80% control at 35 DAT. Applications Selective Star-of-Bethlehem Control with of imazaquin at 0.50 lb/acre, metsul- and Mixtures of furon at 0.031 lb/acre, and halosul- furon at 0.06 lb/acre did not provide and Topramezone with and effective control (<30%) at 35 DAT when applied alone; however, when in Cool-season Turfgrass applied in combination with bromox- ynil at 1.11 lb/acre, each of those 1,2 1 1 treatments provided >80% control at James T. Brosnan , Gregory R. Armel , William E. Klingeman III , 35 DAT (Main et al., 2004). Gregory K. Breeden1, Jose J. Vargas1, and Philip C. Flanagan1 Carfentrazone-ethyl inhibits pro- toporphyrinogen IX oxidase [protox (E.C. 1.3.3.4)] in the bio- ADDITIONAL INDEX WORDS. HPPD inhibition, Ornithogalum umbellatum, synthesis pathway, increasing the pro- photosystem II, protox, synergy, tank-mixture duction of reactive oxygen species in SUMMARY. Star-of-bethlehem (Ornithogalum umbellatum) commonly invades susceptible plants (Senseman, 2007). turfgrass stands throughout the transition zone. Field experiments were conducted Askew and Willis (2006) reported to evaluate sulfentrazone and mixtures of mesotrione and topramezone with that carfentrazone-ethyl at 0.06 lb/ bromoxynil and bentazon for selective star-of-bethlehem control in cool-season acre provided 96% control of star-of- turf. At 4 weeks after treatment (WAT), applications of sulfentrazone at 0.25 and bethlehem 1 month after treatment; 0.38 lb/acre provided >95% control of star-of-bethlehem in 2008 and 2009. Star- however, this exceeds the maximum of-bethlehem control following applications of commercial prepackaged mixtures labeled use rate of 0.031 lb/acre (FMC containing sulfentrazone was not significantly different from applications of sulfentrazone alone, at either rate, at 4 WAT in 2008 and 2009. Control with Professional Products, 2006a). Se- carfentrazone-ethyl at 0.03 lb/acre measured to <75% at 4 WAT each year. Star- quential applications of carfentrazone- of-bethlehem control at 2, 3, and 4 WAT with topramezone at 0.033 lb/acre was ethyl at 0.031 lb/acre in combination increased by 77%, 50%, and 46%, respectively, from the addition of bromoxynil at with did not increase control 0.50 lb/acre. Similarly, the inclusion of bromoxynil at 0.50 lb/acre increased the compared with carfentrazone alone level of control observed following treatment with mesotrione at 0.28 lb/acre by at 0.053 lb/acre (Askew and Willis, 77%, 30%, and 32% at 2, 3, and 4 WAT. These data suggest that sulfentrazone and 2006). No tall fescue (Festuca arundi- mixtures of topramezone and mesotrione with bromoxynil can be used to provide nacea) injury was observed following postemergence control of star-of-bethlehem in cool-season turf. either treatment. Sulfentrazone is a protox inhibi- tar-of-bethlehem is a perennial aerification practices (Main et al., torinthesamechemicalclassascarfen- weed of managed turfgrass areas 2004). These star-of-bethlehem in- trazone-ethyl that can be absorbed by Sthroughout the upper transition festations negatively affect the aes- the roots and shoots of treated plants zone of the United States. Plants thetic and functional quality of golf (Senseman, 2007). Like carfentrazone, grow from bulbs that are 2 to 3 cm course fairways (Main et al., 2004). sulfentrazone is labeled for use on long, producing channeled leaves that increasing the pro- several warm- and cool-season turf are 3 to 8 mm in diameter. Leaves are duction of reactive oxygen species species (FMC Professional Products, characterized by their pale, whitish- have shown activity against star-of- 2008a); however, its efficacy against green midrib (Goetz et al., 2003; bethlehem. Bromoxynil is a member star-of-bethlehem is not known. McCarty et al., 2001). Bulbs pro- of the nitrile family that Hydroxyphenylpyruvate