Matthew T. Elmore

Nitrogen-Enhanced Efficacy of Mesotrione and Topramezone for Smooth Crabgrass (Digitaria ischaemum) Control

Abstract The herbicides mesotrione and topramezone inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD) and have efficacy against smooth crabgrass. Research was conducted to determine the impacts of soil-applied nitrogen (N) fertilizer on the effectiveness of single applications of mesotrione and topramezone for postemergence smooth crabgrass control. Field experiments in 2010 and 2011 evaluated the efficacy of mesotrione (280 g a.i. ha−1) and topramezone (9 g a.i. ha−1) for control of multitiller smooth crabgrass subjected to five N fertility treatments (0, 12, 25, 37, or 49 kg N ha−1). Greenhouse experiments evaluated the response of smooth crabgrass to mesotrione (0, 70, 140, 280, 560, and 1,120 g ha−1) and topramezone (0, 4.5, 9, 18, 36, and 72 g ha−1) with 0 or 49 kg N ha−1. Further research evaluated changes in smooth crabgrass leaf tissue pigment concentrations following treatment with mesotrione (280 g ha−1) and topramezone (18 g ha−1) with 0 or 49 kg N ha−1. In field experiments, N increased smooth crabgrass control with mesotrione and topramezone for 8 wk; however, increasing N rate above 25 kg ha−1 did not improve control on any rating date. In dose-response experiments, N application reduced I50 values for mesotrione and topramezone by 67 and 53%, respectively, 21 d after treatment (DAT). Reductions in aboveground biomass with both herbicides were greater when applied following N treatment as well. In leaf-response experiments, N decreased new leaf chlorophyll and carotenoid concentrations and new leaf production after treatment with topramezone. Future research should investigate whether increased translocation of these herbicides to meristimatic regions contribute to N-enhanced efficacy. Nomenclature: Mesotrione, smooth crabgrass (Digitaria ischaemum Schreb. ex Muhl.); topramezone.

Influence of Herbicide Safeners on Creeping Bentgrass (Agrostis stolonifera) Tolerance to Herbicides

Abstract Glasshouse research was conducted to investigate the efficacy of herbicide safeners for improving creeping bentgrass (CBG) tolerance to various herbicides. CBG injury from amicarbazone (150 g ha−1), bispyribac-sodium (110 g ha−1), fenoxaprop-p-ethyl (35 g ha−1), imazapic (45 g ha−1), quinclorac (1,050 g ha−1), or topramezone (37 g ha−1) applied in combination with the herbicide safeners naphthalic anhydride or isoxadifen-ethyl was evaluated. These safeners reduced CBG injury from topramezone only. Topramezone was then applied in combination with naphthalic anhydride, isoxadifen-ethyl, cloquintocet-mexyl (cloquintocet), fenchlorazole-ethyl, mefenpyr-diethyl, and benoxacor. These experiments determined that CBG injury was lowest from topramezone in combination with cloquintocet. Additional experiments evaluated topramezone (37 g ha−1) with several rates of cloquintocet and determined that applications at ≥ 28 g ha−1 reduced CBG injury similarly. Cloquintocet (28 g ha−1) increased topramezone I50 values against CBG, but not large crabgrass or goosegrass. The cytochrome P450 (cP450) inhibitor malathion (1000 g ha−1) reduced topramezone I50 values against CBG in one experimental run. Topramezone–cloquintocet combinations warrant further research in field settings. Nomenclature: Amicarbazone; benoxacor; bispyribac-sodium; cloquintocet-mexyl; fenchlorazole-ethyl; fenoxaprop-p-ethyl; imazapic; isoxadifen-ethyl; malathion; mefenpy-diethyl; naphthalic anhydride; quinclorac; topramezone; creeping bentgrass, Agrostis stolonifera L.; goosegrass, Eleusine indica (L.) Gaertn.; large crabgrass, Digitaria sanguinalis (L.) Scop. Resumen En un estudio en invernadero, se investigó la eficacia de antídotos de herbicidas para mejorar la tolerancia del césped Agrostis stolonifera (CBG) a varios herbicidas. Se evaluó el daño en CBG causado por amicarbazone (150 g ai ha−1), bispyribac-sodium (110 g ai ha−1), fenoxaprop-p-ethyl (35 g ai ha−1), imazapic (45 g ai ha−1), quinclorac (1,050 g ai ha−1), o topramezone (37 g ai ha−1) aplicados en combinación con los antídotos de herbicidas naphthalic anhydride o isoxadifen-ethyl. Estos antídotos solamente redujeron el daño causado por topramezone. Posteriormente, se aplicó topramezone en combinación con naphthalic anhydride, isoxadifen-ethyl, cloquintocet-mexyl (cloquintocet), fenchlorazole-ethyl, mefenpy-diethyl, y benoxacor. Estos experimentos determinaron que el menor daño en CBG se dio con topramezone combinado con cloquintocet. Experimentos adicionales evaluaron topramezone (37 g ha−1) con varias dosis de cloquintocet y se determinó que las aplicaciones a ≥ 28 g ha−1 redujeron el daño en CBG en forma similar. Cloquintocet (28 g ai ha−1) incrementó los valores de I50 de topramezone en CBG, pero no en Digitaria sanguinalis o Eleusine indica. El inhibidor del cytochrome P450 (cP450) malathion (1000 g ai ha−1) redujo los valores de I50 de topramezone en una de las corridas experimentales. El uso de combinaciones de topramezone con cloquintocet debe ser investigado en condiciones de campo.

