Clomazone, an isoxazolane herbicide, was first registered for use in 1986 for pest grasses and
broadleaf weeds. Although the exact mode of action is still unclear, it is well documented that
clomazone causes bleaching of foliar structures; the clomazone metabolite 5-ketoclomazone is
regarded to cause the bleaching and to be the ultimate plant toxicant. Although clomazone
exhibits low mammalian toxicity and is selective towards certain plant species, studies have
shown that it does inhibit AChE and catalase activities. In addition, it has been found to be
highly toxic to aquatic invertebrates, in particular mysid shrimp.