Sulfonylurea herbicides mammalian toxicity

In summary, the sulfonylureas are new herbicides which exhibit activity at extremely low rates of application and show very low mammalian toxicity. Exceptionally high activity is shown by compounds containing a benzene ring substituted in the ortho position, an unsubstituted sulfonylurea bridge, and a pyrimidine or triazine heterocycle substituted with methyl or methoxy groups. 

Two newer classes of herbicides are active at much lower dosages. The sulfonylureas (11.8)15 are used at 2-4 g/ha. The sulfonylureas have low mammalian toxicity. Only 1.4 oz/acre of the imidazolinones (see 11.8) 16 is needed. 

The ultimate success of this discovery is demonstrated by the fact that there are fourteen commercialized and advanced candidate sulfonylurea herbicides. These compounds are useful in crops such as cereals, soybeans, rice, com, and canola as well as for noncrop use. TTieir low use rates favorable soil half-lives and low mammalian toxicity make them ideal products environmentally. These factors arc discussed in more detail by Brown and Kearney in the following chapter. 

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