Mesotrione, Topramezone, and Amicarbazone Combinations for Postemergence Annual Bluegrass (Poa annua) Control

Abstract Selective annual bluegrass (ABG) control with mesotrione is often inconsistent, and sequential applications might be required for complete control. The complementary nature of p-hydroxyphenylpyruvate dioxygenase (HPPD)- and photosystem II (PSII)-inhibiting herbicides is well documented. The HPPD-inhibiting herbicide mesotrione and the PSII-inhibiting herbicide amicarbazone both have efficacy against annual bluegrass and safety on certain cool-season turfgrasses. Topramezone is a HPPD-inhibiting herbicide being investigated for use in turfgrass. Field and greenhouse experiments were conducted to examine single applications of topramezone and mesotrione alone or in combination with amicarbazone for POST ABG control in spring. In greenhouse experiments, the combination of mesotrione (280 g ai ha−1) and amicarbazone (75 g ai ha−1) controlled ABG 70% by 21 d after treatment, > 29% more than either herbicide applied alone; these combinations were determined to be synergistic. Amicarbazone combined with topramezone (14.5 g ai ha−1) provided < 10% ABG control and was not synergistic. When combined with mesotrione, increasing amicarbazone rate to 150 or 255 g ha−1 did not increase ABG control compared to 75 g ha−1in field experiments. Combining mesotrione with amicarbazone resulted in a synergistic increase in POST ABG control at 1 and 2 wk after treatment (WAT). When applied alone or in combination with amicarbazone, increasing the mesotrione rate from 90 to 280 g ha−1 increased efficacy on ABG in field experiments. The combination of mesotrione at 280 g ha−1 and amicarbazone at 75 g ha−1 provided > 90% ABG control in field experiments. Future research should focus on sequential applications of mesotrione–amicarbazone combinations for ABG control in locations where ABG is historically more difficult to control. Nomenclature: Amicarbazone; mesotrione; topramezone; annual bluegrass; Poa annua L. Resumen El control selectivo de Poa annua (ABG) con mesotrione es frecuentemente inconsistente, y aplicaciones secuenciales podrían ser requeridas para alcanzar un control completo. La naturaleza complementaria de los herbicidas inhibidores de p-hydroxyphenylpyruvate dioxygenase (HPPD)- y del fotosistema II (PSII) está bien documentada. El herbicida mesotrione, inhibidor de HPPD, y amicarbazone, inhibidor de PSII, son efectivos contra ABG y son seguros en varios céspedes de clima frío. Topramezone es un herbicida inhibidor de HPPD que está siendo investigado para su uso en céspedes. Se realizaron experimentos de campo y de invernadero para examinar aplicaciones simples de topramezone y de mesotrione solos y en combinación con amicarbazone para el control POST de ABG en la primavera. En los experimentos de invernadero, la combinación de mesotrione (280 g ai ha−1) y amicarbazone (75 g ai ha−1) controlaron ABG 70% a 21 días después del tratamiento, >29% más que cualquiera de estos herbicidas aplicados solos; estas combinaciones fueron consideradas sinérgicas. La combinación de amicarbazone con topramezone (14.5 g ai ha−1) brindó <10% de control de ABG y no fue sinérgica. Cuando se combinó con mesotrione, el incrementar la dosis de amicarbazone a 150 ó 255 g ha−1 no incrementó el control de ABG al compararse con 75 g ha−1 en los experimentos de campo. El combinar mesotrione con amicarbazone resultó en un aumento sinérgico en el control POST de ABG a 1 y 2 semanas después del tratamiento (WAT). Cuando se aplicó amicarbazone solo o en combinación, el aumentar la dosis de mesotrione de 90 a 280 g ha−1 incrementó la eficacia sobre ABG en los experimentos de campo. La combinación de mesotrione a 280 g ha−1 con amicarbazone a 75 g ha−1 brindó >90% de control de ABG en los experimentos de campo. Investigaciones futuras deberían enfocarse en aplicaciones secuenciales de combinaciones de mesotrione-amicarbazone para el control en sitios donde históricamente ABG ha sido más difícil de controlar.

