Japanese stiltgrass is regarded as one of the most troublesome invasive species in the United States. It is commonly found invading forested areas; however, more recently it has been noted to be invading golf course roughs and out-of-play areas. The purpose of this study was to evaluate POST herbicide control of Japanese stiltgrass in golf course and highly maintained turfgrass facilities. None of the treatments provided >80% Japanese stiltgrass control 2 wk after treatment (WAT). At 4 WAT >80% Japanese stiltgrass control was observed with MSMA, MSMA + metribuzin, amicarbazone, and sethoxydim, whereas metsulfuron, pinoxaden, and imazapic provided minimum control. By 8 WAT, MSMA, MSMA + metribuzin, amicarbazone, and sethoxydim provided >98% control, whereas quinclorac, metsulfuron, pinoxaden, and imazapic provided no visible control. Thiencarbazone-methyl + foramsulfuron + halosulfuron-methyl, and sulfentrazone provided limited (≤60%) control. This study indicates that POST control of Japanese stiltgrass can be achieved with MSMA, MSMA + metribuzin, amicarbazone, and sethoxydim. Future research should include long-term control over multiple growing seasons, repeat applications of herbicides, and evaluation of herbicides in combination for increased and longer-term Japanese stiltgrass control.

Two species, torpedograss and Southern watergrass, are very difficult to selectively control when they invade desirable turfgrass stands. The purpose of this study was to evaluate selective control of torpedograss and Southern watergrass in ‘Tifway’ bermudagrass turf. Greater than 86% control of torpedograss was observed 4 wk after sequential treatment (WAST) with quinclorac, trifloxysulfuron-sodium, quinclorac and trifloxysulfuron-sodium, sulfentrazone + imazethapyr and quinclorac and trifloxysulfuron-sodium, and quinclorac and trifloxysulfuron-sodium followed by (fb) glyphosate. However, by 8 WAST, control was reduced to <36% for all treatments. Greatest Southern watergrass control was achieved 4 WAST with trifloxysulfuron-sodium (83%), and thiencarbazone-methyl + foramsulfuron + halosulfuron-methyl (75%). Limited control (<30%) was observed with other treatments. By 8 WAST, Southern watergrass control was <12% for all treatments. This study suggests that short-term control/suppression of these two species is possible; however, long-term control is limited with single-year programs. These weeds will probably require multiple applications in successive years to reduce infestations. Future research should continue to screen other herbicides, combinations, and timings for control of these and other perennial grass weeds.

Susceptibility of a system to colonization by a weed is in part a function of environmental resource availability. Doveweed [Murdannia nudiflora (L.) Brenan] can establish in a variety of environments; however, it is found mostly in wet or low-lying areas with reduced interspecies competition. Four studies evaluated the effect of mowing height, interspecies competition, and nitrogen, light, and soil moisture availability on M. nudiflora establishment and growth. A field study evaluated the effect of mowing height on M. nudiflora establishment. In comparison with unmowed plots, mowing at 2 and 4 cm reduced spread 46% and 30%, respectively, at 9 wk after planting. Effect of mowing height and nitrogen fertilization on ‘Tifway’ bermudagrass (Cynodon dactylon Burtt-Davy×C. transvaalensis L. Pers.) and M. nudiflora interspecies competition was evaluated in a greenhouse trial. Murdannia nudiflora coverage was 62% greater in flats maintained at 2.6 cm than flats maintained at 1.3 cm. Supplemental application of 49 kg N ha−1 mo−1 increased M. nudiflora coverage 75% in comparison with 24.5 kg N ha−1 mo−1. A difference in M. nudiflora coverage could not be detected between flats receiving 0 and 24.5 kg N ha−1 mo−1, suggesting moderate nitrogen fertilization does not encourage M. nudiflora colonization. Effect of light availability on M. nudiflora growth and development was evaluated in a greenhouse study. Growth in a 30%, 50%, or 70% reduced light environment (RLE) did not affect shoot growth on a dry weight basis in comparison with plants grown under full irradiance; however, internode length was 28% longer in a 30% RLE and 39% longer in a 50% and 70% RLE. Effect of soil moisture on M. nudiflora growth and development was evaluated in a greenhouse study. Plants maintained at 50%, 75%, and 100% field capacity (FC) increased biomass>200% compared with plants maintained at 12.5% or 25% FC.

