80% control at 35 DAT. Applications Selective Star-of-Bethlehem Control with of imazaquin at 0.50 lb/acre, metsul- Sulfentrazone and Mixtures of Mesotrione furon at 0.031 lb/acre, and halosul- furon at 0.06 lb/acre did not provide and Topramezone with Bromoxynil and effective control (<30%) at 35 DAT when applied alone; however, when Bentazon 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 chlorophyll 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 dicamba 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 Herbicides 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 herbicide 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, carotenoid 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-tocopherols 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 (Syngenta 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 atrazine 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.