Aaron J. Patton

A Guide to Establishing Seeded Bermudagrass in the Transition Zone

Aaron J. Patton, Assistant Professor, Mike D. Richardson, Professor, and Doug E. Karcher, Associate Professor, Department of Horticulture, University of Arkansas, Fayetteville 72701; John W. Boyd, Professor, Crop, Soil & Environmental Science, University of Arkansas Cooperative Extension Service, Little Rock 72203; Zachary J. Reicher, Professor, Department of Agronomy, Purdue University, West Lafayette, IN 47907; Jack D. Fry, Professor, Department of Horticulture, Forestry, and Recreation Resources, Kansas State University, Manhattan, KS 66506; J. Scott McElroy, Assistant Professor, Department of Agronomy and Soils, Auburn University, Auburn, AL 36849; and Gregg C. Munshaw, Assistant Professor, Mississippi State University, Department of Plant and Soil Sciences, Mississippi State 39762

Safety of Herbicides on 'Zenith' Zoysiagrass Seedlings

Improved cultivars of zoysiagrass established by seed are now available, but little is known about the safety of herbicides on zoysiagrass seedlings. Our objective was to determine the turf safety of various herbicides when applied from emergence to 4 wk after emergence (WAE) of ‘Zenith’ zoysiagrass. Oxadiazon (3.4 kg ai/ha), MSMA (2.3 kg ai/ha), and pronamide (1.1 kg ai/ha) did not reduce coverage 7 WAE when applied at emergence or later and caused only temporary discoloration of seedlings. Foramsulfuron (0.03 kg ai/ha) injured seedling zoysiagrass both years of testing and reduced cover in the final year. Fluazifop (0.07 kg ai/ha) caused significant injury in all 3 yr of the study and reduced coverage in the final year. Fenoxaprop (0.14 kg ai/ha) caused visible injury and reduction in zoysiagrass coverage in all 3 yr of the study. Our studies indicate pronamide, MSMA, or oxadiazon are the safest herbicides to use over Zenith zoysiagrass seedlings, and selection among these three depends on the primary weed species present. Nomenclature: Fenoxaprop, fluazifop-P, foramsulfuron, MSMA, oxadiazon, pronamide, zoysiagrass, Zoysia japonica Steud. ‘Zenith’ ZOYJA

Potential Damage to Sensitive Landscape Plants from Wood Chips of Aminocyclopyrachlor Damaged Trees

