Three microcapsule formulations, two starch xanthate formulations, and one commercial formulation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) were evaluated in the greenhouse and field for their relative herbicidal efficacy and persistence. Biological assays with Italian ryegrass (Lolium multiflorum Lam.) revealed significant differences among the formulations in phytotoxicity and persistence. The commercial formulation of trifluralin was generally more phytotoxic than the others to Italian ryegrass sown the week of herbicide application. The two starch xanthate formulations and one microcapsule formulation of trifluralin were generally more phytotoxic and more persistent than the commercial formulation to Italian ryegrass sown from 1 through 19 weeks after herbicide application.
