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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Tebuthiuron

Trade and Other Names: Trade names for tebuthiuron include Brush, Bullet, Bushwacker, EL-103, Graslan, Herbec, Herbic, Perflan, Reclaim, Scrubmaster, Spike, Sprakil, and Tebusan.

Regulatory Status: Tebuthiuron is General Use Herbicide (GUP). It is EPA toxicity class III - slightly toxic. Products containing tebuthiuron must bear the Signal Word CAUTION.

Chemical Class: substituted urea

Introduction: Tebuthiuron is a broad-spectrum herbicide used to control weeds in non-cropland areas, rangelands, rights-of-way, and industrial sites. It is effective on woody and herbaceous plants in grasslands and sugar cane. Weeds that are controlled by tebuthiuron include alfalfa, bluegrasses, chickweed, clover, dock, goldenrod, mullein, etc. Woody plants take a period of 2 to 3 years to be completely controlled.

Tebuthiuron is sprayed or spread dry on the soil surface, as granules or pellets, preferably just before or during the time of active weed growth. It is compatible with other herbicides.

Formulation: Tebuthiuron is sprayed or spread dry on the soil surface, as granules or pellets, preferably just before or during the time of active weed growth.

Toxicological Effects:

• Acute toxicity: Tebuthiuron has moderate to low toxicity in experimental animals when ingested. Reported oral LD50 values for tebuthiuron are 644 mg/kg in rats, 579 mg/kg in mice, 286 mg/kg in rabbits, greater than 200 mg/kg in cats, and greater than 500 mg/kg in dogs [4,8]. Tebuthiuron is of slight to low toxicity by skin exposure. The dermal LD50 for tebuthiuron in rabbits is greater than 200 mg/kg [4]. Neither skin irritation nor general overall intoxication were produced in rabbits that had 200 mg/kg of the material applied to their skin [4,8]. Tebuthiuron did not induce sensitization or allergic reactions when tested on the skin of guinea pigs [4]. Application of 67 mg herbicide in the eyes of rabbits produced short-term conjunctivitis, inflammation of the lining of the eye, but no irritation to other eye parts, the cornea, or the iris [4]. The inhalation by animals of 3.7 mg/L technical tebuthiuron for 4 hours did not cause toxicity.
• Chronic toxicity: Decreases in body weight gain and red-blood cell counts, along with minor effects on the pancreas were seen in rats fed 125 mg/kg/day for 3 months [9]. Exposure of rats to dietary doses of tebuthiuron as high as 80 mg/kg/day for 2 years was well tolerated, with no indication of cumulative toxicity or serious effects [4]. Similarly, no toxic effects were observed in mice exposed to doses as high as 200 mg/kg/day for most of their lifetime, or in dogs given doses of 25 mg/kg/day for 1 year [4].
• Reproductive effects: The reproductive capacity of rats fed dietary concentrations of tebuthiuron as high as 56 mg/kg/day was unimpaired through three successive generations, and no abnormalities were detected in either parents or offspring [4]. Tebuthiuron administered to pregnant rabbits at doses as high as 25 mg/kg/day, and to rats at doses as high as 180 mg/kg/day, produced no adverse effects on either the mothers or offspring [4]. Based on these data, it is unlikely that tebuthiuron causes reproductive effects.
• Teratogenic effects: No teratogenic effects were observed when rats were fed tebuthiuron at 180 mg/kg/day [4]. A rabbit teratology study was also negative at 25 mg/kg/day, the highest dose tested [4]. Based on these data, it is unlikely that tebuthiuron causes birth defects.
• Mutagenic effects: The Ames mutagenicity asssay for tebuthiuron was negative, as were assays for structural chromosome aberrations using mouse micronuclei [4]. Based on these data, it appears that tebuthiuron is not mutagenic.
• Carcinogenic effects: No tumor related effects were observed in a 2-year rat feeding study at doses up to and including 80 mg/kg/day, the highest dose tested [4]. A 2-year oncogenic study on mice was negative at 200 mg/kg/day, the highest dose tested [4]. These data indicate that tebuthiuron is not carcinogenic.
• Organ toxicity: Damage to the pancreas has been observed in animal studies as a result of exposure to tebuthiuron [36].