Abstract Applications of aminocyclopyrachlor in 2011 to turf resulted in brown and twisted shoots, leaves, and needles; shoot dieback; and in some cases, death of trees and ornamental plants adjacent to treated turf areas. Our research objective was to determine if a sensitive plant could be injured from wood chips (mulch) obtained from aminocyclopyrachlor-damaged trees, and to quantify movement of aminocyclopyrachlor from contaminated wood chips into soil and its subsequent uptake by roots into landscape plant tissues. Tomatoes were grown under greenhouse conditions and mulched with chipped tree branches collected from honey locust and Norway spruce damaged 12 mo previously by aminocyclopyrachlor. Analysis of tomato tissue for aminocyclopyrachlor residues 32 d after mulching found aminocyclopyrachlor in all mulched tomato plants, which was consistent with observations of epinasty on tomato leaflets. Aminocyclopyrachlor residues ranged from 0.5 to 8.0 ppb in tomato plants while chipped tree branches contained 1.7 to 14.7 ppb. Aminocyclopyrachlor residues in the potting soil below the mulch ranged from below the quantifiable limit to 0.63 ppb, indicating that aminocyclopyrachlor can leach from wood chips into soil, causing plant injury. These results indicate that trees damaged by aminocyclopyrachlor should not be chipped and used for mulch or as an ingredient in compost. Nomenclature: Aminocyclopyrachlor; honey locust; Gleditsia triacanthos L.; Norway spruce; Picea abies (L.) Karst.; tomato; Solanum lycopersicum L. Resumen En 2011, aplicaciones de aminocyclopyrachlor en céspedes resultó en tejido aéreo y hojas café y enrolladas, muerte del tejido aéreo, y en algunos casos, la muerte de árboles y plantas ornamentales adyacentes a las áreas tratadas en el césped. El objetivo de nuestra investigación fue determinar si una planta sensible podría ser dañada por una cobertura de chips de madera (mulch) que se obtuvo a partir de árboles dañados con aminocyclopyrachlor, y cuantificar el movimiento de aminocyclopyrachlor desde chips de madera hacia el suelo y su subsiguiente absorción por las raíces de plantas presentes en el paisaje. Plantas de tomate fueron crecidas en invernadero y con cobertura de chips hecha a partir de ramas colectadas de árboles de Gleditsia triacanthos y Picea abies dañados 12 meses antes con aminocyclopyrachlor. El análisis de aminocyclopyrachlor en el tejido de tomate 32 d después de poner la cobertura encontró aminocyclopyrachlor en todas las plantas de tomate con cobertura, lo cual fue consistente con observaciones de epinastia en las hojas de tomate. Los residuos de aminocyclopyrachlor variaron entre 0.5 y 8.0 ppb en plantas de tomate mientras que en las ramas de los árboles fue de 1.7 a 14.7 ppb. Los residuos de aminocyclopyrachlor en la mezcla de suelo de las macetas debajo de la cobertura varió desde niveles por debajo del límite de cuantificación a 0.63 ppb, indicando que aminocyclopyrachlor puede lixiviarse desde los chips de madera al suelo, causando daño en las plantas. Estos resultados indican que árboles dañados con aminocyclopyrachlor no deberían ser usados para producir coberturas o como ingrediente en compost.

