The effects of flumioxazin in irrigation water were evaluated on four row crop species (corn, cotton, soybean, and wheat) and three ornamental species (begonia, impatiens, and snapdragon). Plants were overhead irrigated one time with flumioxazin at concentrations of 0, 10, 25, 50, 100, 200, 400, 800, 1,600, and 3,200 µg ai/L in water equivalent to 1.27 cm. Ornamental plant tolerances on the basis of a 10% reduction in dry weight (effective concentration 10 [EC10]) were as follows: impatiens (40) < begonia (103) < snapdragon (7,024). The EC10 values of flumioxazin on the basis of dry weight values for row crop species were wheat (35) < corn experiment 1 (53) < cotton (106) < corn experiment 2 (181) < soybean (193). EC10 values for plant height were similar to values for plant dry weight for ornamental and crop species. Snapdragon was the only plant evaluated that was mature at the time of treatment; consequently, all other species were moderately to highly sensitive to irrigation water containing flumioxazin. These data show that flumioxazin can injure and kill immature ornamental and crop species within the potential maximum concentration of 400 µg/L; however, the very short half-life of this herbicide in water with pH 7.0 to 9.0 (ca. 16 h to 17 min) could result in less injury than suggested in this study.
Nomenclature: Flumioxazin; begonia, Begonia × semperflorens-cultorum ‘Senator’; corn, Zea mays L. ‘Garst 8346 LL’; cotton, Gossypium hirsutum L. ‘Stoneville 6611 B2RF’; impatiens, Impatiens wallerana ‘Super Elfin Red’; snapdragon, Antirrhinum majus ‘LaBella Pink’; soybean, Gylcine max (L.) Merr. ‘NG2328R’; wheat, Triticum aestivum L., ‘Wakefield’