Absorption, Translocation, and Metabolism of Sethoxydim in Centipedegrass and Goosegrass

Abstract

<jats:p>Absorption, translocation, and metabolism of foliar-applied <jats:sup>14</jats:sup>C-labeled sethoxydim (<jats:sup>14</jats:sup>C-sethoxydim) in sethoxydim-tolerant centipedegrass <jats:italic>[Eremochloa ophiuroides</jats:italic> (Munro) Hack.] and sethoxydim-sensitive goosegrass <jats:italic>[Eleusine indica</jats:italic> (L.) Gaertn.] were determined. The distribution of <jats:sup>14</jats:sup>C in treated leaves indicated that similar amounts (≈ 3%) were found in the epicuticular wax fraction (chloroform wash) of both species after 6 hours. After 2 hours, 16% of the applied <jats:sup>14</jats:sup>C-sethoxydim was absorbed in the treated leaf by centipedegrass, but only 2% was absorbed by goosegrass. After 2 hours, centipedegrass also readily translocated greater amounts of <jats:sup>14</jats:sup>C than goosegrass (4.3% vs. 0.4%). Six hours after treatment, however, no differences were found in amounts absorbed by the treated leaf and translocated to apical and basal leaves. Because sethoxydim-tolerant centipedegrass absorbed and translocated similar amounts of <jats:sup>14</jats:sup>C compared to the sethoxydim-sensitive goosegrass, these two mechanisms do not appear to be a means of tolerance. The major difference found between the two species was in the metabolism of sethoxydim. After 6 hours, 81% to 98% of the <jats:sup>14</jats:sup>C in goosegrass extracts remained as <jats:sup>14</jats:sup>C-sethoxydim. In contrast, only 1% of the <jats:sup>14</jats:sup>C found in apical leaves, basal leaves, and roots of centipedegrass was identified as <jats:sup>14</jats:sup>C-sethoxydim. These data indicated that differences in tolerance to sethoxydim between these two species were based on metabolism. Chemical name used: 2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2 -cyclohexen-1-one (sethoxydim).</jats:p>

Dose–Response of Newly Established Elephantgrass (Pennisetum purpureum) to Postemergence Herbicides

“…Previous studies have reported , 2% translocation of sethoxydim from treated leaves to roots of bermudagrass, goosegrass [Eleusine indica (L.) Gaertn. ], and centipedegrass [Eremochloa ophiuroides (Munro) Hack] (McCarty et al 1990;Wills 1984), probably explaining our observed results. Elephantgrass survival decreased as the sethoxydim rate increased (Figure 3c).…”

Interactions ofPyricularia setariaewith Herbicides for Control of Green Foxtail (Setaria viridis)

“…Many herbicides need to be absorbed and translocated to active sites. Approximately 16 and 2% of sethoxydim were absorbed by leaves of centipedegrass and goosegrass, respectively, 2 h after application (McCarty et al 1990). When coapplying biocontrol agents with the herbicide in a tank mix, herbicide effects likely are less contributory in early infection stages when plant resistant responses are being mobilized.…”

Effects of Postemergence Herbicides on Centipedegrass Seed Production1

“…Both sethoxydim and clethodim have been widely used in a number of broadleaf crops for selective control of annual and perennial grasses (Derr 1987;Grichar 1991;Johnson and Frans 1991). The mechanism of selectivity of centipedegrass to sethoxydim was shown to be differential metabolism (McCarty et al 1990).…”