dioxy- duce lateral bulblets containing alka- inhibits photosystem II by occupying genase [HPPD (EC 1.13.11.27)]- loids poisonous to grazing animals the QB-binding domain on the D1 inhibiting herbicides prevent the carot- (Facciola, 1990). In Tennessee, star- protein, inhibiting electron flow enoid system from quenching reactive of-bethlehem begins to flower in early from photosystem II to photosystem oxidizing energy; thus, May and enters dormancy by early I (Senseman, 2007). This action pre- biosynthesis is disrupted, resulting in June (Main et al., 2004). vents the carotenoid system from chlorophyll destruction, lipid oxida- Star-of-bethlehem can invade quenching reactive oxidizing energy tion, and membrane breakdown (Lee open areas lacking plant competition (Hess, 2000). Main et al. (2004) re- et al., 1997). These herbicides act by (Haragan, 1991; Uva et al., 1997). ported that applications of bromoxynil inhibiting the enzyme p-HPPD re- Infestations have been reported on at 1.11 lb/acre provided 78% control sponsible for converting hydroxyphe- golf course fairways in Tennessee by 21 d after treatment (DAT) and nylpyruvate to homogentisate, from that have been associated with core

We thank the support staff at the East Tennessee Research and Education Center-Plant Sciences Unit Units (Knoxville, TN) for their assistance on this project. To convert U.S. to SI, To convert SI to U.S., 1 Assistant Professor, Assistant Professor, Associate multiply by U.S. unit SI unit multiply by Professor, Extension Assistant, Research Assistant, and Research Associate, Department of Plant Sci- 9.3540 gal/acre LÁha–1 0.1069 ences, University of Tennessee, 252 Ellington Plant 2.54 inch(es) cm 0.3937 Sciences Building, 2431 Joe Johnson Drive, Knoxville, 25.4 inch(es) mm 0.0394 TN 37996 1.1209 lb/acre kgÁha–1 0.8922 2Corresponding author. E-mail: [email protected]. (F – 32) O 1.8 F C(1.8·C) + 32

• April 2010 20(2) 315 RESEARCH REPORTS which a- and plastoqui- sulfentrazone provided greater con- 0.25 lb/acre + bromoxynil at 0.50 lb/ nones are synthesized (Hess, 2000; trol of star-of-bethlehem than the acre; 9) untreated control. All treat- Lee et al., 1997). Two commonly used current commercial standards of car- ments containing mesotrione were HPPD-inhibiting herbicides are meso- fentrazone-ethyl and bromoxynil, applied with a nonionic surfactant at trione and topramezone. Mesotrione, and to evaluate the efficacy of me- a 0.25% (v/v) ratio. Treatments de- a triketone herbicide, is registered for sotrione and topramezone applied livering topramezone, bentazon, or preemergence (PRE) and postemer- alone and in mixtures with photosys- bromoxynil (alone or in combination gence (POST) control of broadleaf tem II-inhibiting herbicides for con- with one another) included a crop oil and grassy weeds in turf ( trol of star-of-bethlehem. concentrate at a 1% (v/v) ratio. Treat- Professional Products, 2008b). Top- ments were applied POST on 10 Mar. ramezone is a pyrazolone herbicide Materials and methods 2009 and were replicated at an adja- registered for control of broadleaf and Field studies designed to meet cent location later that spring. grassyweedsincorn[Zea mays the first objective were referred to as TREATMENT APPLICATION AND (AMVAC, 2006b)]. Mesotrione and ‘‘single product experiments’’ while DATA COLLECTION. All treatments were topramezone cause foliar bleaching of those designed to meet objective two applied with a carbon dioxide-powered susceptible species (Mitchell et al., were referred to as ‘‘mixture experi- backpack boom sprayer calibrated to 2001); however, the efficacy of these ments.’’ These experiments were con- deliver 30 gal/acre of spray volume. herbicides against star-of-bethlehem ducted in Spring 2008 and Spring The sprayer boom contained four flat- has not been reported. 