Bermudagrass and Zoysiagrass Cultivar Selection: Part 2, Divot Recovery

Golfers commonly remove turf and soil when swinging a golf club causing a divot in the turf. Divot recovery is an important factor that should be considered when selecting a species or cultivar for use on golf course tees or fairways. There are few reports directly comparing the divot recovery among bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia spp. Willd.) cultivars. Therefore, the objective of this experiment was to quantify divot recovery of several bermudagrass and zoysiagrass cultivars in a combined field experiment. Divot recovery was evaluated on four collection dates for five cultivars of bermudagrass and seven cultivars of zoysiagrass. Cultivars generally with the fastest time to 50% recovery were ‘Princess 77’ and ‘Riviera’ bermudagrass and ‘Palisades’ zoysiagrass. Generally, the cultivars with the slowest time to 50% recovery were ‘Meyer’ and ‘Zenith’ zoysiagrass. Additionally, ‘Tifway’ bermudagrass had similar divot recovery times to ‘El Toro’ and Palisades zoysiagrass. These results demonstrate that differences and similarities exist among bermudagrass and zoysiagrass cultivars for divot recovery, and golf course superintendents can use this information to better select cultivars that could improve surface playing conditions. Introduction A swing by a golfer while attempting to strike a golf ball commonly displaces an area of turf and soil that is referred to as a divot (7). Divots created by a golf stroke are a regular occurrence on golf course fairways or tees (7). It has been estimated that approximately 0.21 ha of turf are removed by divoting from a bermudagrass golf course fairway each year (7). The number, size, and length of time divots exist on a tee or fairway depend on species (1). Divot recovery describes the rate of recovery of a turfgrass from divoting and is an important factor that should be considered when selecting a species or cultivar for use on golf course tees or fairways and other athletic playing fields. There have been few studies to quantify differences in recovery rates between species, but popular turf textbooks (1,10) rank bermudagrass (Cynodon spp.) as having superior recuperative capacity or rate compared to zoysiagrass (Zoysia spp.). Karcher et al. (4,5) examined the divot recovery on native soil for numerous bermudagrass and zoysiagrass cultivars in separate field studies. Karcher et al. (4) reported that Riviera, Princess 77, and ‘Patriot’ bermudagrass each had relatively fast divot recoveries for the cultivars tested during the first year of the experiment. However, in the second year’s results, there were no differences among Princess 77, Riviera, Tifway, ‘Tifsport,’ and Patriot bermudagrass. In a separate study evaluating zoysiagrass cultivars, Karcher et al. (5) reported that Palisades, ‘Cavalier,’ Zenith, and ‘Zorro’ zoysiagrass all had similar divot recovery, while Meyer had a significantly slower divot recovery. El Toro had the fastest divot recovery in one year of the study, but had a relatively slower divot recovery in another year. Although bermudagrass and zoysiagrass were evaluated in separate experimental areas by Karcher et al. (4,5), their data 30 June 2011 Applied Turfgrass Science suggest that the recuperative capacity of these two species may not be as different as previously reported (1,10). For example, in 2004 Karcher et al. (4) reported that Riviera bermudagrass required 4.6 days to reach 50% recovery, while in 2004 Karcher et al. (5) reported that Palisades zoysiagrass required 4.2 days to reach 50% recovery. It has also been reported that zoysiagrass cultivars can differ greatly in growth rate and establishment rate (6), suggesting that some zoysiagrass cultivars may also have divot recovery similar to specific bermudagrass cultivars. Therefore, the objective of this experiment was to quantify the divot recovery for commonly used bermudagrass and zoysiagrass cultivars in the same experimental field trial. Evaluating Divot Recovery This experiment was conducted at the Arkansas Agricultural Research and Extension Center, in Fayetteville, AR (36°06’N, 94°10’W, 384 m). The planting site was fumigated with methyl bromide at 549 kg/ha in April 2007 and was a Captina silt-loam soil (fine-silty mixed mesic Typic Fragiudalt) with a pH of 6.6, 1% organic matter, 105 kg P/ha, and 97 kg K/ha. Five cultivars of bermudagrass and seven cultivars of zoysiagrass were evaluated in the experiment (Table 1). Cultivar selection was based on use and availability in the transition zone and southern United States. All cultivars were established as sod in July 2007 as 1.8m by 1.8-m plots with a 0.3-m border maintained with glyphosate (2.2 kg/ha) to prevent contamination from adjacent plots. Due to limited sod availability, ‘Diamond’ zoysiagrass was initially planted as 0.5-m by 0.5-m plots until additional plant material could be propagated. Diamond zoysiagrass plugs were planted in May 2008 in the remainder of the plot area and plots were > 95% cover by August 2008. To simulate golf course fairway conditions, all plots were mowed at 1.3 cm. The experimental design was a randomized complete block design with four replications. Plots were fertilized with nitrogen using urea (460-0) at 24 kg/ha per growing month for zoysiagrass and 49 kg/ha per growing month for bermudagrass based upon input from Arkansas golf course superintendents. Simazine was applied to all plots on 21 November 2007 and 24 November 2008 at 1.1 kg/ha to control winter annual weeds. An additional application of foramsulfuron was applied on 13 April 2008 at 30 g/ha to control annual bluegrass (Poa annua L.). Table 1. Cultivar, experimental notation, and species of bermudagrass and zoysiagrass used in this study to quantify divot recovery in Fayetteville, AR. x The cultivars Princess 77 bermudagrass and Zorro zoysiagrass were each evaluated using two experimental notations before the cultivars were released for commercial use. Cultivar Experimental

Bermudagrass and Zoysiagrass Cultivar Selection: Part 1, Clipping Yield, Scalping Tendency, and Golf Ball Lie

Bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia spp. Willd.) are two of the most commonly used turfgrass species on golf course fairways and tees in the southern United States. However, there are few reports directly comparing commonly used cultivars of bermudagrass to commonly used cultivars of zoysiagrass. The objectives of this research were to quantify the clipping yield, percent ball exposed (ball lie), and to identify the scalping tendency for five bermudagrass and seven zoysiagrass cultivars grown in Fayetteville, AR. The cultivars generally producing the lowest clipping yields were ‘Patriot’ bermudagrass and ‘Meyer’ zoysiagrass, while ‘Tifway’ bermudagrass and ‘Palisades’ zoysiagrass generally had the highest clipping yields. On most collection dates, Cynodon spp. yielded more clippings than Zoysia spp. Patriot bermudagrass had the highest scalping tendency across the two years of this study. The cultivars Patriot, ‘Riviera,’ ‘Tifsport,’ and Tifway bermudagrass as well as Meyer and Diamond zoysiagrass had the best ball lie in unmown (five days after mowing) conditions, while Palisades zoysiagrass had the poorest ball lie in unmown conditions. Ball lie was similar for all cultivars immediately following mowing. These studies identified cultivars of bermudagrass and zoysiagrass that have improved clipping yields, scalping tendencies, and golf ball lie. Introduction Bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) are the predominant turfgrass species used on golf course fairways and tees in Arkansas (30). Across the transition zone and southern United States, bermudagrass is the most commonly used turfgrass on fairways and tees (24), and bermudagrass and zoysiagrass are adapted to the transition and warm humid, climatic zones (4). Bermudagrass and zoysiagrass are desirable species for golf course fairways and tees due to their deep rooting, disease resistance, recovery potential, drought, heat, wear, traffic, and low mowing height tolerance (3,38,39,40). Several studies have reported differences of growth rate between bermudagrass and zoysiagrass. Patton et al. (31) determined that bermudagrass was faster to establish from seed than zoysiagrass. Volterrani et al. (41) and Busey and Myers (9) reported a faster vegetative establishment for bermudagrasses than zoysiagrasses. Trappe et al. (39) reported both similarities and differences in divot recovery for various bermudagrass and zoysiagrass cultivars. Several important aspects of golf course management can be influenced by growth rate, including clipping yield, scalping tendency, and golf ball lie (6,11,16). Differences in growth rate have been reported between bermudagrass and zoysiagrass (6,13,14). Beard et al. (6) reported variations in leaf extension rates among bermudagrass genotypes, and concluded that this variation would 30 June 2011 Applied Turfgrass Science require adjustment of mowing frequency between cultivars. Although some reports (6,13,14) document differences in leaf extension rates of species or cultivars, other work (21) shows little difference among species or cultivars. Kim and Beard (21) investigated the vertical leaf extension rate of ‘Arizona Common’ bermudagrass, Tifway bermudagrass, and Meyer zoysiagrass in the greenhouse and reported no differences among these cultivars. However, more research is needed comparing clipping yields for commonly used cultivars of bermudagrass and zoysiagrass. Species or cultivars that require less maintenance, such as reduced mowing frequency, are becoming more desirable to turfgrass managers (33). Research documenting differences in clipping yield among cultivars and species would allow superintendents to choose a cultivar that could facilitate a reduced frequency for mowing and possibly reduced use of plant growth regulators. These cultivars could help to reduce equipment wear, labor, and fuel costs associated with maintaining golf course fairways and tees or sports fields. Scalping has been defined as “the removal of an excessive quantity of green shoots from a turf at any one mowing that results in a stubby, brown appearance due to the exposed stems, stolons, and dead lower leaves” (5). While Beard and Beard (5) cite the aesthetic damage scalping incurs on a turfgrass sward, it can also affect plant health (1,8,29,34). Faster growth rates of some species and cultivars increase thatch production, which could promote scalping (11). In addition to excessive thatch accumulation, other potential causes of scalping may include mower adjustment errors, infrequent mowing, or an uneven soil surface (10). In general, scalping also disrupts a consistent playing surface that is necessary for golfing. Differences in bermudagrass and zoysiagrass cultivar susceptibility to scalping have been reported. Across two locations rating for bermudagrass scalping tendency, Patriot was rated to be the most susceptible to scalping, with ‘Princess 77’ and Tifway having moderate scalping damage