Response of water hyacinth and nontarget emergent plants to foliar applications of bispyribac-sodium alone and combination treatments

• Published in: Journal of aquatic plant management 2015-01, Vol.53, p.7-7
• Main Authors: Mudge, Christopher, Netherland, Michael
• Format: Article
• Language: English
• Subjects: Eleocharis cellulosa; Eleocharis interstincta; Panicum hemitomon; Schoenoplectus californicus
• ISSN: 0146-6623

The recently registered aquatic herbicide bispyribac- sodium (hereafter referred to as bispyribac) is highly efficacious against several noxious aquatic plants including the floating plant water hyacinth [Eichhomia crassipes (Mart.) Solms]. Although this acetolactate synthase-inhibiting her- bicide is effective at low foliar use rates against water hyacinth, the development of injury symptoms and speed of control is slow compared with the herbicides 2,4-D and diquat. Therefore, mesocosm research was conducted to determine if foliar-applied combinations of bispyribac and low rates of the contact herbicides carfentrazone, diquat, endothall, or flumioxazin could improve and increase the speed of control compared with bispyribac applied alone for water hyacinth control. All foliar bispyribac alone and combination treatments containing low rates of contact herbicides reduced water hyacinth dry weight 62 to 74% of the nontreated control 6 wk after treatment (WAT). All other treatments were similar except for the bispyribac plus diquat and bispyribac plus flumioxazin treatments. There was no efficacy advantage of adding a contact herbicide to the tank mix; however, the combination treatments produced faster visual markers and the treatments containing flumioxazin and carfentrazone resulted in no plant regrowth. In addition, the bispyribac combinations were tested for selectivity against the nontarget emergent plants maidencane (Panicum hemitomon Schult.), jointed spikerash [Eleocharis interstincta (Vahl) Roem & J.A. Schult], club-rush (Eleocharis cellulosa Torr.), giant bulrush [Schoenoplectus californicus (C.A. Mey) Palla], and soft-stem bulrush [Schoeno-plectus tabernaemontani (C.C. Gmel.) Palla]. All bispyribac alone and combination treatments reduced jointed spiker- ush and soft-stem bulrush shoot dry weight 37 to 69% and 27 to 42%, respectively, 6 WAT. Despite reductions in jointed spikerash and soft-stem bulrush dry weight, all plants were recovering by the conclusion of the experiment. On the contrary, none of the treatments affected maidencane, club-rash, or giant bulrush. These results indicate that bispyribac alone or in combination with contact herbicides may be a suitable alternative for selectively managing water hyacinth.