| Chemical Abstract Number (CAS #) |
732116
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| Synonyms | Phosmet |
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Phosphorodithioic acid, O,O-dimethyl ester, S-ester with
N-(mercaptomethyl)phthalimide | Imidan |
| Analytical Methods |
EPA Method 622.1 |
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EPA Method 8141A |
| Molecular Formula | C11H12NO4PS2 |
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| Use | INSECTICIDE FOR HORNFLIES ON BEEF CATTLE & FOR CATTLE GRUBS; FOR
WEEVILS ON SWEET POTATOES IN STORAGE & ON ALFALFA
/USE ON VARIETY OF CROPS INCL ALFALFA, ALMONDS, APPLES, APRICOTS,
CHERRIES (TART), CITRUS, CORN, COTTON, CRANBERRIES, PECANS,
BLUEBERRIES, GRAPES, NECTARINES, PEACHES, PEARS, PEAS (PACIFIC
NORTHWEST), POTATOES, PLUMS/PRUNES & CERTAIN DECIDUOUS SHADE &
ORNAMENTAL TREES & WOODY EVERGREENS. ACTIVE AGAINST A WIDE RANGE
OF INSECTS SUCH AS ALFALFA WEEVIL, BOLL WEEVIL, CODLING MOTH,
LEAFROLLERS, PLUM CURCULIO, GRAPE BERRYMOTH, ORIENTAL FRUIT MOTH, &
MANY OTHERS.
ALSO REGISTERED FOR USE ON ANIMALS FOR GRUBS, LICE, TICKS, SCABIES,
MITES.
Control of lepidopterous larvae, aphids, psyllids, fruit flies, and spider mites on pome fruit, stone
fruit, citrus fruit, and vines; Colorado beetles on potatoes; boll weevils on cotton; olive moths and
olive thrips on olives; blossom beetles on oilseed rape; leaf beetles and weevils on lucerne;
European corn borers on maize and sorghum; sweet potato weevils on sweet potatoes in storage.
Non-systemic acaricide and insecticide, used on top fruit citrus, grapes, potatoes and in
forestry at rates (0.5-1.0 kg ai/hectare) such that it is safe for a range of predators of mites and
therefore useful in integrated control programs. It is also used to control mites and warble fly of
cattle.
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| Consumption Patterns | 50% AS AN INSECTICIDE FOR WEEVILS ON ALFALFA, ON FRUIT, ON
POTATOES & FOR CATTLE GRUBS & HORN FLIES ON BEEF CATTLE; 50% AS AN
INSECTICIDE FOR WEEVILS ON SWEET POTATOES IN STORAGE, AND ON WOODY
SHRUBS, TREES & VINES (1976)
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| Apparent Color | OFF-WHITE CRYSTALLINE SOLID; Colorless crystals
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| Odor | OFFENSIVE ODOR
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| Melting Point | 71.9 DEG C
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| Molecular Weight | 317.32
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| Density | 1.03 at 20 deg C/4 deg C
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| Environmental Impact | Phosmet's use a non-systemic insecticide releases the compound directly to the
environment through applications in sprays, wettable powders and other routes of application. If
released to the atmosphere, phosmet will degrade rapidly in the vapor-phase by reaction with
photochemically produced hydroxyl radicals (half-life of about 2.6 hr). Particulate-phase phosmet
and aerosols released to air during spray applications of phosmet insecticides will be physically
removed from air by dry and wet deposition. If released to moist soil or water, phosmet can
degrade through aqueous hydrolysis. Hydrolysis half-lives of 4 hr to 3.8 days have been observed
at pHs of 8.0 to 8.3 and temperatures of 4 to 21 deg C; at 20 deg C, hydrolysis half-lives of 13
days (pH 4.5), 7 days (pH 6.1), and 7.1 hr (pH 7.4) have been observed. Insufficient data are
available to access the relative importance of biodegradation in soil or water. A reported Koc
value of 820 suggests low soil mobility; however, phosmet has been detected in leachates
collected near a pesticide manufacturing plant. The US Dept of Agric's Pesticide Properties
Database lists a soil half-life of 19 days. The persistence half-life of phosmet applied to foliage
(alfalfa, peach, bermuda grass, corn, soybean) is reported to vary from 1.2 to 6.5 days.
Occupational exposure occurs through dermal contact and inhalation of sprays, especially to
workers applying the compound as an insecticide. Since phosmet has been detected in U.S. foods,
exposure to the general population may occur through consumption of foods containing phosmet
residues.
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| Environmental Fate | TERRESTRIAL FATE: Since phosmet hydrolyzes readily in water(1-2), it may undergo
hydrolysis in moist soil; hydrolysis increases with alkalinity(1-2), so the degradation rate of
phosmet in soil will probably increase with alkalinity. In one soil persistence study (pH 6.2),
phosmet had a soil half-life of 51-60 days in sealed vials . The US Dept of Agric's Pesticide
Properties Database lists a soil half-life of 19 days for phosmet . The persistence half-life of
phosmet applied to foliage (alfalfa, peach, bermuda grass, corn, soybean) is reported to vary from
1.2 to 6.5 days . The enhanced disappearance from plant leaves may be due to
photodegradation; rapid photolysis on silica and apples has been observed(6). Based upon a Koc
of 820 , phosmet is expected to have low mobility in soil(4,SRC); however, it has been detected
in leachates collected near a pesticide manufacturing plant(7). Insufficient data are available to
assess the relative importance of biodegradation in soil.
AQUATIC FATE: Hydrolysis is a dominant degradation process for phosmet in water; various
studies have observed rapid hydrolysis in alkaline waters(1-4). Hydrolysis half-lives of 4 hr to 3.8
days have been observed at pHs of 8.0 to 8.3 and temperatures of 4 to 21 deg C(1-4); at 20 deg
C, hydrolysis half-lives of 13 days (pH 4.5), 7 days (pH 6.1), and 7.1 hr (pH 7.4) have been
determined(1-2). In one screening study, however, hydrolysis rates of the wettable powder
formulation of commercial phosmet were slower than found in other hydrolysis studies .
Insufficient data are available to assess the relative importance of biodegradation in water.
Volatilization from water and bioconcentration are not expected to be important fate
processes.
ATMOSPHERIC FATE: Based upon a reported vapor pressure of 4.9X10-7 mm Hg at 20-25
deg C , phosmet can exist in both the vapor and particulate-phases in the ambient
atmosphere(2,SRC). It will degrade rapidly in the vapor-phase by reaction with photochemically
produced hydroxyl radicals with an estimated half-life of about 2.6 hr(3,SRC). Particulate-phase
phosmet and aerosols released to air during applications of phosmet insecticides will be physcially
removed from air by dry and wet deposition.
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| Drinking Water Impact | DRINKING WATER: An analysis of Ottawa, Canada tap water (sampling date not
reported) did not detect (detection limit of 1 ng/l) any phosmet .
GROUNDWATER: Phosmet was not detected (detection limit of 5.0 ppb) in ground water
samples collected from 54 wells used for municipal and private water supplies in California .
EFFL: Leachate samples collected near a pesticide manufacturing facility in Barcelona, Spain
during the summer of 1984 contained phosmet concns of 5-10 ppm .
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