and Riviera and Tifsport as having minimal scalping (28). In a separate study evaluating scalping tendency of zoysiagrass cultivars in California, ‘Zenith’ was more susceptible to scalping than El Toro, Meyer, and ‘Zorro’ in May and June but similar in scalping tendency in other months (27). Hale (15) reported that ‘Royal’ and ‘Cavalier’ zoysiagrass were more prone to scalping under higher rates of N (≥ 192 kg/ha/year). These works evaluated scalping tendency within species. However, little research has evaluated scalping tendency among multiple species. The position at which a golf ball comes to rest in a turf canopy influences how a golfer will attempt their next shot. A golf ball that rests on top of the canopy provides golfers increased control over golf shots (23). Beard (4) cited turfgrass species, cultivar, and shoot density as determining factors for ball lie. Others have also stated zoysiagrass provides a good golf ball lie for players to take their shot (7,17). Researchers at the University of Arkansas recently developed a method to measure golf ball lie using digital image analysis (36). Little differences among cultivars of bermudagrass and zoysiagrass were reported for plots mown at 1.25 cm, but some differences in golf ball lie were observed for plots mown at 2.5 cm (36). Other work has evaluated the specific management practices that affect ball lie in bermudagrass (16,25), but none have attempted to quantify differences in ball lie among bermudagrass and zoysiagrass cultivars. There are few reports comparing commonly used cultivars of bermudagrass to commonly used cultivars of zoysiagrass and a need exists to evaluate cultivars across species in direct comparison experiments. The objectives of this research were to: (i) quantify clipping yield; (ii) identify scalping tendency; and (iii) quantify golf ball lie for several bermudagrass and zoysiagrass cultivars commonly used on golf course fairways and tees. Evaluating Clipping Yield, Scalping Tendency, and Golf Ball Lie This experiment was conducted at the Arkansas Agricultural Research and Extension Center, in Fayetteville, AR (36°06’N, 94°10’W, 384 m). The planting site was fumigated with methyl bromide at 549 kg/ha on 17 April 2007 and was 30 June 2011 Applied Turfgrass Science a Captina silt-loam soil (fine-silty mixed mesic Typic Fragiudalt) with a pH of 6.6, 1% organic matter, 105 kg P/ha, and 97 kg K/ha. Five cultivars of bermudagrass and seven cultivars of zoysiagrass were used in the experiment (Table 1). Cultivar selection was based on use and availability in the transition zone and southern United States. All cultivars were established as sod in July 2007 as 1.8-m by 1.8-m plots with a 0.3-m border maintained to prevent contamination from adjacent plots. Due to limited sod availability, ‘Diamond’ zoysiagrass was initially planted as 0.5-m by 0.5-m plots until additional plant material could be propagated. Diamond plugs were planted in May 2008 in the remainder of the plot area and plots were fully established by August 2008. Table 1. Cultivars, experimental notation, and species of bermudagrass and zoysiagrass used in this study. * The cultivars Princess 77 bermudagrass and Zorro zoysiagrass were each evaluated using two experimental notations before the cultivars were released for commercial use. Cultivar Experimental notation Species Cavalier DALZ8507 Zoysia matrella (L.) Merr. Diamond DALZ8502 Zoysia matrella (L.) Merr. El Toro UCR#1 Zoysia japonica Steud. Meyer Z-52 Zoysia japonica Steud. Palisades DALZ8514 Zoysia japonica Steud. Patriot PKC 18-4 Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy Princess 77 FMC-77, SWI-77* Cynodon dactylon (L.) Pers. var. dactylon Riviera OKS 95-1 Cynodon dactylon (L.) Pers. var. dactylon Tifsport Tift 94 Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy Tifway Tifton 419 Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy Zenith ZNW-1 Zoysia japonica Steud. Zorro DALZ8510, DALZ9601* Zoysia matrella (L.) Merr. All experimental areas were maintained under typical golf course fairway conditions, with a mowing height of 1.3 cm. All plots were fertilized with nitrogen using urea (46-0-0) at 24 kg/ha per growing month for zoysiagrass and 49 kg/ha per growing month for bermudagrass based on input from Arkansas golf course superintendents. The experimental design was a randomized complete block design with four replications. Clipping yield was measured on 4 and 28 August and 23 September 2008 as well as on 4 June, 13 July, and 31 August 2009. The area of each plot from where clippings were collected was measured prior to each collection and recorded to provide a total dry weight per unit area measurement. A Jacobsen Greensking (Textron Co., Charlotte, NC) mower was used to collect clippings and two passes (opposite directions) were made on the same area of the plot to ensure complete clipping collection. Clippings were collected when all plots grew to a height of at least 1.9 cm, w

