Butenachlor is an obsolete selective chloroacetanilide, chloroacetamide herbicide used to control grasses and broadleaf weeds.Rivard, Linda (2003) "Environmental Fate of Metolachlor", Environmental Monitoring Branch, Department of Pesticide Regulation, Sacramento, California, retrieved 5 February 2026 It was introduced in 1976 and marketed as "Diphenox", by Agro-Kanesho.
Butenachlor's mode of action is to prevent formation of very long chain fatty acids; this makes its HRAC classification Group J (Australia), Group K3 (global) and Group 15 (numeric).
It is stable in acidic, neutral or weakly alkaline conditions; it is unstable in sublight.
Butenachlor is applied at 0.75-1.0 kg/Ha, and usually sold as a pesticide formulation as granules (GR).
Environmental behaviour Butenachlor does not persist in soil; its soil half-life is 2 to 5 days. It is moderately toxic to fish, with a 96-hour LC50 of 0.48 mg/L (0.034 gr/imp. gal). Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242
Safety Butenachlor's acute oral LD50 on rats is 1630 mg/kg (male rats) and 1875 mg/kg (female rates). In mice, it is much less harmful, with an LD50 about 6300 mg/kg. It is slightly irritating to skin and eyes. The inhalatory LC50 for rats is 3.34 mg/L of air over 4 hours. A 90 day NOEL is 25 mg/kg/day for dogs. Butenachlor is non-teratogenic, and has no evident reproductive effects.
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