Weeks After Initial Treatment Research Articles

Impact of Verticutting on the Efficacy and Soil Activity of ALS-inhibiting Herbicides for Dallisgrass Control

Dallisgrass (Paspalum dilatatum Poir.) control with postemergence herbicides is inefficient and inconsistent from year to year. Control with acetolactate synthase (ALS)-inhibiting herbicides may be enhanced through root absorption, but herbicide movement through dense turfgrass canopies may be difficult. The objectives of this research were to evaluate the influence of verticutting on the postemergence control of dallisgrass and the presence of ALS-inhibiting herbicides within the soil profile. Long-term dallisgrass control [17 weeks after initial treatment (WAIT)] was enhanced in response to verticutting at one of two locations. This may be attributed to differences in turfgrass management (mowing height) before trial initiation that impacted dallisgrass carbohydrate content and herbicide absorption. However, dallisgrass control with certain herbicides was enhanced at the second location in response to verticutting at earlier rating dates. Thiencarbazone + foramsulfuron + halosulfuron (TFH) and trifloxysulfuron at 112 g·ha−1 a.i. and carrier volume of 1628 L·ha−1 (TRI High CV) following mowing + verticutting resulted in the greatest long-term control 17 WAIT at one of two trial locations, 86% and 85%, respectively. Greenhouse experiments confirmed that mowing + verticutting dallisgrass before treatment followed by irrigation led to an increase in herbicide presence within the soil profile, regardless of herbicide. Presence of TFH went from 6.4 to 8.2 mm, trifloxysulfuron at 28 g·ha−1 a.i. and carrier volume of 407 L·ha−1 went from 6.7 to 8.5 mm, and TRI High CV went from 8.6 to 11.8 mm.

Evaluation of Sulfentrazone Alone or in Combination with Other PRE and POST Herbicides for Weed Control in Tomato (Solanum lycopersicum) and Strawberry (Fragaria ×ananassa)

Sulfentrazone was recently registered for use in tomato and strawberry in Florida. Field experiments were conducted at the Gulf Coast Research and Education Center in Wimauma, FL, to evaluate PRE sulfentrazone applications when applied on flat soil 30 days before bed formation (PRE-f), on the bed top immediately before laying plastic mulch (PRE-t), applied PRE-t as a tank mix with other PRE herbicides, or PRE-t followed by POST halosulfuron or rimusulfuron (POST). Sulfentrazone did not damage the tomato and strawberry crop and had no effect on strawberry and tomato fruit yield. It was as effective as the industry standards but none of the evaluated herbicide treatments provided adequate weed control. POST halosulfuron in tomato resulted in significantly greater nutsedge control at 11 (14%) and 13 (27%) weeks after initial treatment (WAIT) compared with other treatments in Fall 2019 and Spring 2020, respectively. However, in tomato, tank-mixing sulfentrazone with S-metolachlor or metribuzin did not enhance nutsedge control. Weed control did not improve with increased rates or with the use of PRE-f followed by (fb) PRE-t applications in tomato. PRE-t sulfentrazone fb POST halosulfuron was an efficient nutsedge management option in tomato. Sulfentrazone alone did not effectively control weeds in tomato or strawberry. Increased rates of sulfentrazone with the use of PRE-f fb PRE-t sulfentrazone applications did reduce (34%) total weed density in strawberry.

Mesotrione and Amicarbazone Tank-mixtures for Annual Bluegrass (Poa annua) Control in Cool-season Turfgrass