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.

Sulfonylurea herbicide safety on newly sprigged bermudagrass and seashore paspalum.

Abstract Several sulfonylurea herbicides are labeled for use on established bermudagrass or seashore paspalum, but label recommendations for many of these chemicals vary for sprigged turf. The objective of this study was to determine the safety of various sulfonylurea herbicides on newly planted, ‘Tifway’ bermudagrass and ‘Aloha’ seashore paspalum sprigs in Arkansas and Louisiana. Treatments were arranged as a five by two by two factorial with five herbicides (foramsulfuron at 29 and 59 g ai ha−1, halosulfuron at 35 and 70 g ai ha−1, metsulfuron at 21 and 42 g ai ha−1, sulfosulfuron at 66 and 131 g ai ha−1, and trifloxysulfuron at 28 and 56 g ai ha−1), two herbicide rates (low and high), and two application timings at 2 or 4 wk after sprigging (WAS). There was no discernable herbicide injury to, or reduction in, Tifway bermudagrass coverage in Arkansas, regardless of herbicide, application timing, or application rate. Trifloxysulfuron and metsulfuron were more injurious than other herbicides in Louisiana when applied at 2 WAS to Tifway bermudagrass, but injury levels were acceptable (< 15%), and there was no long-term reduction in establishment. Metsulfuron or halosulfuron applied at 2 or 4 WAS and sulfosulfuron applied at 4 WAS allowed > 90% establishment of Aloha seashore paspalum at both locations. Both trifloxysulfuron and foramsulfuron were injurious to seashore paspalum and reduced its establishment. These results suggest that sulfonylurea herbicides can be safely applied shortly after sprigging to Tifway bermudagrass and that metsulfuron, halosulfuron, and sulfosulfuron could be useful herbicides for establishing Aloha seashore paspalum from sprigs. Nomenclature: Foramsulfuron; halosulfuron; metsulfuron; sulfosulfuron; trifloxysulfuron; hybrid bermudagrass, Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy ‘Tifway’ CYNDA; seashore paspalum, Paspalum vaginatum Sw. ‘Aloha’ PASVA.

Divalent Cations in Spray Water Influence 2,4-D Efficacy on Dandelion (Taraxacum officinale) and Broadleaf Plantain (Plantago major)