2009 on a mature stand of tall fescue fan nozzles (Tee Jet XR8002 flat-fan Mixtures of HPPD and photo- turf infested with star-of-bethlehem nozzles; Spraying Systems, Roswell, system II-inhibiting herbicides, like (60%) at the East Tennessee Re- GA) spaced 10 inches apart. A wheeled and bromoxynil, have been search and Education Center-Plant aluminum frame maintained the boom reported to provide increased weed Sciences Unit, Knoxville, TN. Plots height at 10 inches above the surface control in various cropping systems. were established on a Sequatchie loam while spraying. Armel et al. (2003, 2005) found that soil [Fine-loamy, siliceous, semiactive, Star-of-bethlehem control was mixtures of mesotrione at 0.09 lb/ thermic humic Hapludult], measuring rated visually from 0% (no injury) to acre and atrazine at 0.250 lb/acre 6.2 in soil pH and 2.1% in organic 100% (plant death) at 1, 2, 3, and 4 provided an improved level of horse- matter content. Field trials were con- WAT. Tall fescue injury was rated nettle (Solanum carolinense) and can- ducted in an area of full sunlight and using the same 0% to 100% scale on ada thistle (Cirsium arvense) control maintained as a utility turf with respect the same evaluation dates. Weed con- over mesotrione alone at 0.09 lb/ to irrigation, fertility, and mowing trol and turf injury were assessed acre. Johnson et al. (2002) reported during both years. Plots were mowed visually, as Yelverton et al. (2009) improved ivy-leaf morningglory (Ipo- at 4 inches height-of-cut with a rotary reported that visual ratings of herbi- moea hederacea) and yellow nutsedge mower twice monthly. cide responses in turf were highly (Cyperus esculentus) control with mix- SINGLE PRODUCT EXPERIMENT. correlated with data collected using tures of mesotrione at 0.062 lb/acre Treatments for the single product the line intersect method or digital and atrazine at 0.226 lb/acre. Aben- experiment were: 1) bromoxynil at image analysis. droth et al. (2006) reported a syner- 0.50 lb/acre; 2) mesotrione at 0.25 STATISTICAL ANALYSIS. All exper- gistic effect in sunflower (Helianthus lb/acre plus a nonionic surfactant at iments were arranged in a randomized annuus) control when mixing meso- a 0.25% (v/v) ratio; 3) sulfentrazone complete block design with three trione at 0.008, 0.016, and 0.031 lb/ at 0.25 lb/acre; 4) sulfentrazone at replications. In each instance, the un- acre with atrazine at 0.250 lb/acre 0.38 lb/acre; 5) carfentrazone-ethyl treated control was deleted to stabi- and bromoxynil at 0.06 lb/acre. Syn- at 0.03 lb/acre; 6) sulfentrazone at lize variance (Willis et al., 2007). Data ergistic responses in the control of 0.06 lb/acre + at 0.50 lb/ were subjected to analysis of variance velvetleaf (Abutilon theophrasti) and acre + 2,4-D at 0.88 lb/acre + using PROC GLM in SAS (version palmer amaranth (Amaranthus pal- dicamba at 0.10 lb/acre; 7) sulfen- 9.1; SAS Institute, Cary, NC) with meri) have been reported for mixtures trazone at 0.03 lb/acre + 2,4-D at the factor ‘‘replication’’ analyzed as of mesotrione with atrazine or bro- 0.70 lb/acre + MCPP at 0.25 lb/acre + a random variable. Fisher’s protected moxynil (Abendroth et al., 2006) as dicamba at 0.11 lb/acre; 8) untreated least significant difference values are well. In turfgrass, Willis et al. (2007) control. Treatments were applied reported for treatment comparisons reported that mixtures of mesotrione POSTon7Apr.2008and10Mar. at the a = 0.05 level (Clewer and with bromoxynil and atrazine pro- 2009. Scarisbrick, 2001). vided an improved level of white MIXTURE EXPERIMENT. Treat- clover (Trifolium repens) control ments for the mixture experiment Results and discussion compared with these materials ap- were: 1) topramezone at 0.033 lb/ SINGLE PRODUCT EXPERIMENT. plied alone. The efficacy of mixtures acre; 2) mesotrione at 