Annual bluegrass (Poa annua L.) control with postemergence herbicides in cool-season turfgrass is often inconsistent. Amicarbazone and mesotrione have complementary modes of action but have not been evaluated in tank-mixtures for control of mature annual bluegrass in cool-season turfgrass. Field experiments were conducted during 2018 in New Jersey, and in Indiana, Iowa, and New Jersey during 2019 to evaluate springtime applications of amicarbazone and mesotrione for POST annual bluegrass control in cool-season turfgrass. On separate tall fescue (Festuca arundinacea Schreb.) and kentucky bluegrass (Poa pratensis L.) sites in 2018, three sequential applications of amicarbazone (53 g⋅ha−1) + mesotrione at 110 to 175 g⋅ha−1 provided >70% annual bluegrass control, whereas three sequential applications of amicarbazone alone at 53 and 70 as well as two sequential applications at 110 g⋅ha−1 provided <15% control at 14 weeks after initial treatment (WAIT). In 2019, results in New Jersey were similar to 2018 where amicarbazone alone provided less control than mesotrione + amicarbazone tank-mixtures. In Indiana, where the annual bluegrass infestation was severe and most mature, tank-mixtures were more effective than amicarbazone alone at 6 WAIT, but at 12 WAIT all treatments provided poor control. In Iowa, where the annual bluegrass infestation was <1 year old, all treatments provided similar control throughout the experiment and by >80% at the conclusion of the experiment. This research demonstrates that sequential applications of mesotrione + amicarbazone can provide more annual bluegrass control than either herbicide alone, but efficacy is inconsistent across locations, possibly due to annual bluegrass maturity and infestation severity.

Selective perennial ryegrass control in creeping bentgrass with flazasulfuron

ABSTRACTLolium perenne L. (perennial ryegrass) commonly contaminates Agrostis stolonifera L. (creeping bentgrass) on cool‐season golf courses. Currently, few herbicide options are available for the selective control of L. perenne in A. stolonifera. Previous studies have indicated that flazasulfuron could be a potential solution, so trials were conducted at three sites in Blacksburg, VA to evaluate flazasulfuron rates and sequential treatments for L. perenne control and A. stolonifera response. Flazasulfuron applied once at 8.8 g a.i. ha−1; twice at 1.1, 2.2, and 4.4 g a.i. ha−1; and three times at 1.1 and 2.2 g a.i. ha−1 completely controlled L. perenne by 5 weeks after initial treatment (WAIT). Sulfosulfuron and bispyribac‐sodium controlled L. perenne 68 and 35% 5 WAIT, respectively. All flazasulfuron treatments eliminated L. perenne cover, sulfofulfuron reduced cover from 34 to 11% at one site, and bispyribac‐sodium did not influence cover 9 WAIT. All treatments generally caused up to 10% A. stolonifera injury within one week of each treatment but only flazasulfuron at 4.4 g a.i. ha−1 and sulfosulfuron caused unacceptable and persistent injury. Flazasulfuron applied in sequence at rates of ≤2.2 g a.i. ha−1 causes mild and transient discoloration of A. stolonifera but completely controls L. perenne.

Tropical Signalgrass Control in Seashore Paspalum

Tropical signalgrass (Urochloa subquadripara) is a mat-forming grass with relatively coarse texture. It is characterized by hairy sheaths and leaf blades plus a short fringe of hair present on the ligule. Tropical signalgrass control in Florida has been challenging for turf managers, in part, due to monosodium methanearsonate (MSMA) restrictions. Previous research indicates fall herbicide applications to be more effective than summer applications; however, fall applications typically do not allow turfgrass adequate time to fill in bare spots prior to winter. Two studies were conducted on seashore paspalum (Paspalum vaginatum) roughs at The Oaks golf course in Osprey, FL in summer 2019 comparing single and combination treatments of amicarbazone, carfentrazoneethyl, sulfentrazone, flazasulfuron, and quinclorac for control of tropical signalgrass. All treatments were applied with a non-ionicsurfactant at 0.25% v/v. In both studies a sequential application of each treatment was made 21 days after initial treatment (DAIT). Rating dates were 4 June, 25 June, 16 July, and 13 August, corresponding to 0, 21, 42, and 70 DAIT, respectively. In study one, 10 weeks after initial treatment (WAIT), amicarbazone + carfentrazone-ethyl + sulfentrazone at 0.23 + 0.0076 + 0.068 lb ai/acre (0.26 + 0.0085 + 0.076 kg ai/ha), respectively, provided best control (~60%). For study two, at 6 and 10 WAIT, tropical signalgrass control of >50% was not achieved. Overall, long-term postemergence control of tropical signalgrass with summer applications of herbicides tested was incomplete, even with multiple applications; however, amicarbazone + carfentrazone-ethyl + sulfentrazone showed potential as a control option.

