| Chemical Abstract Number (CAS #) |
886500
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| Synonyms | Terbutryn |
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1,3,5-Triazine-2,4-diamine, N-(1,1-dimethylethyl)-N'-ethyl-6-(methylthio)- | Prebane | Igran | Short-stop | Clarosan |
| Analytical Method |
EPA Method 619 |
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| Molecular Formula | C10H19N5S |
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| Use | SELECTIVE HERBICIDE FOR CONTROL OF ANNUAL BROADLEAF & GRASS
WEEDS IN WINTER WHEAT, WINTER BARLEY, SORGHUM (USE FOR WHEAT IS
RESTRICTED TO WASHINGTON, OREGON, IDAHO, & UTAH & USE FOR BARLEY IS
RESTRICTED TO WASHINGTON, OREGON & IDAHO). FORMER USE
PREEMERGENCE WEED CONTROL IN SUGARCANE & SUNFLOWERS & IN
MIXTURE WITH TERBUTHYLAZINE ON PEAS & POTATOES; POST-EMERGENCE
WEED CONTROL IN MAIZE; ALSO USED AS CLAROSAN FOR CONTROL OF ALGAE &
SUBMERGED VASCULAR PLANTS IN WATERWAYS, RESERVOIRS & FISH PONDS.
/FORMER USE
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| Apparent Color | WHITE, CRYSTALLINE; Colorless crystals
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| Boiling Point | 154-160 deg C @ 0.06 mm Hg
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| Melting Point | 104 DEG C
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| Molecular Weight | 241.4
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| Sensitivity Data | Some triazines are mildly irritating to skin, eyes, & upper respiratory tract. Miscellaneous
pesticides of low or moderate toxicity
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| Environmental Impact | Terbutryne may be released to the environment via effluents at manufacturing sites and
at points of application where it is employed as a herbicide. The amount of terbutyryne used
annually in the U.S. was estimated in 1985 to be 585,000 pounds. If terbutryne is released to soil,
it will be expected to be slightly mobile to immobile and therefore will not be expected to leach to
groundwater. It may be susceptible to hydrolysis in soil. Terbutryne may be susceptible to
biodegradation based upon half-lives of 2 and 11 weeks in unfumigated and fumigated soil,
respectively. Volatilization from near-surface soil is not expected to be an important removal
mechanism. A decrease of the amount of terbutryne-caused inhibition of perennial ryegrass to
below 20% inhibition of growth occured within 4.5-25 weeks and 25-60 weeks at application
rates of 1 and 4 pounds/acre. The residual activity of terbutryne is reported as being effective
from 3 to 10 weeks depending on rate of application, soil type, and weather. If released to water,
terbutryne will not be expected to bioconcentrate in aquatic organisms or to volatilize. It will be
expected to adsorb to sediment and suspended particulate matter. Sensitized photolysis and
photooxidation with photochemically produced hydroxyl radicals may be an important removal
mechanisms. It may be subject to very slow hydrolysis in water and may be subject to
biodegradation in water based upon its biodegradation in soil. Half-lives of 240 and 180 days have
been reported for degradation of terbutryne in pond and river sediment under static aerobic
conditions (loosely capped flasks), respectively. If terbutryne is released to the atmosphere, it is
expected to exist almost entirely in the particulate phase based upon a reported vapor pressure of
9.6X10-6 mm Hg at 20 deg C. It may be subject to gas-phase reaction with hydroxyl radicals. The
estimated half-life of gas-phase reaction with hydroxyl radicals is 3.1 hr at an atmospheric concn
of 5X10 5 hydroxyl radicals per cu cm. The most probable exposure would be occupational
exposure, which may occur through dermal contact or inhalation at places where terbutryne is
produced or used as a herbicide.
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| Environmental Fate | TERRESTRIAL FATE: Herbicides, like dichlobenil & terbutryn, are reported to persist
in water & bottom sediments from few mo up to 1 yr.