Seasonal Application Timings Affect Dallisgrass (Paspalum dilatatum) Control in Tall Fescue

Abstract Field research was conducted in 2010 and 2011 to investigate the efficacy of herbicides for dallisgrass control when applied at various growing (GDD) or cooling degree day (CDD) –based application timings. Herbicide treatments included fluazifop-p-butyl (fluazifop; 105 g ai ha−1), mesotrione (280 g ai ha−1), tembotrione (92 g ai ha−1), topramezone (37 g ai ha−1), and tank mixtures of fluazifop plus mesotrione, tembotrione, or topramezone. Herbicide treatments were applied at either 75, 175, 375, 775 GDD, or 5 CDD. Treated plots were subjected to three tall fescue interseeding regimes: no seeding, seeding in spring, or seeding in fall (0, 353, and 353 kg pure live seed ha−1, respectively). In 2010, dallisgrass control from fluazifop applied at 75, 375, and 775 GDD was poor (< 50%) by 52 wk after treatment (WAT); in 2011, control from fluazifop application at these timings was higher (62 to 72%). When applied at 175 GDD or 5 CDD in 2010 and 2011, dallisgrass control from fluazifop ranged from 79 to 93% at 52 WAT. The addition of mesotrione, tembotrione, or topramezone to fluazifop did not affect dallisgrass control at any application timing, and control provided by these herbicides alone was low (< 65%). Interseeding tall fescue in the fall improved dallisgrass control from herbicides applied at 75 GDD in 2010 and 175, 375, and 775 GDD at 52 WAT in both years. Results suggest that timing of fluazifop applications at 175 GDD and 5 CDD enhances dallisgrass control. Nomenclature: Fluazifop-p-butyl; mesotrione; tembotrione; topramezone; dallisgrass; Paspalum dilatatum Poir.; tall fescue; Lolium arundinaceum (Schreb.) S.J. Darbyshire. Resumen En 2010 y 2011, se realizó un estudio de campo para investigar la eficacia de herbicidas para el control de Paspalum dilatatum, cuando estos se aplicaron en diferentes momentos basándose en grados día de crecimiento (GDD) o enfriamiento (CDD). Los tratamientos de herbicidas incluyeron fluazifop-p-butyl (fluazifop; 105 g ai ha−1), mesotrione (280 g ai ha−1), tembotrione (92 g ai ha−1), topramezone (37 g ai ha−1), y mezclas en tanque de fluazifop más mesotrione, tembotrione, o topramezone. Los tratamientos de herbicidas fueron aplicados ya fuera a 75, 175, 375, 775 GDD, o 5 CDD. Las parcelas tratadas fueron sometidas a regímenes de entre-siembra con Lolium arundinaceum: sin siembra, siembra en la primavera, o siembra en el otoño (0, 353, y 353 kg de semilla pura viva ha−1, respectivamente). En 2010, el control de P. dilatatum con fluazifop aplicado a 75, 375 y 775 GDD fue pobre (<50%) a 52 semanas después del tratamiento (WAT). En 2011, el control con la aplicación de fluazifop en estos mismos momentos fue mayor (62 a 72%). Cuando se aplicó a 175 GDD o 5 CDD en 2010 y 2011, el control con fluazifop de P. dilatatum varió entre 79 y 93% a 52 WAT. La adición de mesotrione, tembotrione, o topramezone al fluazifop no afectó el control de P. dilatatum en ninguno de los momentos de aplicación, y el control brindado por estos herbicidas aplicados solos fue bajo (<65%). La entre-siembra de L. arundinaceum en el otoño mejoró el control de P. dilatatum para herbicidas aplicados a 75 GDD en 2010 y 175, 375, y 775 GDD a 52 WAT, en ambos años. Los resultados sugieren que realizar aplicaciones de fluazifop a 175 GDD y 5 CDD mejora el control de P dilatatum.

