Differential Phytotoxicity of Trifluralin and Nitralin

Comparative phytotoxicity of α,α,α -trifluoro-2,6-dinitro- N,N -dipropyl- p -toluidine (trifluralin) and 4-(methylsulfonyl)-2,6-dinitro- N,N -dipropylaniline (nitralin) on several plant species indicated trifluralin was more toxic than nitralin to the shoots while nitralin was more toxic than trifluralin to the roots. An E 0 concentration, defined as that concentration required to prevent seedling emergence, was established for trifluralin on nearly all species assayed. Nitralin did not prevent emergence of any species. Trifluralin was more toxic than nitralin to the shoots of sorghum ( Sorghum bicolor (L.) Moench, var. RS-610) and cucumber ( Cucumis sativus L., var. Wis. SMR-15 and Pioneer) via shoot exposure. Nitralin was more toxic than trifluralin to the roots via root exposure. A comparison of the phytotoxicity through vapor activity showed trifluralin was much more toxic than nitralin.