IN JUNE 1978, TERBUTRYN WAS APPLIED TO 2 FARM PONDS (A & C) NEAR
WINNIPEG, CANADA TO GIVE 100 UG/L WATER CONCENTRATIONS. THE
PERSISTENCE OF THE HERBICIDE & ITS DEGRADATION PRODUCTS WAS
MONITORED FOR 61 WK. THE HALF-LIFE RANGED FROM 3 WK IN POND C, WHICH
CONTAINED GROWTHS OF CATTAILS & DUCKWEED TO 30 DAYS IN POND A
WHICH WAS FREE FROM AQUATIC MACROPHYTES. RESIDUES IN SEDIMENT
REACHED MAX OF 1.4 UG/G (DRY WT) IN POND A & 0.5 UG/G IN POND C. MAX
CONCN OF N-DEETHYLATED TERBUTRYNE WERE 14.4 UG/L IN POND A AFTER 61
WK & 0.14 UG/L IN POND C SEDIMENT AFTER 30 WK. MAX CONCN OF
HYDROXY-TERBUTRYNE IN POND C AFTER 7 WK WAS 6.4 UG/L. TERBUTRYN &
ITS N-DEETHYLATED & HYDROXY DERIV REPRESENTED 71, 28, & 1% (EST) OF
TOTAL TERBUTRYN REMAINING IN POND A & 65, 29 & 6% IN POND C, 61 WK
AFTER APPLICATION. AFTER 12 WK RESIDUES IN PLANTS (POND C) ACCOUNTED
FOR 1-4% OF THE HERBICIDE IN THE POND.
DEGRADATION OF LABELED TERBUTRYN WAS INVESTIGATED IN SEDIMENT &
WATER UNDER DIFFERENT REDOX CONDITIONS. TERBUTRYN DEGRADED
SLOWLY IN STATIC AEROBIC SYSTEMS WITH HALF-LIVES OF 240 & 180 DAYS IN
POND & RIVER SEDIMENT, RESPECTIVELY. DEGRADATION PRODUCTS INCLUDED
HYDROXY-TERBUTRYN, TERBUTRYN SULFOXIDE & N-DEETHYL TERBUTRYN.
MAJOR DEGRADATION PRODUCT WAS THE HYDROXY DERIV REPRESENTING
60-70% OF THE EXTRACTABLE RADIOACTIVITY AFTER 515 DAYS INCUBATION.
UNDER NITROGEN AERATION IN RESPIROMETER FLASKS (REDOX POTENTIAL -46
TO 210 MV) DEGRADATION WAS VERY SLOW WITH A HALF-LIFE OF MORE THAN
650 DAYS.
TERRESTRIAL FATE: RESIDUAL ACTIVITY OF TERBUTRYN IS SIMILAR TO THAT
OF PROMETRYN, BEING EFFECTIVE FROM 3-10 WK DEPENDING UPON FACTORS
SUCH AS RATE, SOIL TYPE, & WEATHER.
TERRESTRIAL FATE: LEACHING & LOSS OF TERBUTRYNE BY SURFACE RUNOFF
WATERS WERE MEASURED UNDER SIMULATED RAINFALL CONDITIONS FROM
UNLIMED & LIMED PEAVINE SILT LOAM SOIL. APPLICATION OF 7 CM WATER
PRODUCED 2-14% RUNOFF WATER FROM UNLIMED SOIL & LITTLE (1-3%) OR NO
RUNOFF FROM LIMED SOIL. 98% WAS ADSORBED BY SOIL. THE AMT OF
TERBUTRYNE IN RUNOFF WATER & SEDIMENT FROM SIMULATED SAMPLE 12 HR
AFTER APPLICATION WAS 0.3% OF THAT APPLIED. SOIL TRANSPORT ACCOUNTED
FOR 1-3% OF THE RUNOFF.