Goosegrass is a weedy C4 species throughout the world and a major pest in turfgrass systems. Further research is needed to characterize morphological events of goosegrass germinating in late summer to enhance long-term management programs. The objective of this study was to determine whether goosegrass germinating on August 15 will complete a life cycle before the first killing frost, typically November 15 in Clemson, SC. A biotype from Clemson, SC, was collected and a growth-chamber experiment was conducted to simulate autumn maximum and minimum temperatures. Culm, leaf, root, and raceme biomass measurements were recorded weekly, and growth curves were modeled. The inflection point (i.e., point of maximum growth) occurred for the following growth parameters: culm dry weight at 26.5 d after emergence (DAE), leaf dry weight at 26.6 DAE, number of racemes per plant at 50.7 DAE, raceme dry weight (including germinable seed) at 56.0 DAE, and root dry weight at 42.1 DAE. The completion of the life cycle occurred on October 22 (68 DAE), approximately 3 wk before the typical first killing frost in Clemson, SC. In summary, turf managers need to address goosegrass that germinates through approximately the first week of September at this location to avoid production of viable seed.

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.

A 3-yr study investigated highbush blackberry control in bahiagrass turf using selective herbicides. Triclopyr applied alone at ≤ 0.56 kg/ha and in combination with other herbicides provided best (75 to 95%) control for up to 52 wk after treatment with minimal damage to bahiagrass turf. Triclopyr formulations (3A vs 4EC) provided similar highbush blackberry control and bahiagrass tolerance. The addition of either 2,4-D, dicamba, hexazinone, or sulfometuron to triclopyr provided slightly better blackberry control, but increased bahiagrass turf damage. Fluroxypyr applied at 0.14 to 0.28 kg/ha provided 60 to 80% control of highbush blackberry 12 WAT. Glyphosate and glufosinate treatments provided unacceptable highbush blackberry control and/or unacceptable bahiagrass turf injury. The addition of oxadiazon for residual control of subsequent highbush blackberry emergence was ineffective.

Field trials evaluated sequential applications of plant growth retardants (PGRs) to bahiagrass for a 3-yr period at two Florida locations: Newberry (north Florida) and Okeechobee (south Florida). Seven PGRs from various chemical families were used: glyphosate, fluazifop, sethoxydim, maleic hydrazide, trinexapac-ethyl, imazapic, and imazaquin. In 1991 and 1992, PGRs reduced turf color for 2 to 4 wk after treatment (WAT) at the Newberry location but remained above acceptable levels (> 5.0) and recovered by 6 WAT. In 1993, glyphosate, fluazifop, and maleic hydrazide reduced turf color below acceptable levels (< 5.0) 4 WAT, but turf color was acceptable by 6 WAT. Turf color was slightly reduced following single and sequential imazapic applications in Okeechobee; however, turf recovered by 8 WAT. Cumulative seedhead suppression at both locations increased during the 3 yr resulting in at least a 60% reduction in seedhead numbers. Seedhead production each year was 10 to 50% less at 12 WAT in treated plots than in the previous year. Single applications of imazapic and imazapic + imazaquin provided 85 to 100% seedhead suppression for 12 WAT and 100% suppression for up to 16 wk following sequential applications made 8 wk after the initial application (WAI). Single applications of glyphosate, fluazifop, and maleic hydrazide provided ≥ 70% seedhead suppression for 4 to 8 WAT. Sequential applications of fluazifop made 8 WAI provided > 70% control of seedheads through 8 to 16 WAI for 3 yr.