Postemergence Weed Control in Warm-season Turfgrass with a Mixture of Pyrimisulfan and Penoxsulam

Pyrimisulfan is a sulfonanilide herbicidal inhibitor of acetolactate synthase (ALS) used to control grass and sedge weeds of rice (Oryza stricta L.) production. Penoxsulam is an ALS-inhibiting herbicide that provides early postemergence control of broadleaf weeds in managed turfgrass. Separate field trials were conducted in Knoxville, TN, during Summer 2017 and 2018 to evaluate the efficacy of pyrimisulfan + penoxsulam for control of white clover (Trifolium repens L.), yellow nutsedge (Cyperus esculentus L.), wild violet (Viola spp.), ground ivy (Glechoma hederacea L.), and virginia buttonweed (Diodia virginiana L.) in common bermudagrass (Cynodon dactylon L.) and tall fescue (Festuca arundinacea Schreb.) turf. All treatments were applied on a granular fertilizer carrier (mean particle size, 1.5 mm) that contained 21% N : 0% P2O5 : 3% K2O. Treatments were applied at an early postemergence growth stage during April of each year and were irrigated into the soil within 24 hours of application. Weed control was assessed from 4 to 10 weeks after initial treatment (WAIT) relative to untreated control plots in each replication. White clover and wild violet were controlled effectively with pyrimisulfan + penoxsulam at 70 + 70 g·ha−1 whereas sequential applications at either 70 + 70 g·ha−1 followed by 35 + 35 g·ha−1 or 52.5 + 52.5 g·ha−1 followed by 52.5 + 52.5 g·ha−1 were needed to control yellow nutsedge, ground ivy, and virginia buttonweed effectively. Future research should explore long-term control of these species, particularly wild violet, ground ivy, and virginia buttonweed with pyrimisulfan + penoxsulam applied over multiple seasons. Chemical names: 2′-[(4,6-dimethoxypyrimidin-2-yl)(hydroxy) methyl]-1,1-difluoro-6′-(methoxymethyl)methanesulfonanilide (pyrimisulfan); 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy1,2,4triazolo 1.5-c-pyrimidin-2-yl)-6-(trifluoromethyl)benzenesulfonamide (penoxsulam).

Postemergence Control and Glyphosate Tolerance of Doveweed (Murdannia nudiflora)

Doveweed is a problematic weed of lawns and sod production, as well as golf course roughs, fairways, and tees. End-user reports of selective POST control options are inconsistent and control is often short-lived. In addition, inconsistent control with non-selective herbicides such as glyphosate is common. The goals of this research were: (1) evaluate selective POST doveweed control options in ‘Tifway’ hybrid bermudagrass turf; (2) compare efficacy of single vs. sequential applications of selective POST herbicides; (3) quantify doveweed tolerance to glyphosate; and (4) quantify recovery of foliar applied glyphosate following treatment with a C14-glyphosate solution. A single application of sulfentrazone+metsulfuron; thiencarbazone+iodosulfuron+dicamba or 2,4-D+MCPP+dicamba+carfentrazone; or thiencarbazone+foramsulfuron+halosulfuron provided >60% control 2 weeks after initial treatment (WAIT). A second application of these treatments 3 WAIT improved control 6 WAIT. Two applications of 2,4-D+MCPP+dicamba+carfentrazone or thiencarbazone+foramsulfuron+halosulfuron provided ~80% control 6 WAIT. Doveweed was tolerant to glyphosate application up to 5.68 kgaeha-1. Absorption of 14C-glyphosate was compared between doveweed with cuticle intact, doveweed with a disturbed cuticle, and smooth crabgrass. 14C-glyphosate recovery from the leaf surface of doveweed plants with an intact cuticle was 93.6%. In comparison, 14C-glyphosate recovery from the leaf surface of doveweed plants with a disrupted cuticle and the leaf surface of crabgrass plants was 79.1 and 70.5%, respectively.