TERRESTRIAL FATE: HALF-LIFE OF TERBUTRYN IN POND WATER WAS 20-30
DAYS. IN BOTTOM SEDIMENT, CORRESPONDING VALUE WAS 400 DAYS.
TERRESTRIAL FATE: THE PERSISTENCE OF TERBUTRYNE (1.5-3.0 KG/HA) IN
DIFFERENT SOILS WAS STUDIED. TERBUTRYNE DISAPPEARED MORE RAPIDLY
FROM SANDY SOIL THAN FROM CLAY SOIL & NONE OF THE CMPD WAS
DETECTED 1 YR AFTER APPLICATION. TERBUTRYNE WAS ADSORBED BY SOIL TO
THE DEPTH OF 5 CM.
TERRESTRIAL FATE: If terbutryne is released to soil, it will be expected to be slightly mobile
to immobile and therefore will not be expected to leach to groundwater. It may be susceptible to
hydrolysis in soil(5,6). Terbutryne may be susceptible to biodegradation based upon half-lives of 2
and 11 weeks in unfumigated and fumigated soil, respectively(7). Volatilization from near-surface
soil is not expected to be an important removal mechanism. A decrease of the amount of
terbutryne-caused inhibition of perennial ryegrass to below 20% inhibition of growth occurred
within 4.5-25 weeks and 25-60 weeks at application rates of 1 and 4 pounds/acre(8). The residual
activity of terbutryne is reported as being effective from 3 to 10 weeks depending on rate of
application, soil type, and weather(9).
AQUATIC FATE: If released to water, terbutryne will not be expected to bioconcentrate in
aquatic organisms or to volatilize. It will be expected to adsorb to sediment and suspended
particulate matter(1,2). Sensitized photolysis and photooxidation with photochemically produced
hydroxyl radicals may be important removal mechanisms(3-4). It may be subject to very slow
hydrolysis in water . It may be subject to biodegradation in water based upon its biodegradation
in soil(6). Half-lives of 240 and 180 days have been reported for degradation of terbutryne in
pond and river sediment under static aerobic conditions (loosely capped flasks), respectively(7).
ATMOSPHERIC FATE: If terbutryne is released to the atmosphere, it is expected to exist
almost entirely in the particulate phase based upon a reported vapor pressure of 9.6X10-6 mm
Hg at 20 deg C . It may be subject to a reaction with hydroxyl radicals. Vapor-phase reaction of
terbutryne with photochemically produced hydroxyl radicals has been estimated to be 124.7 cu
cm/molecule-sec at 25 deg C which corresponds to an atmospheric half-life of about 3.1 hr at an
atmospheric concn of 5X10 5 hydroxyl radicals per cu cm .
TERRESTRIAL FATE: THE LONG SOIL PERSISTENCE OF THESE CMPD DOES
CREATE THE PROBLEM OF SOIL CARRY OVER, WHICH CAN DAMAGE
SUCCEEDING CASH CROPS. THEREFORE EXTREME CAUTION MUST BE TAKEN IN
THEIR APPLICATION ON CROPLAND TO AVOID SUCH INJURY TO FOLLOWING
CROPS. TRIAZINES
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| Drinking Water Impact | SURFACE WATER: WATER & SOIL SEDIMENT SAMPLES FROM TAILWATER
PITS USED TO COLLECT IRRIGATION RUNOFF WERE ANALYZED FOR RESIDUES.
RESIDUES OF PROPAZINE, ATRAZINE, CYANAZINE & TERBUTRYN WERE
IDENTIFIED. CONCN OF PESTICIDE RESIDUES IN WATER WERE SMALL ENOUGH
THAT THE WATER COULD BE REUSED TO IRRIGATE EXCEPT FOR A FEW CROPS
SENSITIVE TO SOME PESTICIDES.
GROUNDWATER: Terbutryne was not detected in groundwaters from new wells in the
Northern Italy province of Bergamo which were shown to contain simazine and propazine .
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