Revised Classification of Herbicides by Site of Action for Weed Resistance Management Strategies¹

Abstract

The classification of herbicides by site of action, published in 1997, has been revised. The classification system uses a numbering system for a herbicide's site of action, chemical family, and common name. Regulatory agencies in the United States and Canada have published labeling guidelines based on the classification to aid in herbicide resistance management.

Control of herbicide-resistant common waterhemp (Amaranthus tuberculatus var. rudis) with pre- and post-emergence herbicides in soybean

“…The differences between the waterhemp populations at Cottam and Petrolia in the level of their control by ALS inhibitors suggest these biotypes may have different target-site mutations, each conferring a different level and pattern of cross-resistance to herbicides from different ALS inhibitor families. There are five different chemical families that inhibit ALS: sulfonylureas (SUs), imidazolinones (IMIs), triazolopyrimidines (TPs), pyrimidinylthiobenzoates (PTBs), and sulfonylaminocarbonyltriazolinones (SCTs) (Tranel and Wright 2002;Mallory-Smith and Retzinger 2003). Cross-resistance among these herbicide families generally follows one of three patterns: (1) resistance to SUs and TPs, (2) resistance to IMIs and PTBs,or (3) resistance to all of these chemical families (Tranel and Wright 2002).…”

Fish Toxicity of Commercial Herbicides Formulated With Glyphosate

“…Its herbicidal action is due to its ability to inhibit 5-enolpyruvylshikimate-3-phosphatesynthase [1], an enzyme involved in the biosynthesis of aromatic amino acids in plants. Although this substance is an acid, it is commonly used as a salt, such as the isopropylamine salt (IPA) of N-(phosphonomethyl) glycine or the glyphosate isopropylamine salt.…”

Biologically effective rate of sulfentrazone applied pre-emergence in soybean

“…Sulfentrazone is a protoporphyrinogen oxidase (PPO) inhibitor herbicide of the triazinone chemical class (Mallory-Smith and Retzinger 2003). Herbicides with this mode of action block synthesis of chlorophyll and heme, which causes sensitive plants to generate high levels of singlet oxygen resulting in necrosis and eventual plant death (Duke et al 1991).…”