Application Timing Affects Bermudagrass Suppression with Mixtures of Fluazifop and Triclopyr

Abstract Bermudagrass is a troublesome weed of zoysiagrass golf-course fairways. Field research was conducted in 2009 and 2010 evaluating bermudagrass suppression with applications of fluazifop plus triclopyr at various timings. Three rates of fluazifop (0.10, 0.21, and 0.32 kg ai ha−1) were applied with triclopyr (1.12 kg ae ha−1) once six thresholds of growing-degree-day accumulation (GDD10C) had been reached: 200, 450, 825, 1,275, 1,775, and 2,250 GDD10C. Yearly accumulated GDD10C values were calculated with a base temperature of 10 C beginning on 1 January. Applications at 200 and 2,250 GDD10C suppressed bermudagrass ≥ 90% at 5 WAT each year. Increased rates of fluazifop did not provide additional bermudagrass suppression at these timings. Cooling accumulation models may be needed to time fall applications, as the 1,775 GDD10C timing in 2009 provided similar bermudagrass suppression to the 2,250 GDD10C timing in 2010. Late-spring and midsummer applications at 450 GDD10C, 825 GDD10C, and 1,275 GDD10C only suppressed bermudagrass 4 to 16% at 6 wk after treatment (WAT) in 2009 and 0 to 57% at 6 WAT in 2010. Zoysiagrass injury measured < 25% for all timings and decreased to 0 to 7% by 5 WAT each year. Future studies should evaluate bermudagrass suppression with other herbicides with the use of growing-degree-day and cooling accumulation models. Nomenclature: Fluazifop; triclopyr; bermudagrass (Cynodon dactylon L. Pers.) ‘Riviera’; zoysiagrass (Zoysia japonica Steud.) ‘Zenith’.

Response of Hybrid Bermudagrass (Cynodon dactylon × C. transvaalensis) to Three HPPD-Inhibitors

Abstract Mesotrione, topramezone, and tembotrione inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD), an enzyme integral to carotenoid biosynthesis. Research was conducted to evaluate the response of hybrid bermudagrass following mesotrione (280, 350, and 420 g ai ha−1), topramezone (18, 25, and 38 g ai ha−1), and tembotrione (92, 184, and 276 g ai ha−1) applications. Measurements of visual bleaching (VB) and chlorophyll fluorescence yield (Fv/Fm) were evaluated 3, 5, 7, 14, 21, 28, and 35 d after application (DAA). Leaf tissues were sampled on the same dates and assayed for chlorophyll and carotenoid pigments using high-performance liquid chromatography (HPLC). Responses of plants treated with topramezone and tembotrione were similar; these herbicides caused more VB and greater reductions in Fv/Fm, total chlorophyll, lutein, and xanthophyll cycle pigment concentrations than mesotrione 5 to 21 DAA. Increasing mesotrione application rate did not increase VB or lead to greater reductions in total chlorophyll, lutein, or xanthophyll pigment concentrations. Alternatively, increasing topramezone and tembotrione application rates above 18 and 92 g ha−1, respectively, extended VB and pigment reductions. Of the three HPPD-inhibitors tested, topramezone was the most active, because the low (18 g ha−1) rate of topramezone reduced lutein and total xanthophyll pigment concentrations more than the low rate of tembotrione (92 g ha−1) during periods of maximum activity (14 to 21 DAA). No necrosis was observed with any of the treatments, suggesting tank mixtures of topramezone with other herbicides might be required to provide long-term control of hybrid bermudagrass. Nomenclature: Mesotrione; topramezone; tembotrione; hybrid bermudagrass, Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy ‘Tifway’.