• Fate in humans and animals: In rats, rabbits, dogs, mallards, and fish, tebuthiuron is readily absorbed into the bloodstream from the gastrointestinal tract, rapidly metabolized, and then excreted in the urine [4]. Tests indicate that the herbicide is broken down and excreted within 72 hours, primarily as a variety of urinary metabolites [9].

Ecological Effects:

• Effects on birds: Tebuthiuron is practically nontoxic to birds. The reported oral LD50 values are greater than 2500 mg/kg in both mallard ducks and bobwhite quail [4]. A 30-day feeding of 1000 ppm tebuthiuron to hens had no effect [7].

• Effects on aquatic organisms: Tebuthiuron is slightly to practically non-toxic to fish and other aquatic species [4,8]. The reported 96-hour LC50 values are 87 144 mg/L in rainbow trout, and 87 to 112 mg/L in bluegill sunfish [4,8]. The reported 96-hour LC50 values are greater than 160 mg/L in goldfish and fathead minnow [4,8]. The 48-hour LC50 in Daphnia, an aquatic invertebrate, is 225 mg/L [4,8]. The LC50 in fiddler crab is greater than 320 mg/L; the LD50 in pink shrimp is more than 48 mg/L [4,8].
• Effects on other organisms: Tebuthiuron is slightly toxic to bees with a reported contact LD50 of 30 mg/bee [8]. Tebuthiuron may be harmful to non-target plants [4].

Environmental Fate:

• Breakdown in soil and groundwater: Tebuthiuron is highly persistent in soil. Reported field half-lives are from 12 to 15 months in areas with over 40 inches annual rainfall, with longer half-lives expected in drier areas or in soils with high organic matter content [4]. Tebuthiuron is broken down slowly in the soil through microbial degradation. Photodecomposition, or breakdown by sunlight, is negligible, as is volatilization (or evaporation from the soil surface) [4]. It is poorly bound to soil, suggesting high mobility. In field studies, however, little or no lateral movement has been seen in soils with appreciable clay or organic matter content [4]. Neither tebuthiuron nor its degradation products have been detected below the top 24 inches of soil in field studies [4]. It was found in some groundwater samples in Western states (Texas, California, Missouri, Oklahoma, and Washington) at levels up to 3.8 ug/L [4].
• Breakdown in water: No degradation was observed in a 33-day study of photolysis of tebuthiuron in water [4].
• Breakdown in vegetation: Tebuthiuron is readily absorbed through roots and translocated to other plant parts. It produces its effect by inhibiting photosynthesis, the process by which plants receive light from the sun and convert it into energy [4].

Physical Properties:

• Appearance: Tebuthiuron is an off-white to buff-colored crystalline solid with a pungent odor [7].
• Chemical Name: 1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea [7]
• CAS Number: 34014-18-1
• Molecular Weight: 228.31
• Water Solubility: 2500 mg/L at 25 C [7]
• Solubility in Other Solvents: i.s. in benzene and hexane [7]; s.s in chloroform, methanol, acetone, and acetonitrile [7]
• Melting Point: 161.5-164 C (with decomposition) [7]
• Vapor Pressure: 0.27 mPa @ 25 C [7]
• Partition Coefficient: 1.7853 @ 25 C and pH 7 [7]
• Adsorption Coefficient: 80 [19]

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: 0.07 mg/kg/day [31]
• PEL: Not Available
• HA: 0.5 mg/L [36]
• TLV: Not Available

Basic Manufacturer:

DowElanco
9330 Zionsville Road
Indianapolis, IN 46268-1054

• Phone: 317-337-7344
• Emergency: 800-258-3033
  

References:

References for the information in this PIP can be found in Reference List Number 9

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.