Torpedograss has invaded fine turfgrasses in the Southern U.S. due to its tolerance to most commonly used turfgrass herbicides. Research was conducted to determine torpedograss and ‘Tifway’ bermudagrass tolerance to quinclorac and tank-mix combinations with other turf herbicides. Quinclorac rates in excess of 2.2 kg ai/ha were required for control (≥ 80%) of torpedograss. Sequential applications were more effective than single applications. Generally, sequential applications made 3 wk after the initial were more effective than delaying sequential applications until 4 wk after the initial application. Tifway bermudagrass injury from quinclorac applied at 4.5 kg/ha, or at 2.2 kg/ha followed by a sequential application of 1.1 or 2.2 kg/ha, was observed at 4 to 10 wk; however, turf recovered thereafter. Sequential applications of quinclorac plus imazaquin (1.1 + 0.6 kg/ha) increased torpedograss control (approximate 35%) as compared to quinclorac plus MSMA (1.1 + 1.1 kg/ha) but also decreased turf quality versus quinclorac applied alone or in combination with MSMA. Quinclorac applied at 2.2 kg/ha followed by 1.1 kg/ha applied 3 or 6 wk after the initial controlled torpedograss best with least reduction in bermudagrass quality. Quinclorac is the first herbicide reported to selectively control torpedograss in bermudagrass turf.

In field experiments conducted near Marianna, Trenton, and Archer, FL in 1990 and 1991, nicosulfuron applied 55 weeks after planting (WAP) at 18, 27, 36, or 54 g ai/ha injured peanut initially. When applied 7 WAP, only the two higher nicosulfuron rates injured peanut more than 10%. By 6 wk after application, crop injury was less than 8% for all treatments, except the highest (54 g/ha) rate. Nicosulfuron applied 5 or 7 WAP at 54 g/ha reduced peanut yield and sound mature kernels.

Field experiments conducted in Marianna, Trenton, and Archer, FL in 1990 and 1991 investigated the effect of time of application of nicosulfuron and nicosulfuron mixtures on ‘Sunrunner’ peanut. Nicosulfuron was applied alone at 36 g ai/ha and in mixture with acifluorfen, bentazon, chlorimuron, chlorothalonil, fluazifop-P, imazethapyr, lactofen, or pyridate at 5, 7, or 9 weeks after planting (WAP). Applying nicosulfuron with chlorimuron, pyridate, or imazethapyr increased visible peanut injury and reduced yields more than nicosulfuron alone. Conversely, nicosulfuron applied with acifluorfen or lactofen was less injurious than nicosulfuron applied alone. Bentazon, chlorothalonil, and fluazifop-P generally did not influence phytotoxicity from nicosulfuron. Peanut tolerance to nicosulfuron increased with age.

Field experiments were conducted near Marianna, Trenton, and Archer, FL in 1990 and 1991 to investigate the effect of nicosulfuron mixtures and time of application on five peanut cultivars. Nicosulfuron at 54 g ai/ha was applied alone or in mixture with 2,4-DB at 280 g ai/ha 5 weeks after planting (WAP), 9 WAP, or 5 plus 9 WAP. Injury was greater from early and sequential nicosulfuron applications while a single application 9 WAP typically did not cause significant injury or reduce peanut yield. The 5 WAP and 5 plus 9 WAP applications often caused early visible injury and sometimes reduced peanut yield. When peanut yields were compared, ‘Florigiant’ was the most sensitive cultivar while ‘Southern Runner’ and ‘Valencia’ were more tolerant to nicosulfuron. ‘Sunrunner’ and ‘NC-7’ were intermediate in tolerance to nicosulfuron. In several instances, the addition of 2,4-DB to nicosulfuron reduced initial crop injury and ameliorated yield losses resulting from nicosulfuron applied alone.

Kyllinga species are becoming more prevalent in turfgrass sites throughout North America. The effects of nitrate (50, 200, and 400 mg L−1), temperature (33/24, 25/17, 19/11 C day/night, respectively), and light on seed germination of three Kyllinga species were investigated in growth chambers. Nitrate concentrations did not stimulate Kyllinga species seed germination compared with untreated seeds. All Kyllinga species seeds failed to germinate in darkness but resumed germination once they were placed in light. This is an important pest management strategy because a dense, uniform turfgrass stand with its minimum light penetration to the soil would minimize Kyllinga species seed germination. Higher temperatures increased seed germination rate and percentage of each species after 8 wk. Maximal (> 90%) K. brevifolia germination occurred 2 to 4 wk after initiation in every seed study, whereas K. squamulata seeds germinated continuously. Minimal (< 10%) K. pumila seeds germinated until alternating diurnal temperatures were imposed.