2,4-dichlorophenoxyacetic acid (2,4-D) is a common ingredient in POST broadleaf herbicides labeled for use in turf, pastures, rangeland, and grain crops. The herbicide 2,4-D is a weak acid, and when dissociated can bind to cations present in hard-water spray solutions and/or fertilizer solutions. Experiments were conducted with 2,4-D dimethylamine to evaluate the effect of cation solutions on herbicide efficacy on the perennial broadleaf weeds dandelion and broadleaf plantain. The objectives of this research were to (1) determine if 2,4-D efficacy is influenced by the divalent cations, calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) in spray solution; and (2) determine if adding the adjuvant ammonium sulfate (AMS) to the spray solution can overcome antagonism. Broadleaf plantain and dandelion control was reduced and plant size and mass increased when 2,4-D was applied in a Ca solution in comparison to deionized water. However, 2,4-D antagonism was overcome when AMS was added as an adjuvant to the spray solution. Magnesium caused 2,4-D antagonism on both weed species in one run of the experiment similar to Ca solution and AMS was successful at overcoming antagonism when added to the tank mixture. Some 2,4-D antagonism from Mn was noticed even when AMS was in the tank mix, but Zn fertilizer solutions did not antagonize 2,4-D activity on either weed species. Although divalent cations can antagonize 2,4-D dimethylamine and reduce perennial broadleaf weed control, adding AMS can overcome this antagonism when Ca and Mg are the primary cations in spray solution. Applicators should avoid using Mn fertilizers when applying 2,4-D dimethylamine because AMS did not successfully overcome antagonism. Nomenclature: 2,4-D; broadleaf plantain, Plantago major L., PLAMA; dandelion, Taraxacum officinale G. H. Weber ex Wiggers, TAROF. 2,4-dichlorophenoxyacetic acid (2,4-D) es un ingrediente común en herbicidas POST para el control de malezas de hoja ancha registrados para su uso en céspedes, pasturas, y cultivos de granos. El herbicida 2,4-D es un ácido débil, y cuando este se disocia puede adherirse a cationes presentes en soluciones de aspersión con aguas pesadas y/o soluciones con fertilizantes. Se realizaron experimentos de campo con 2,4-D dimethylamine para evaluar el efecto de soluciones con cationes en la eficacia del herbicida para el control de las malezas perennes de hoja ancha Taraxacum officinale y Plantago major. Los objetivos de esta investigación fueron (1) determinar si la eficacia de 2,4-D es influenciada por los cationes divalentes calcium (Ca), magnesium (Mg), manganese (Mn), y zinc (Zn) en la solución de aspersión; y (2) determinar si el agregar el adyuvante ammonium sulfate (AMS) a la solución de aspersión puede reducir el antagonismo. El control de P. major y T. officinale se redujo y el tamaño y masa de planta aumentó cuando 2,4-D fue aplicado en una solución de Ca en comparación con agua desionizada. Sin embargo, el antagonismo con el 2,4-D fue reducido cuando se agregó AMS como adyuvante para la solución de aspersión. Magnesium causó antagonismo con 2,4-D en ambas especies de malezas en una de las corridas experimentales, la cual fue similar a la solución de Ca y AMS fue exitoso en reducir el antagonismo cuando se agregó a la mezcla en tanque. Se notó un poco de antagonismo entre 2,4-D y Mn inclusive cuando AMS estuvo en la mezcla en tanque, pero las soluciones de Zn no antagonizaron la actividad del 2,4-D en ninguna de las especies. Aunque los cationes divalentes pueden antagonizar al 2,4-D dimethylamine y reducir el control de malezas perennes de hoja ancha, el agregar AMS puede reducir este antagonismo cuando Ca y Mg son los cationes primarios en la solución de aspersión. Los aplicadores deberían evitar usar fertilizantes con Mn cuando apliquen 2,4-D dimethylamine porque AMS no reducirá exitosamente el antagonismo.

2,4-D–Resistant Buckhorn Plantain (Plantago lanceolata) in Managed Turf

Abstract A population of buckhorn plantain with suspected resistance to 2,4-D was identified in central Indiana following 30 yr of 2,4-D-containing herbicide applications. Our objectives were to (1) confirm and quantify the level of herbicide resistance in the buckhorn plantain population using dose-response experiments and (2) find alternative herbicides that could be used to control this population. Greenhouse experiments were conducted to quantify the dose-response of resistant (R) and susceptible (S) biotypes of buckhorn plantain to both 2,4-D and triclopyr, two synthetic auxin herbicides from different chemical families. The R biotype was ≥6.2 times less sensitive to 2,4-D than the S biotype. The efficacy of triclopyr was similar on both the R and S biotypes of buckhorn plantain, suggesting the absence of cross-resistance to this herbicide. This is the first report of 2,4-D resistance in buckhorn plantain and the first report of 2,4-D resistance in turf. The resistance mechanism was limited to within a chemical family (phenoxycarboxylic acid) and did not occur across all WSSA Group 4 synthetic auxin herbicides, as the pyridinecarboxylic acid herbicides clopyralid and triclopyr and the arylpicolinate herbicide halauxifen-methyl provided control in our experiments. Nomenclature: 2,4-D, clopyralid, halauxifen-methyl, triclopyr, buckhorn plantain, Plantago lanceolata L. PLALA

