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EXTOXNET PIP-NICOSULFURON Page 1 of EXTOXNET 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 5/95 NICOSULFURON TRADE OR OTHER NAMES: Trade names for products containing nicosulfuron include Accent, Challenger, Dasul, Lama, Milagro, Mistral, Motivel, Nisshin and Sanson (37, 38). REGULATORY STATUS: Nicosulfuron is a general use pesticide with a toxicity classification of IV (relatively non- toxic). Check with specific state regulations for local restrictions which may apply. Products containing nicosulf Iron mus bear the signal word "Caution" on their label (37). INTRODUCTION:Nicosulfuron is a member of the sulfonylurea family of herbicides. It controls weeds by inhibiting the plant enzyme acetolactate synthase, or ALS. This enzyme is not found in livestock, fish or man. Inhibiting the ALS enzyme system blocks the production of the amino acids, valine and isoleucine, essential building blocks of proteins and other plant components (46).Nicosulfuron is applied postemergence with a non-ionic surfactant when weeds are 4-12 inches tall and actively growing. Rain within two hours of application will not decrease the effectiveness(38). Nicosulfuron is used for control of weeds such as Johnsongrass, quackgrass, foxtails, shattercane,panicums, bamyardgrass, sandbur,pigweed, morningglory and others. Crops include field corn and popcorn(46, 38, 50, 51). Nicosulfuron comes in a 75% water dispersible granule formulation. It may be tank mixed with a limited number of other compounds (46, 38, 50, 51). TOXICOLOGICAL EFFECTS • Acute Toxicity: The amount of a chemical that is lethal to one-half(50%)of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The toxicity of nicosulfuron varies. The acute oral LD50 for technical nicosulfuron was reported to be>5,000 mg/kg body weight(toxicity category IV). The acute dermal LD50 was>2,000 mg/kg body weight(toxicity category IV). The acute inhalation LC50 was>5.9 mg/L(toxicity category III). Primary dermal irritation testing showed nicosulfuron to be a non-irritant and a non-sensitizer (toxicity category IV). The primary eye irritation testing showed nicosulfuron to be a moderate irritant(toxicity category III) (46, 37, 48, 50, 51). • Chronic Toxicity: A ninety-day subchronic toxicity study reported no effects up to 20,000 ppm for rats and dogs and 300 ppm for mice (46). In 28-day feeding trials to mice and rats, no adverse effects were noted up to 30 gm/kg (48, 51). In a 1-year feeding study, dogs were treated with nicosulfuron at doses of 0, 250, 5000,or 20000 ppm. The systemic NOEL of 5000 ppm for males and 20,000 ppm for females (or 147 and 587 mg/kg body weight/day, respectively) is based on a decrease in body weight gains and a concomitant increase in relative liver and kidney http://extoxnet.orst.edu/pips/nicosulf.htm 7/1/200(