Herbicide Applications and Incorporation Methods Affect Dazomet Efficacy on Bermudagrass

Turfgrass renovations commonly involve changing cultivars or species that are better suited for a given setting. Common bermudagrass [Cynodon dactylon (L.) Pers.] is a perennial turfgrass that is difficult to eradicate before renovations, and poses contaminant concerns for the subsequent stand. Dazomet is a granular soil fumigant that has activity on various pests, including common bermudagrass. Field research was conducted from 2015 to 2016 in Raleigh, NC and College Station, TX to evaluate dazomet treatments including various combinations of soil incorporation (irrigation- or tillage-incorporated) and sealing (tarp or no tarp) methods, application rates [291, 291 followed by (fb) 291, 468, or 583 kg·ha−1], and fluazifop-P [fluazifop (0.4 kg·ha−1)] + glyphosate (2.8 kg·ha−1 acid equivalent) application(s) for established common bermudagrass control. Overall, treatments required fluazifop + glyphosate before dazomet application for acceptable control (>90% cover reduction) at 42 and 46 weeks after initial treatment (WAIT) in Texas and North Carolina, respectively. Soil-incorporation results varied by location, with dazomet application (583 kg·ha−1) fb tillage resulting in ≥88% cover reduction across locations, while acceptable control from irrigation incorporation was only observed in North Carolina. Tarping did not improve efficacy when tillage incorporation at the maximum label application rate provided acceptable control, suggesting practitioners may eliminate this procedure. Information from this research will aid turfgrass managers in developing cost-effective, ecologically sound common bermudagrass eradication programs before renovations.

Efficacy of Metamifop for the Control of Common Bermudagrass

Metamifop is a postemergence aryloxyphenoxypropionic acid herbicide used for the control of annual and perennial grass weeds in cereal crops and rice (Oryza sativa L.). Previous research observed creeping bentgrass (Agrostis stolonifera L.) tolerance to applications of metamifop, suggesting utilization for the removal of encroaching bermudagrass (Cynodon Rich.) from creeping bentgrass putting greens with little to no phytotoxicity. Therefore, the objective of our research was to evaluate the efficacy of metamifop for common bermudagrass [Cynodon dactylon (L.) Pers.] control in a greenhouse environment. Experiments were conducted at the Plant and Soil Science greenhouse facility at Texas Tech University in Lubbock in 2011 and 2012. ‘Riviera’ and ‘Savannah’ common bermudagrass were seeded at 218 lb/acre into 4-inch square pots containing a soilless potting media on 26 Aug. 2011 and 14 Nov. 2011. Pots were allowed to mature in the greenhouse over a 3-month period where they were maintained at a height of 0.25 inches. Herbicide treatments were applied on 1 Dec. 2011 and 8 Feb. 2012 and consisted of metamifop at 0.18, 0.27, 0.36, or 0.45 lb/acre. A sequential application of each treatment was made on 22 Dec. 2011 and 29 Feb. 2012. A nontreated control was included for comparison. Clipping ceased after initial herbicide treatment and pots produced biomass for 3 weeks. Biomass above 0.25 inch was removed from each pot, dried, and weighed. This procedure was conducted again 3 weeks after sequential treatments. The rate of metamifop required to reduce bermudagrass growth 50% (GR50) was calculated 3 and 6 weeks after initial treatment (WAIT). Visual ratings of percent bermudagrass control were recorded weekly on a scale of 0% (no control) to 100% (completely dead bermudagrass). As metamifop rate increased, bermudagrass biomass decreased. The calculated GR50 at 3 WAIT for ‘Savannah’ and ‘Riviera’ was 0.19 and 0.14 lb/acre, respectively. Nontreated control pots exhibited 0% control and produced 0.59 to 0.83 g of biomass at 3 WAIT, regardless of cultivar. Metamifop at 0.27 to 0.45 lb/acre exhibited 96% to 100% bermudagrass control at 3 WAIT, regardless of cultivar. Bermudagrass subjected to those same treatments only produced 0.01 to 0.03 g of biomass at 3 WAIT, regardless of cultivar. The 0.18-lb/acre rate of metamifop exhibited only 9% control of ‘Savannah’ bermudagrass with 0.72 g of biomass collected, while ‘Riviera’ was controlled 41% with 0.38 g of biomass collected. The calculated GR50 at 6 WAIT for ‘Savannah’ and ‘Riviera’ was 0.13 and 0.14 lb/acre, respectively. Sequential applications of metamifop at 0.27 to 0.45 lb/acre completely controlled bermudagrass (100%) at 6 WAIT, while a sequential application at 0.18 lb/acre only controlled bermudagrass 8% to 19% at 6 WAIT, regardless of cultivar. Bermudagrass subjected to 0.18 lb/acre exhibited 0.48 to 0.56 g of biomass at 6 WAIT, regardless of cultivar. Metamifop shows potential as an alternative control option for common bermudagrass present within cool-season turfgrass species.