0.25 lb/acre; 3) The year by treatment interaction for containing topramezone, another bentazon at 0.50 lb/acre; 4) bromox- the single product experiment was HPPD-inhibiting herbicide, with ynil at 0.50 lb/acre; 5) topramezone statistically significant; thus, data from photosystem II-inhibiting herbicides at 0.033 lb/acre + bentazon at 0.50 each year are presented individually. like atrazine and bromoxynil has not lb/acre; 6) topramezone at 0.033 lb/ By 4 WAT, applications of sul- been reported. acre + bromoxynil at 0.50 lb/acre; 7) fentrazone at 0.25 and 0.38 lb/acre The objectives of this research mesotrione at 0.25 lb/acre + benta- provided >95% control in 2008 and were to determine if mesotrione and zon at 0.50 lb/acre; 8) mesotrione at 2009. While carfentrazone-ethyl at

316 • April 2010 20(2) 0.03 lb/acre provided >93% control rating date (Table 1). These results high as 78% control at 3 WAT (Table by 2 WAT in both years, control at 4 differ from those reported by Main 2). Similarly, bromoxynil applications WAT had reduced to 58% and 73% in et al. (2004), who found applications at 0.50 lb/acre only provided as high 2008 and 2009, respectively (Table 1). of bromoxynil at 1.11 lb/acre to as 72% control of star-of-bethlehem These results differ from those re- provide greater than 80% control of at 4 WAT in the single product ex- ported by Askew and Willis (2006) star-of-bethlehem at 35 DAT. How- periment (Table 1). who reported that a single applica- ever, the researcher’s application rate The level of control reported fol- tion of carfentrazone-ethyl at 0.06 lb/ in that study was much greater than lowing treatments of topramezone and acre provided 96% control of star-of- that which was used in this study mesotrione mixed with bromoxynil at bethlehem at 4 WAT. (0.50 lb/acre). 0.50 lb/acre was significantly greater In both years, star-of-bethlehem MIXTURE EXPERIMENT. No sig- than that which was observed when control following applications of com- nificant interactions were detected either herbicide was applied alone. By mercial premixtures containing sulfen- between runs of the mixture experi- adding bromoxynil at 0.50 lb/acre, trazone was not significantly different ment; therefore, these data were com- star-of-bethlehem control at 2, 3, and from sulfentrazone alone at either rate bined (Table 2). 4 WAT with topramezone was in- at 4 WAT (Table 1). Askew and Willis Star-of-bethlehem control follow- creased 77%, 50%, and 46%, respec- (2006) reported similar results for ing applications of topramezone at tively (Table 2). A similar response was carfentrazone-ethyl applied alone and 0.033 lb/acre and mesotrione at 0.25 reported for mesotrione on each rating in combination with dicamba. Since lb/acre measured <5% at 2 WAT (Table date. Mixtures of topramezone at Main et al. (2004) reported that com- 2). By 4 WAT, an application of top- 0.033 lb/acre or mesotrione at 0.25 mercial premixtures of synthetic ramezone at 0.033 lb/acre provided lb/acre with bromoxynil at 0.50 lb/ herbicides only provided 15% control 47% control of star-of-bethlehem, while acre provided 93% control of star-of- of star-of-bethlehem at 35 DAT in mesotrione at 0.25 lb/acre provided bethlehem at 4 WAT (Table 2). Tennessee, these results suggest that 61% control on the same evaluation Mixtures of mesotrione plus ben- the addition of a protox-inhibiting date. These data are similar to those tazon at 0.50 lb/acre improved star- herbicide to a premixture of synthetic reported in the single product experi- of-bethlehem control compared with auxin herbicides can improve efficacy ment where mesotrione applications at mesotrione alone. Star-of-bethlehem against star-of-bethlehem. 