Mesotrione Activity on Crabgrass (Digitaria spp.) as Influenced by Nitrogen Fertilization Rate, Source, and Timing

Abstract Mesotrione, a 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide, is labeled for PRE and POST crabgrass control. It has enhanced efficacy on smooth and large crabgrass when applied in conjunction with soil-applied nitrogen (N). The objectives of this study, using crabgrass as the weed species, were to (1) determine the influence of N rate and tissue N concentration on mesotrione activity, (2) determine the influence of N source on mesotrione activity, and (3) determine the influence of N application timing on mesotrione activity. Large crabgrass plants that received 12 kg N ha−1 or more before mesotrione application had more bleached and necrotic leaves compared with plants that received 0 kg N ha−1 7 d after treatment (DAT) in the greenhouse. Although N application rates as high as 98 kg N ha−1 were tested, 90% leaf bleaching and necrosis were observed with rates of 8.9 or 10.1 kg N ha−1 in Tennessee and Indiana, respectively. Nitrogen concentration in large crabgrass leaf and stem tissue on the day of the mesotrione application was closely related to the bleaching and necrosis symptoms observed 7 DAT. Although N rate influenced mesotrione activity, N source did not. Nitrogen application timing was also important, with N applications 3, 1, and 0 d before a mesotrione application having the highest percentage of bleached and necrotic leaves in greenhouse experiments. Both greenhouse and field trials support the finding that N applications in proximity to the mesotrione application enhance herbicide activity. Thus, practitioners can pair N and POST mesotrione applications together or in proximity to enhance crabgrass control. Nomenclature: Mesotrione; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; smooth crabgrass, Digitaria ischaemum (Schreb.) Schreb. ex Muhl. DIGIS. Resumen Mesotrione es un herbicida inhibidor de 4-hydroxyphenylpyruvate dioxygenase que está registrado para el control PRE y POST de especies del género Digitaria. Tiene una actividad mayor en Digitaria ischaemum y Digitiaria sanguinalis cuando se aplica en forma conjunta con nitrógeno aplicado al suelo (N). Los objetivos de este estudio, enfocándose en Digitaria, fueron: (1) determinar la influencia de la dosis de N y la concentración de N en el tejido sobre la actividad de mesotrione, (2) determinar la influencia de la fuente de N sobre la actividad de mesotrione, y (3) determinar la influencia del momento de aplicación de N sobre la actividad de mesotrione. Plantas de D. sanguinalis que recibieron 12 kg N ha−1 o más antes de la aplicación de mesotrione, tuvieron más hojas blanqueadas y necróticas que las plantas que recibieron 0 kg N ha−1 a 7 d después del tratamiento (DAT), en el invernadero. Aunque se evaluaron dosis de aplicación de N de hasta 89 kg N ha−1, con dosis de sólo 8.9 ó 10.1 kg N ha−1 se observó 90% blanqueamiento y necrosis foliar, en Tennessee e Indiana, respectivamente. La concentración de N en el tejido foliar y del tallo de D. sanguinalis, el día de la aplicación de mesotrione, estuvo altamente relacionada a los síntomas de blanqueamiento y necrosis observados a 7 DAT. Aunque la dosis de N influenció la actividad de mesotrione, la fuente de N no lo hizo. El momento de aplicación de N también fue importante. Así, las aplicaciones de N a 3, 1, y 0 d antes de la aplicación de mesotrione tuvieron el mayor porcentaje de hojas blanqueadas y necróticas en experimentos de invernadero. Tanto los estudios de invernadero como los de campo apoyan los resultados de que aplicaciones de N cercanas a la aplicación de mesotrione mejoran la actividad del herbicida. De esta forma, los usuarios pueden combinar aplicaciones de N y mesotrione POST o realizarlas en momentos cercanos para mejorar el control de malezas del género Digitaria.