Benazolin

The Uses of Benazolin

Benazolin is a selective systemic herbicide developed in the 1960s that has growth-regulatory action in susceptible plants. Structurally, it is a benzothiazolacetic acid and is unrelated to the four major groups of synthetic auxins discussed thus far. Benazolin controls a range of annual broadleaf weeds in alfalfa (Medicago sativa), canola (Brassica spp.), cereals, clover (Trifolium spp.), corn (Zea mays), grassland, and flax (Linum usitatissimum), and it has a relatively low persistence in the environment.

Definition

ChEBI: A member of the class of benzothiazoles that is 4-chloro-1,3-benzothiazol-2(3H)-one which is substituted on the nitrogen by a carboxymethyl group and at position 4 by chlorine. A post-emergence herbicide used (generally as a salt or este ) for the control of annual weeds in wheat and oilseed rape. It is not approved for use with the European Union.

Safety Profile

Moderately toxic by ingestion. Anherbicide. When heated to decomposition it emits toxicfumes of SOx, Cl^-, and NOx.

Metabolism

Because benazolin is not degraded by light and is not readily volatilized, the most important factors affecting its persistence in the environment are microbial breakdown and leaching. However, because the microbial breakdown is so rapid, significant leaching may not occur unless the rainfall within a few days of application is large.

Toxicity evaluation

Benazolin is primarily excreted in the urine as N-[2-chloro-6-(methylsulfinyl)phenyl]glycine and N-[N-[2-chloro-6-(methylthio)phenyl]glycinyl]aniline. Acid-labile conjugates of benazolin acid and N-[2-chloro- 6-(methylthio)phenylglycine] are also formed in small amounts. The acute oral LD₅₀ for rat and mice are >5000 mg/kg and >4000 mg/kg, respectively. See Table 21 for a list of toxicological data for benazolin.