Dallisgrass (Paspalum dilatatum) Control with Thiencarbazone-methyl, Foramsulfuron, and Halosulfuron-methyl in Bermudagrass Turf

Dallisgrass control in response to various timings and frequencies of single and combination herbicide treatments was evaluated from 2010 to 2012 in Lubbock, TX. Treatments included thiencarbazone-methyl + foramsulfuron + halosulfuron-methyl (TFH) at 15 + 31 + 47 or 22 + 45 + 70 g a.i./ha, foramsulfuron at 106 g a.i./ha, and foramsulfuron + thiencarbazone-methyl + iodosulfuron-methyl-sodium + dicamba (foramsulfuron + TID) at 106 + (22 + 5 + 147) g a.i./ha. Applications of TFH provided ≤65% dallisgrass control by 10 weeks after initial treatment (WAIT) across two rates (15 + 31 + 47 or 22 + 45 + 70 g a.i./ha) and three application timings [September, October, or September followed by (fb) a sequential October application]. At 37 WAIT, sequential applications of TFH at 15 + 31 + 47 g a.i./ha resulted in 92% dallisgrass control. Similarly, application of TFH at 22 + 45 + 70 g a.i./ha provided 94% and 97% dallisgrass control when applied in September or September fb October, respectively. However, single October applications of TFH only provided ≤55% dallisgrass control 37 WAIT. Sequential combinations of foramsulfuron + TID at 106 + (22 + 5 + 147) g a.i./ha provided 93% dallisgrass control 37 WAIT, equivalent to single applications of TFH at 15 + 31 + 47 g a.i./ha and sequential treatments at 15 + 31 + 47 or 22 + 45 + 70 g a.i./ha. However, initial control (10 WAIT) with foramsulfuron + TID was moderate (63%). Sequential foramsulfuron applications (106 g a.i./ha) resulted in inadequate dallisgrass control (35% and 48%) 10 and 37 WAIT, respectively. Results from this study suggest that long-term dallisgrass control may be achieved when TFH is applied in September or September fb October. Applications initiated in October resulted in inadequate control, regardless of rate, which may be linked to reduced herbicidal absorption and translocation due to the onset of dallisgrass dormancy in late fall. Chemical names used: methyl 4-[(4,5-dihydro-3-methoxy-4-methyl-5-oxo-1H-1,2,4-triazol-1-yl)carbonylsulfamoyl]-5-methylthiophene-3-carboxylate (thiencarbazone-methyl); 2-[(4,6-dimethoxypyrimidin-2-yl)carbamoylsulfamoyl]-4-formamido-N,N-dimethylbenzamide (foramsulfuron); methyl 3-chloro-5-[(4,6-dimethoxypyrimidin-2-yl)carbamoylsulfamoyl]-1-methylpyrazole-4-carboxylate (halosulfuron-methyl); sodium (5-iodo-2-methoxycarbonylphenyl)sulfonyl-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)carbamoyl]azanide (iodosulfuron-methyl-sodium); and 3,6-dichloro-2-methoxybenzoic acid (dicamba).

