Pyrasulfotole is a herbicide used to control broadleaf weeds in what and barley. It is a selective benzoylpyrazolone, pyrazole compound, registered in Canada and Australia in 2004, and the USA in 2007. Bayer patented it in Australia in 2006, and the patent expired in March 2026.
Application Pyrasulfotole is generally sold as an emulsifiable concentrate of 75-230 g/L, or 37.5 g/L in a mixture with bromoxynil. Some pyrasulfotole formulations include mefenpyr-diethyl as a safener. Bayer's patent also covers other safeners: cloquintocet-mexyl and 4-cyclopropylaminocarbonyl-N-(2-methoxybenzoyl)benzenesulfonamide.
Mechanism It acts by one mechanism of action, inhibition of 4-hydroxyphenylpyruvate dioxygenase (HPPD), placing it in the Group H (Australia), Group F2 (global), Group 27 (numeric) HRAC class. An APVMA report claims pyrasulfotole acts by two mechanisms of action: inhibiting "4-hydroxyphenylpyruvate deoxygenase" (sic) (HPPD) and disrupting plant cell growth, with a dual HRAC class of Groups F & I (Australia), though inhibiting HPPD is the MoA of Group H (Group 27), and as of 2026, pyrasulfotole is listed as only as Group H.
Tradenames Formulations of pyrasulfotole have been sold as Galaxy (Nufarm), Marathon (ADAMA), Precept (Bayer), and Pyrasulfotole 80 (4Farmers), and as an active ingredient in a mixture with bromoxynil as Pyra Brom (4Farmers), and Velocity (Bayer).
References
External links Pyrasulfotole in the Pesticide Properties DataBase (PPDB)