Cytochrome P450 Inhibitors Reduce Creeping Bentgrass (Agrostis stolonifera) Tolerance to Topramezone

Creeping bentgrass (Agrostis stolonifera L.) is moderately tolerant to the p-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide topramezone. However, the contribution of plant metabolism of topramezone to this tolerance is unknown. Experiments were conducted to determine if known cytochrome P450 monooxygenase inhibitors 1-aminobenzotriazole (ABT) and malathion alone or in combination with the herbicide safener cloquintocet-mexyl influence creeping bentgrass tolerance to topramezone. Creeping bentgrass in hydroponic culture was treated with ABT (70 μM), malathion (70 μm and 1000 g ha-1), or cloquintocet-mexyl (70 μM and 1000 g ha-1) prior to topramezone (8 g ha-1) application. Topramezone-induced injury to creeping bentgrass increased from 22% when applied alone to 79 and 41% when applied with malathion or ABT, respectively. Cloquintocet-mexyl (70 μM and 1000 g ha-1) reduced topramezone injury to 1% and increased creeping bentgrass biomass and PSII quantum yield. Cloquintocet-mexyl mitigated the synergistic effects of ABT more than those of malathion. The effects of malathion on topramezone injury were supported by creeping bentgrass biomass responses. Responses to ABT and malathion suggest that creeping bentgrass tolerance to topramezone is influenced by cytochrome P450-catalyzed metabolism. Future research should elucidate primary topramezone metabolites and determine the contribution of cytochrome P450 monooxygenases and glutathione S-transferases to metabolite formation in safened and non-safened creeping bentgrass.

Herbicide Safeners Increase Creeping Bentgrass (Agrostis stolonifera) Tolerance to Pinoxaden and Affect Weed Control

The herbicide pinoxaden is a phenylpyrazoline inhibitor of acetyl coenzyme A carboxylase. Research was conducted to determine the effects of pinoxaden (90 g ai ha−1) alone and in combination with herbicide safeners on creeping bentgrass injury as well as perennial ryegrass and roughstalk bluegrass control. Greenhouse experiments determined that herbicide safeners cloquintocet-mexyl, fenchlorazole-ethyl, and mefenpyr-diethyl were more effective in reducing creeping bentgrass injury from pinoxaden than benoxacor, isoxadifen-ethyl, and naphthalic-anhydride. Other experiments determined that creeping bentgrass injury from pinoxaden decreased as rates (0, 23, 45, 68, 90, 225, or 450 g ha−1) of cloquintocet-mexyl, fenchlorazole-ethyl, and mefenpyr-diethyl increased. On the basis of creeping bentgrass responses to various safener rates, safeners were applied at 68 and 450 g ha−1 in additional experiments to evaluate their effects on pinoxaden (90 g ha−1) injury to creeping bentgrass and efficacy against perennial ryegrass and roughstalk bluegrass. In these experiments, safeners mefenpyr-diethyl and cloquintocet-mexyl reduced pinoxaden-induced creeping bentgrass injury (from 25 to ≤ 5%) more than fenchlorazole-ethyl at 2 wk after treatment. Safeners reduced pinoxaden efficacy against roughstalk bluegrass. Perennial ryegrass was controlled > 80% by pinoxaden and herbicide safeners did not reduce control. Field experiments should evaluate pinoxaden in combination with cloquintocet-mexyl and mefenpyr-diethyl to optimize safener : herbicide ratios and rates for creeping bentgrass safety as well as perennial ryegrass and roughtstalk bluegrass control in different climates and seasons. Nomenclature: Cloquintocet-mexyl; fenchlorazole-ethyl; mefenpyr-diethyl; pinoxaden; creeping bentgrass, Agrostis stolonifera L. AGSST; perennial ryegrass, Lolium perenne L. LOLPE; roughstalk bluegrass, Poa trivialis L. POATR