Khakiweed (Alternanthera pungens Kunth) Growth Response to Mowing Height and Frequency

The effect of mowing regimens on lateral spread of khakiweed (Alternanthera pungens Kunth) was determined through field studies conducted over a 3-month period in Texas during 2009 and 2010. Treatments were selected to simulate mowing regimens common to intensively managed common bermudagrass [Cynodon dactylon (L.) Pers.] turf and included heights of 1.3 cm (three times/wk), 2.5 cm (two times/week), and 5.1 cm (two times/week). A non-mowed control was included for comparison. Differences in lateral spread of khakiweed among mowing regimens were apparent 4 weeks after initial treatment (WAIT). However, plant diameter increased for all mowing regimens over the course of the trial. Khakiweed plants subjected to the 1.3-cm mowing regimen did not increase in diameter from Week 2 through Week 12, whereas the other two mowing regimens exhibited steady increases in plant diameter over the same time period. By 12 WAIT, non-mowed control plots measured 80.8 cm in diameter, whereas those maintained at 1.3 cm measured 55.3 cm. Comparatively, plants subjected to the 2.5- and 5.1-cm mowing regimens measured 64.7 and 68.8 cm, respectively. Therefore, khakiweed infestations may be more prevalent in bermudagrass mowing heights commonly used for golf course roughs, athletic fields, and home lawns (2.5 cm or greater). However, the production of a thick taproot high in carbohydrate content may enable khakiweed to regenerate from frequent defoliation common to fairway mowing regimes (2.5 cm or less). Adjustments in mowing height may not be enough to effectively reduce khakiweed populations in bermudagrass turf.

Sequential Postemergence Applications for the Control of Khakiweed in Bermudagrass Turf

Khakiweed (Alternanthera pungens Kunth) response to single and sequential herbicide applications was evaluated during the summer of 2009 and 2010 in Texas. No bermudagrass phytotoxicity was observed throughout the length of each trial regardless of herbicide treatment. Carfentrazone at 0.034 kg a.i./ha, metsulfuron + carfentrazone at 0.021 + 0.034 kg a.i./ha, and trifloxysulfuron + carfentrazone at 0.018 + 0.034 kg a.i./ha exhibited 74% to 85% khakiweed control 2 weeks after initial treatment (WAIT) regardless of application regime. Control with carfentrazone (0.017 kg a.i./ha) was only 63% to 65% 2 WAIT regardless of application regime. Metsulfuron and trifloxysulfuron treatments exhibited 54% or less khakiweed control 2 WAIT regardless of rate. Six weeks later (8 WAIT), sequential applications of metsulfuron exhibited 98% control regardless of rate, whereas control with single applications was 79% to 87%. Sequential applications of trifloxysulfuron exhibited 86% to 88% khakiweed control 8 WAIT regardless of rate, whereas single applications exhibited 47% or less control. Carfentrazone treatments exhibited 5% or less control regardless of rate or sequential application 8 WAIT. Tank-mixing metsulfuron or trifloxysulfuron with carfentrazone did not improve control 8 WAIT compared with either sulfonylurea herbicide applied alone. Although initial khakiweed injury was observed in all treatments, effective long-term control was difficult to achieve. Excellent control (95% to 97%) was exhibited by sequential metsulfuron applications 12 WAIT regardless of rate. Sequential applications of trifloxysulfuron (0.018 or 0.028 kg a.i./ha) and single applications of metsulfuron at 0.042 kg a.i./ha exhibited moderate khakiweed control (75% to 80%) 12 WAIT. All other treatments exhibited 57% or less khakiweed control 12 WAIT. Efficacy of sequential metsulfuron applications is a strong incentive for its adoption over trifloxysulfuron applications for the control of khakiweed in bermudagrass turf.

Response of Kentucky Bluegrass (Poa pratensis L.) Cultivars and Selections to Bispyribac-sodium Herbicide

Annual bluegrass (Poa annua L.) is a problematic weed in Kentucky bluegrass (Poa pratensis L.). Bispyribac-sodium herbicide can effectively control established annual bluegrass in other cool-season turfgrasses, but unacceptable injury to Kentucky bluegrass has been reported. However, only a few Kentucky bluegrass cultivars have been evaluated. The objective of this study was to determine the extent of intraspecific variability among Kentucky bluegrass cultivars and selections to sequential applications of bispyribac-sodium herbicide. Field experiments were conducted in 2004 and 2005 in New Jersey to determine the response of 55 Kentucky bluegrass cultivars and selections to bispyribac-sodium. The herbicide was applied at 188 g·ha−1 followed 3 weeks later by a second application of 281 g·ha−1. Kentucky bluegrass injury ranged from 8% to 93% 8 weeks after initial treatment (WAIT). ‘Blackstone’, ‘Serene’, and A98-962 were the most tolerant to bispyribac-sodium, exhibiting less than 20% injury 8 WAIT. Conversely, ‘Washington’, 95AN-10, and ‘Avalanche’ were the most susceptible with up to 93% injury 8 WAIT. The range in tolerance to bispyribac-sodium within Kentucky bluegrass indicates the potential for the identification and development of cultivars with improved tolerance to bispyribac-sodium herbicide.

