||
|Synonyms||Phosalone||Phosphorodithioic acid, S-[(6-chloro-2-oxo-3(2H)-benzoxazolyl)methyl] O,O-diethyl
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| SRP: FORMER USE INSECTICIDE, ACARICIDE, MOLLUSCICIDE
Control of chewing and sucking insects and spider mites on pome fruit, stone fruit, citrus fruit,
vines, and ornamentals; Colorado beetles on potatoes; aphids on cereals; aphids, bollworms,
jassids, thrips, and spider mites on cotton; stem borers, leafhoppers, and planthoppers on rice;
thrips and mites on tea; leaf miners on beet; blossom beetles, flea beetles, seed weevils, aphids,
and pod midges on brassicas (including oilseed rape); flower midges on lucerne; seed weevils on
clover; thrips and stem borers on cardamom; sorghum midges.
It is a non-systemic acaricide and insecticide used at 300-600 g ai/100 l against Aphididae,
Contrachelus nenuphar, Cydia pomonella, Cydia molesta, Panonychus species, Psylla pyricola,
Rhagoletis pomonella, Tetranychus species and Tortricidae on deciduous tree fruits; at 400-800
g/hectare on field and market garden crops; against Aphididae, bollworms, jassids, red spider
mites and thrips on cotton; Aphididae and Phthorimaea operculella on potatoes; Meligethes
species and weevils on oilseed rape.
Pests (including lepidopterous, coleopterous, and piercing/sucking pests) on perennial crops,
field crops, vegetables, ornamentals, cotton.
|Consumption Patterns|| ESSENTIALLY 100% AS AN INSECTICIDE FOR FRUITS AND NUTS
|Apparent Color|| CRYSTALS; White; Colorless
|Odor|| SLIGHT GARLIC
|Melting Point|| 47.5-48 DEG C
|Molecular Weight|| 367.80
|Sensitivity Data|| Phosalone is moderately irritating to the skin and eyes.
|Environmental Impact|| Phosalone was a non-systemic acaricide and insecticide recommended for use on fruit
trees, field and market crops, cotton, and potatoes. It is not commercially produced in the United
States. If phosalone is sprayed on crops, its half-life on the plants may range from <1 to 16 days.
Its half-life in soil is 3-7 days. Essentially none of the insecticide is lost by volatilization. In two
soils, 8.5 and 9.9% of phosalone was mineralized in 85 days. Metabolism proceeds by oxidation
of the phosalone to the oxon, cleavage of the O,O-diethyl methyl phosphorodithioate linkage to
form 6-chloro-2-benzoxalinone and ultimately a condensation product that binds tightly to soil.
Phosalone's degradation rate in soil increases with the humous content and pH of the soil. If
released in water, phosalone would adsorb to sediment and particulate matter in the water column
and photolyze in surface layers of water. The rates of other degradative processes in water are
unknown. When phosalone is released into the atmosphere as an aerosol during spraying, it will
be removed by gravitational settling. It will degrade by direct photolysis to produce
phosalone-oxon with an estimated half-life of 86 minutes. Vapor phase phosalone would react
with photochemically produced hydroxyl radicals with an estimated half-life of 2.2 hr. Agricultural
workers may be exposed to phosalone via inhalation during spraying and via dermal contact
during handling or from touching leaves or soil to which the insecticide was applied. The general
population may be exposed to phosalone by ingesting fresh or processed fruits that contain
phosalone residues, especially apples, pears, and grapes.
|Environmental Fate|| TERRESTRIAL FATE: IN SOIL, INITIAL STAGES WERE APPARENTLY SAME
AS IN PLANTS. HOWEVER RED MATERIAL WAS OBSERVED & IDENTIFIED AS
SUBSTITUTED PHENOXAZONE. DISULFIDE FORMED BY OXIDATION OF
PHOSALONE WAS INCORPORATED IN MOIST & FLOODED MATAPEAKE LOAM &
MONMOUTH FINE SANDY LOAM. IT RAPIDLY DISAPPEARED FROM BOTH SOILS.
TERRESTRIAL FATE: If sprayed on plants, phosalone persists for about 14 hr, being
converted into the corresponding phosphorothioate which is rapidly hyrolyzed . Another study
showed that half-life of phosalone applied to apples, grapes and alfalfa was 2.5, 9.9-16.0, and 4.0
days, respectively . When (phenyl-14C) phosalone was uniformly incorporated into moist (75%
field capacity) and flooded Matapeake loam and Monmouth fine sandy loam at 10 ppm and
incubated at 22 deg C, it was found that the half-life in soil was 3-7 days .
TERRESTRIAL FATE: An analysis of soil extracts and volatilized material, indicate that
volatilization was not a major loss mechanism (<0.1%). After 85 days in moist soil, 8.5% and
9.9% of phosalone was converted to CO2, 16.9 and 11.2% were extractable residues, and 74.9
and 79.3% were bound residues. For the flooded soils the values were 0.5 and 2.7%, 11.9 and
11.2%, and 87.6 and 88%, respectively. The bound fraction was primarily associated with the
fulvic acids in soil. Approximately 8% of the extractable 14C remaining in the moist Matapeake
soil after 85 days was phosalone . Based on the products identified in soil, a metabolic pathway
was proposed in which phosalone undergoes extensive binding and condensation in soil, similar to
many aniline-based herbicides. Metabolism proceeds by oxidation of the phosalone to the oxon,
cleavage of the O,O-diethyl methyl phosphorodithioate linkage to form 6-chloro-2-benzoxalinone,
and opening of the heterocyclic ring followed by condensation to form
2-amino-7-chloro-3H-phenoxazin-3-one , the same dimer formed from 4-chloroaniline in
TERRESTRIAL FATE: In a Russian study, only 34.7-41.2% of phosalone remained in the
upper 5 cm of soil 5 days after application . The concn of phosalane in 15 cm sandy loam soil
cores taken from test plots sprayed at 1050 g/ha and 2100 g/ha was 0.293 and 1.18 ppm after
application, 0.165 and 0.493 ppm 6 days after application, and 0.072 and 0.121 ppm 14 days after
application . The half-life of phosalone in soil at the two application rates was 7 and 5.8 days,
respectively . The degradation rate of phosalone in soil increases with the humous content and
pH of the soil .
AQUATIC FATE: If released in water, phosalone would adsorb to sediment and particulate
matter in the water column and photolyze in the surface layers. It would not be expected to
bioconcentrate in aquatic organisms. No information is available concerning the degradation rate
of phosalone in natural waters. Phosalone is relatively stable to hydrolysis in neutral and acid
solution, but hydrolyzes in alkaline solutions to 6-chloro-2-oxobenzoxazole and
diethylphosphorothioic acid .
ATMOSPHERIC FATE: Phosalone will be released into the atmosphere as an aerosol during
spraying and removed by gravitational settling. It will degrade by direct photolysis to produce
phosalone-oxon with an estimated half-life of 86 minutes . The reaction rate for photolysis
depends on the solar irradiance and will therefore be a function of season, latitude, and cloud
cover. Vapor phase phosalone reacts with photochemically-produced hydroxyl radicals
resulting in an estimated half-life of 2.2 hr(2,SRC).
|Drinking Water Impact|| GROUNDWATER: In a survey of farm wells in Ontario, Canada, 103 in 1986 and 76
in 1987, phosalone was not detected in any wells at a detection limit of 0.5 ug/l . However,
phosalone was only used on crops in 2 farms in 1986 and none in 1987 . In a similar survey of
84 farms in Southern Ontario in 1984, phosalone was also not detected . However, only one
farm used phosalone.