0.25 lb/acre only provided 50% and control at 2 and 4 WAT with meso- Bromoxynil and mesotrione 43% control of star-of-bethlehem at 4 trione was increased 22% by adding provided a significantly lower level of WAT in 2008 and 2009, respectively bentazon at 0.50 lb/acre (Table 2). control than either of the protox- (Table 1). Bentazon applied alone provided inhibiting herbicides evaluated in Neither of the photosystem II- <33% control of star-of-bethlehem 2009. Bromoxynil at 0.50 lb/acre inhibiting herbicides provided >78% throughout the study. Control follow- provided only 17% control of star- control of star-of-bethlehem. The ing applications of topramezone at of-bethlehem by 4 WAT in 2009, highest level of control reported fol- 0.033 lb/acre mixed with bentazon while control following an application lowing treatment with bentazon at at 0.50 lb/acre was not significantly of mesotrione at 0.25 lb/acre only 0.50 lb/acre was 32% at 4 WAT, different from topramezone alone at provided 43% control at the same while bromoxynil only provided as 0.033 lb/acre on any rating date;

Table 1. Percentage of visual control of star-of-bethlehem in the single product experiment conducted at the East Tennessee Research and Education Center-Plant Sciences Unit (Knoxville, TN) in 2008 and 2009. Star-of-bethlehem control (%) 2008 2009 Herbicide Rate 1 WATz 2 WAT 3 WAT 4 WAT 1 WAT 2 WAT 3 WAT 4 WAT Treatment (lb/acre)y (%) Bromoxynil 0.50 48 93 43 72 0 20 33 17 Carfentrazone-ethyl 0.03 82 97 27 58 60 93 90 73 Mesotrione 0.25 7 52 48 50 0 33 47 43 Sulfentrazone 0.25 83 97 93 100 40 87 100 97 Sulfentrazone 0.38 83 100 95 95 53 92 100 100 Sulfentrazone+ 0.06+ 40 82 68 67 33 90 98 93 Quinclorac + 0.50+ 2,4-D+ 0.88+ Dicamba 0.10 Sulfentrazone+ 0.03+ 23 77 53 70 33 85 99 87 2,4-D+ 0.70+ MCPP+ 0.25+ Dicamba 0.11 x LSD0.05 9 21403222116 11 zWAT = weeks after treatment. y1 lb/acre = 1.1209 kgÁha–1. xFisher’s protected least significant difference value used to compare treatment means at the a = 0.05 level.

• April 2010 20(2) 317 RESEARCH REPORTS

Table 2. Percentage of visual control of star-of-bethlehem for treatments applied Goetz,R.J.,T.N.Jordan,J.W.McCain,and in the mixture experiment conducted at the East Tennessee Research and N.Y. Su. 2003. Indiana plants poisonous to Education Center-Plant Sciences Unit (Knoxville, TN) in 2009. livestock and pets: Star-of-bethlehem. 18 May 2009. . Herbicide Rate 1 WATz 2 WAT 3 WAT 4 WAT treatment (lb/acre)y (%) Haragan, P.D. 1991. Weeds of Kentucky and adjacent states: A field guide. Univer- Bentazonx 0.50 2 9 32 32 sity Press of Kentucky, Lexington, KY. Bromoxynilx 0.50 12 78 78 74 Mesotrionew 0.25 0 5 63 61 Hess, F.D. 2000. Review: Light-dependent herbicides: An overview. Weed Sci. Mesotrionew + bentazonw 0.25 + 0.50 3 28 73 82 48:160–170. Mesotrionew + bromoxynilw 0.25 + 0.50 15 82 93 93 Topramezonex 0.033 2 5 43 47 Johnson, B.C., B.G. Young, and J.L. Topramezonex + bentazonx 0.033 + 0.50 2 12 58 63 Matthews. 2002. Effect of postemergence Topramezonex + bromoxynilx 0.033 + 0.50 18 82 93 93 application rate and timing of mesotrione on corn (Zea mays) response and weed LSD v 6141719 0.05 control. Weed Technol. 16:414–420. zWAT = weeks after treatment. y1 lb/acre = 1.1209 kgÁha–1. Lee,D.L.,M.P.Prisbylla,T.H.Cromartie, x Mixed with crop oil concentrate at a 1% (v/v) ratio. D.R. Dagarin, S.W. Howard, W.M. Provan, wMixed with a nonionic surfactant at a 0.25% (v/v) ratio. vFisher’s protected least significant difference value used to compare treatment means (pooled across two M.K. Ellis, T. Fraser, and L.C. Mutter. 1997. experimental runs of a study with three replications) at the a = 0.05 level. The discovery and structural requirements of inhibitors of p-hydroxyphenylpyruvate dioxygenase. Weed Sci. 45:601–609. however, by 3 and 4 WAT, this mix- tions of mesotrione and photosystem II ture provided greater control than an inhibitors. Weed Technol. 