Herbicidal efficacy and ecological safety of an allelochemical-based benzothiazine derivative

The development of allelochemical-based herbicides may be of particular value for weed management in cropping systems. However, the action of potential allelochemical-based herbicides on crop selectivity and ecotoxicology needs to be clarified before they can be introduced into cropping systems.

An allelochemical-based 3-(2-chloro-4-ethanesulfonyl)-benzoyl-hydroxy-2- methyl-2H-1,2-benzothiazine-1,1-dioxide, originating from the rice allelochemical tricin, was applied to a paddy system. The benzothiazine derivative could effectively control dominant weeds, while rice was not affected at rates of 75-100 g a.i. ha^-1 . Furthermore, this target compound significantly inhibited the growth of all weeds tested with excellent selectivity for maize; however, it was not safe for soybean. The benzothiazine derivative had no toxic effects on zebrafish and earthworms. The benzothiazine derivative was rapidly degraded in soil with half-lives of 17.51-20.47 days. MiSeq-pyrosequencing revealed relative safety to soil microorganisms at 5 mg kg^-1 of the benzothiazine derivative.

The allelochemical-based benzothiazine derivative at optimal application rates can be recommended to provide satisfactory control of paddy weeds. The benzothiazine derivative with excellent crop selectivity and ecological safety may be further developed for weed management in maize fields. © 2019 Society of Chemical Industry.