Troxler et al.: CGA-362622 in nutsedge • 13 Weed Science, 51:13–18. 2003 Absorption, translocation, and metabolism of foliar-applied CGA-362622 in purple and yellow nutsedge (Cyperus rotundus and C. esculentus) Shawn C. Troxler Ian C. Burke Crop Science Department, North Carolina State University, Raleigh, NC 27695-7620 John W. Wilcut Corresponding author. Crop Science Department, North Carolina State University, Raleigh, NC 27695-7620; johnwilcut@ncsu.edu W. David Smith Crop Science Department, North Carolina State University, Raleigh, NC 27695-7620 Jim Burton Horticultural Science Department, North Carolina State University, Raleigh, NC 27695-7609 Studies were conducted to evaluate the absorption, translocation, and metabolism of 14 C–CGA-362622 when foliar-applied to purple and yellow nutsedge. Less than 53% of the herbicide was absorbed after 96 h. Both nutsedge species translocated appreciable amounts of herbicide (30%) out of treated leaves. Translocation was both acropetal and basipetal, with at least 25% transported basipetally. Neither nut- sedge species translocated more than 4% of applied radioactivity to the tubers and roots. Most of the metabolites formed by the nutsedge species were more polar than 14 C–CGA-362622 and averaged 69 and 61% of the radioactivity in purple and yellow nutsedge, respectively. The half-life of CGA-362622 was estimated at 4 h in both purple and yellow nutsedge. Nomenclature: CGA-362622, N-([4,6-dimethoxy-2-pyrimidinyl]carbamoyl)-3- (2,2,2,-trifluoroethoxy)-pyridin-2-sulfonamide sodium salt; purple nutsedge, Cyperus rotundus L. CYPRO; yellow nutsedge, Cyperus esculentus L. CYPES. Key words: Acropetal translocation, basipetal translocation, half-life. Purple and yellow nutsedge are herbaceous perennial weeds that are among the world’s worst pests (Stoller and Sweet 1987). Holm et al. (1977) listed purple nutsedge as the world’s worst weed and yellow nutsedge as the 16th worst weed. Cyperus species are especially problematic in the southeastern United States, primarily because of their peren- nial nature, longevity of tubers, and prolific tuber produc- tion (Bariuan et al. 1999). Successful control of Cyperus spe- cies with foliar-applied herbicides requires rapid absorption and translocation to the meristematic regions of the basal bulb, rhizomes, and tubers (Sprankle et al. 1975). But in- creased use of herbicides that inadequately control Cyperus species has created a niche for these weeds by eliminating interspecific weed competition (Bendixen and Stroube 1977). Purple and yellow nutsedge are among the 10 most trou- blesome weeds in cotton (Gossypium hirsutum L.) (Dowler 1998). In the past, cotton growers have relied on a preplant- incorporated treatment of norflurazon, followed by either DSMA or MSMA postemergence-directed, followed by sev- eral cultivations for acceptable nutsedge control (McLean et al. 2001; Wilcut et al. 1995; York 1994). But recent her- bicide developments have expanded the postemergence op- tions for selective control of nutsedge in cotton. Currently, pyrithiobac is the only selective, postemergence-applied her- bicide registered for use in nontransgenic cotton that offers some control of purple and yellow nutsedge (Wilcut 1998). CGA-362622 is a new sulfonylurea herbicide being de- veloped for postemergence weed control in nontransgenic and transgenic cotton and sugarcane (Saccharum spp.) (Hol- loway et al. 2000; Hudetz et al. 2000; Porterfield et al. 2002a, 2002b; Wells et al. 2000). CGA-362622, as a sul- fonylurea herbicide, inhibits acetolactate synthase (ALS) (EC 4.1.3.18) in susceptible plants (Hudetz et al. 2000). Cotton tolerance is due to limited absorption and rapid me- tabolism (Askew and Wilcut 2002). CGA-362622 controls a broad spectrum of broadleaf weeds in cotton (Holloway et al. 2000; Hudetz et al. 2000; Porterfield et al. 2002a). In addition, control of purple and yellow nutsedge has been reported in greenhouse and field experiments (Brecke et al. 2000; Holloway et al. 2000; Porterfield et al. 2002a; Troxler et al. 2002). Porterfield et al. (2002a) observed that CGA- 362622 controlled yellow nutsedge better than did pyri- thiobac. Several ALS-inhibiting herbicides control purple and yel- low nutsedge, including chlorimuron (Reddy and Bendixen 1988), imazapic (Richburg et al. 1994), imazaquin (Nan- dihalli and Bendixen 1988), imazethapyr (Richburg et al. 1993), and pyrithiobac (Wilcut 1998). Tolerance to sulfo- nylurea and imidazolinone herbicides is usually due to en- hanced metabolism or substitution of an amino acid in the ALS protein sequence in the tolerant plant species relative to the susceptible species, although differential uptake can contribute to this tolerance (Brown and Neighbors 1987; Eberlein et al. 1999; Wilcut et al. 1989). Reddy and Ben- dixen (1988) attributed the overall susceptibility of purple and yellow nutsedge to chlorimuron to be due to its slow rate of degradation. Basipetal movement of imazaquin to meristems of basal bulbs, roots, and rhizomes of purple and yellow nutsedge has been reported (Nandihalli and Bendixen 1988). Vencill (1998) observed that foliar-applied 14 C-py- rithiobac was mostly translocated to the shoots of yellow nutsedge plants. Because of the potential of CGA-362622 to control purple and yellow nutsedge, its physiological be- havior in these species should be investigated. Therefore, objectives of this research were to evaluate the absorption, translocation, and metabolism of foliar-applied 14 C–CGA- 362622 in purple and yellow nutsedge.