Growth Control of ‘Taylortown Red’ and ‘Homestead Purple’ Verbena with Pistill in Nursery Production

Abstract Verbena canadensis ‘Homestead Purple’ and ‘Taylortown Red’ were treated with one or two spray applications of the plant growth regulator (PGR) Pistill (ethephon) at 0, 250, 500, 750, or 1000 ppm. Plants were in 3.8 liter (1 gal) containers under outdoor nursery conditions. Plant widths of ‘Homestead Purple’ verbena were suppressed linearly with increasing Pistill concentrations up to 24% at 2 weeks after initial treatment (WAT) and up to 18% at 4 WAT. Widths of ‘Taylortown Red’ verbena were suppressed 22% at 2 WAT with a single application at 500 to 1000 ppm, and linearly up to 33% at 4 WAT with 2 applications. Two applications of Pistill suppressed heights and widths of both cultivars at 7 WAT compared to one application.

Evaluating Bispyribac-sodium and Sulfosulfuron for Control of Roughstalk Bluegrass

Roughstalk bluegrass (Poa trivialis L.) is a troublesome weed on golf courses, home lawns, and athletic fields from the Midwest to the mid-Atlantic states. Bispyribac-sodium and sulfosulfuron have recently been labeled for roughstalk bluegrass control, but their use needs to be refined. Our objective was to determine the most effective herbicide strategies for control of roughstalk bluegrass. Initial studies were conducted during 2005 in Illinois and Indiana and follow-up studies in 2006 in Indiana, Illinois, South Dakota (partial shade and full sun), and Wisconsin. Applications starting in the warmer temperatures of late May and June 2005 were more effective than those starting in mid-May. Bispyribac-sodium (a.i.) was applied at 74 or 114 g·ha−1 four times at 2-week intervals decreased roughstalk bluegrass cover to 1% and 0% 12 weeks after initial treatment (WAIT) in Illinois and Indiana in 2005, respectively, whereas sulfosulfuron (a.i.) at 13 or 27 g·ha−1 applied twice at 2-week intervals decreased cover to no less than 18%. In 2006, bispyribac-sodium was most effective in Indiana and Illinois decreasing cover to as low as 4%, whereas sulfosulfuron was most effective in South Dakota resulting in a decrease in cover to as low as 7%, and both herbicides performed similarly in Wisconsin. Three applications of sulfosulfuron (a.i.) at 27 g·ha−1 at 2-week intervals or four applications of bispyribac-sodium (a.i.) at 56 or 74 g·ha−1 at 2-week intervals were most effective for roughstalk bluegrass control.

Benzyladenine (BA) Promotes Ramet Formation in Hemerocallis

Abstract In 2000 and 2004, cultivars of Hemerocallis were treated with foliar applications of 2500 or 5000 ppm benzyladenine (BA) for 1, 2, 3, 4 or 5 consecutive weeks. In both years, BA increased ramet production of all cultivars although treatment response was cultivar dependent. In 2000, an increasing number of BA applications resulted in ‘Lavinia Love’ and ‘Beguine’ forming 1.6 to 3.2 and 0.7 to 1.1 more ramets, respectively, than control plants at 9 weeks after initial treatment (WAT), regardless of concentration. Increasing BA concentration increased ramet formation by up to one ramet in ‘Beguine’ and up to 3 ramets in ‘Lavinia Love’ at 9 WAT, regardless of the number of applications. At 9 WAT in 2004, increasing weekly applications of BA increased ramet formation in ‘Dainty Deb’ from a mean of 1.3 ramets with one application to a mean of 3.0 ramets with five applications, and in ‘Sarah Sikes hybrid’ from 0.5 ramets with one application to 2.1 ramets with five applications, regardless of concentration. Compared to control plants, ‘Dainty Deb’ increased ramet production by 1.9 ramets and 2.3 ramets at 9 WAT in 2004 when treated with 2500 ppm and 5000 ppm BA, respectively, regardless of the number of applications. Compared to untreated controls, ‘Sarah Sikes hybrid’ formed 1.1 and 1.3 more ramets when treated with 2500 ppm and 5000 ppm BA, respectively.