20:267–274. Main, C.L., D.K. Robinson, T.C. Teuton, application of bentazon alone at 0.50 and T.C. Mueller. 2004. Star-of-bethle- AMVAC. 2006b. Impact herbicide label. hem (Ornithogalum umbellatum) control lb/acre (Table 2). AMVAC, Los Angeles. Although mesotrione has been with postemergence herbicides in dor- Armel, G.R., G.J. Hall, H.P. Wilson, and mant bermudagrass (Cynodon dactylon) reported to temporarily injure tall fes- turf. Weed Technol. 18:1117–1119. cue turf (Syngenta Professional Prod- N. Cullen. 2005. Mesotrione plus atra- zine mixtures for control of canada thistle ucts, 2008b), at no time in the single McCarty, L.B., J.W. Everest, D.W. Hall, (Cirsium arvense). Weed Sci. 53:202– T.R. Murphy, and F.H. Yelverton. 2001. product or mixture experiment was tall 211. fescue injury observed with any treat- Color atlas of turfgrass weeds. Ann Arbor ment (data not shown). This may be Armel,G.R.,H.P.Wilson,R.J.Richardson, Press, Chelsea, MI. because applications were made in and T.E. Hines. 2003. Mestrione combi- Mitchell, G., D.W. Bartlett, T.E. Fraser, spring under conditions of moderate nations for postemergence control of T.R. Hawkins, D.C. Holt, J.K. Townson, horsenettle (Solanum carolinense)incorn and R.A. Wichert. 2001. Mesotrione: A temperature (<80 F) and low humid- (Zea mays). Weed Technol. 17:65–72. ity (<50%). Other researchers (Brosnan new selective herbicide for use in . and Breeden, 2009; M.J. Goddard, Askew, S.D. and J.B. Willis. 2006. Car- Pest Manag. Sci. 57:120–128. personal communication) have ob- fentrazone for selective star-of-bethlehem Senseman, S.A. 2007. Herbicide hand- served tall fescue injury with meso- control. Proc. Northeastern Weed Sci. book. Weed Science Society of America, trione applications in hot, humid Soc. 60:95(Abstr.). Lawrence, KS. summer weather. Brosnan, J.T. and G.K. Breeden. 2009. Syngenta Professional Products. 2008b. Data collected in these experi- Weed control programs during the spring Tenacity turf herbicide product label. Syn- ments illustrates that turfgrass man- and summer establishment of tall fescue genta Professional Products, Greensboro, agers can apply sulfentrazone to and Kentucky bluegrass in the transition NC. provide POST control of star-of- zone. 2009. Univ. Tennessee Turfgrass bethlehem in cool-season turf. Similar Weed Sci. Annu. Res. Rpt. p. 84–98. Uva, R.H., J.C. Neal, and J.M. DiTomaso. 1997. Weeds of the northeast. Cornell to what has been reported for other Clewer, A.G. and D.H. Scarisbrick. 2001. University Press, Ithaca, NY. weed species, the inclusion of bromox- Practical statistics and experimental de- ynil with topramezone and meso- sign for plant and crop science. Wiley, Willis, J.B., S.D. Askew, and J.S. McElroy. trione significantly increases the level Hoboken, NJ. 2007. Improved white clover control with mesotrione by mixing bromoxynil, car- of star-of-bethlehem control provided Facciola, S. 1990. Star-of-bethlehem, p. by these herbicides. These tank mix- fentrazone, and . Weed Technol. 126. In: S. Facciola (ed.). Cornucopia: A 21:739–743. tures may provide additional options source book of edible plants. Kampong, for turfgrass managers charged with Vista, CA. Yelverton, F.H., J.A. Hoyle, T.W. Gannon, and L.S. Warren. 2009. Plant counts, controlling star-of-bethlehem infesta- FMC Professsional Products. 2006a. tions in cool-season turf. digital image analysis, and visual ratings Quicksilver T&O herbicide product label. for estimating weed control in turf: Are FMC Professsional Products, Philadelphia. they correlated? Proc. Southern Weed Sci. Literature cited FMC Professional Products. 2008a. Dis- Soc. (Abstr.) (In press). Abendroth, J.A., A.R. Martin, and F.W. miss turf herbicide product label. FMC Roeth. 2006. Plant response to combina- Professsional Products, Philadelphia.

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