BA Application Frequency and Concentration Effects on Two Indian Hawthorn Cultivars

Abstract Benzyladenine (BA) is a synthetic cytokinin that promotes lateral shoot development in herbaceous and woody ornamentals and may be a viable alternative to mechanical pruning in nursery production. A study was conducted to determine the effects of BA application number, interval and concentration on two Indian hawthorn [Rhaphiolepis Lindl. Cor. Poir. indica (L.) Lindl. (Crataegus indica L.)] cultivars. In spring 2002, actively growing ‘Olivia’ and ‘Eleanor Taber’ received three applications of 2500 or 5000 ppm BA at a one-, two-, or three-week interval. Data collected four weeks after initial treatment (WAT) reflected the effects of one, two, or three BA applications at each concentration. At this time new shoot counts in both cultivars and foliar injury in ‘Olivia’, but not in ‘Eleanor Taber’, increased with increasing number of applications and BA concentration. Data collected 12 WAT reflected the effects of BA application interval and concentration. At this time new shoot counts increased with decreasing application interval in ‘Olivia’, while ‘Eleanor Taber’ formed the most new shoots when BA was applied at a two-week interval. All treated plants sustained minimal to moderate injury to immature foliage. The experiment was repeated in 2003 using 1750 ppm and 3500 ppm BA on ‘Olivia’ Indian hawthorn. Applications were halted at the first sign of foliar injury resulting in plants treated at one, two, and three-week intervals receiving three, two, and two applications, respectively. New shoot counts on ‘Olivia’ treated at the three application intervals were similar, but greater than those on untreated plants. Control plants had a foliar injury rating similar to that of plants treated at a two or three-week interval, but less than that of plants treated at a one-week interval. Growth index was not affected by treatment in either year.

Hybrid Bermudagrass ( Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy) Control with Glyphosate and Fluazifop

During bermudagrass golf course renovations, complete removal of existing bermudagrass is imperative for establishing a pure, contaminant-free stand of a new bermudagrass cultivar. Field studies were conducted at the West Florida Research and Education Center near Jay, FL in 2001 and 2002 to evaluate hybrid bermudagrass control. Glyphosate (4.5 kg ai/ha), glyphosate (4.5 kg ai/ha) + ammonium sulfate (1 kg of N per ha), glyphosate (4.5 kg ai/ha) + fluazifop-p-butyl (0.4 kg ai/ha), and glyphosate (4.5 kg ai/ha) + fluazifop-p-butyl (0.4 kg ai/ha) + ammonium sulfate (1 kg of N per ha) were applied sequentially either two or three times at 4-week intervals. At 12 weeks after initial treatment (WAIT) (4 weeks after final herbicide application), glyphosate + fluazifop-p-butyl and glyphosate + fluazifop-p-butyl + ammonium sulfate applied three times provided 99% bermudagrass control. Single-degree-of-freedom contrast analysis indicated that there was a 12% increase in control for three versus two applications at 12 WAIT (P < 0.01). Contrast analysis also indicated a 7% (P < 0.01) increase in bermudagrass control 12 WAIT with fluazifop-p-butyl + glyphosate relative to glyphosate alone. The addition of ammonium sulfate increased control at 4 WAIT (P < 0.05) by 4%, however, no differences in control were observed at 8 and 12 WAIT. Turfgrass managers considering bermudagrass renovation should use three applications of glyphosate + fluazifop-p-butyl at 4.5 + 0.4 kg ai/ha with repeat applications scheduled 4 weeks apart to obtain complete control of the existing bermudagrass.