This research examined the effect of duration of the warm cycle and number of fluctuating temperature/light cycles on goosegrass seed germination. Less than 10% goosegrass seed germination occurred at constant temperatures of 20, 25, and 35 C, while 99% germinated at daily fluctuating temperature regimes of 20 C for 16 h and 35 C for 8 h with light. Increasing the number of fluctuating temperature cycles increased goosegrass seed germination. Fluctuating temperature cycles with 22 h at 20 C and 2 h at 35 C with light strongly stimulated germination, but not as much as the cycle with 8 h at 35 C. Goosegrass seed germination ceased once the fluctuating temperature regime was discontinued, and constant 20 C with 8 h light daily was reimposed. Germination occurred only on resumption of fluctuating temperature cycles. Seed incubated for several weeks in a moist environment at constant 20 C had 81 to 91% germination with two cycles of 20 C for 16 h and 35 C for 8 h, compared to 14% for fresh seeds.

Postemergence grass weed control in turf-type bermudagrass is currently available only with repeated applications of organic arsenicals and/or with combinations of metribuzin which decrease turf quality. Research was conducted to determine tolerance of the turf-type bermudagrass cultivars, Tifway, Ormond, and common, to diclofop rates ranging from 0.54 to 4.48 kg ai ha-1 with and without MSMA (2.2 kg ai ha-1) and metribuzin (0.2 kg ai ha-1). Bermudagrass cultivars tolerated diclofop well. When injury was evident, a rate response was noted, with higher rates (3.4 and 4.5 kg ha-1) resulting in increased phytotoxicity. However, this level of phytotoxicity was acceptable and the turf soon recovered (3 to 14 d). The addition of crop oil concentrate (1.25% v/v) did not affect turf quality. Addition of MSMA resulted in slightly lower turf quality than diclofop alone. However, these responses were acceptable and usually the turf recovered by 14 d after treatment. Metribuzin applied alone or in combination with diclofop damaged turf to unacceptable levels and up to 21 d were required for turf recovery.

The sedge genus Kyllinga consists of 40 to 45 species distributed in tropical, subtropical, and warm temperate regions around the world (KUkenthal 1936; Tucker 1987). This genus of low rhizomatous perennials or cespitose annuals is classified in the large cosmopolitan family Cyperaceae. Many Kyllinga species are considered weedy (Holm et al. 1979; Tucker 1987), while Kyllinga nervosa Steudel is considered an important forage plant in Africa (McNaughton 1985).

Field and greenhouse studies were conducted to evaluate selected PRE-applied herbicides for sprangletop control. In greenhouse studies, oxadiazon and dithiopyr provided excellent (> 89%) red sprangletop (L. filiformis) control. Pendimethalin and metolachlor + atrazine provided good (80–89%) to excellent control for 6 mo and 2 mo during studies 1 and 2, respectively. Isoxaben and atrazine provided poor (< 70%) control during both greenhouse studies. In field studies, good to excellent bearded sprangletop (L. fascicularis) control followed dithiopyr, pendimethalin, metolachlor, and metolachlor + atrazine treatments. Dithiopyr at 0.8 kg ai/ha provided best (> 95%) sprangletop control throughout the 6-mo testing period. Under field conditions, control was inconsistent following oxadiazon with good to excellent control during one study and poor control in another study. Better or equal control than metolachlor + atrazine followed dithiopyr, pendimethalin, and metolachlor alone treatments. Oxadiazon also provided similar or better control than metolachlor+atrazine in three of four studies. Over all studies, dithiopyr provided best sprangletop control, followed by metolachlor, metolachlor + atrazine, pendimethalin, and oxadiazon. Isoxaben and atrazine treatments provided poorest or inconsistent sprangletop control.

Greenhouse and field experiments were performed to investigate diclofop rate and mowing height interactions on goosegrass control and ‘Tifgreen’ and ‘Tifdwarf’ bermudagrass tolerance. In greenhouse experiments, greatest goosegrass control was achieved with diclofop when plants were maintained at 1.3 cm. Increased diclofop rates were required to suppress goosegrass mowed higher than 1.3 cm or unmowed. Greater than 90% goosegrass control was achieved with the combination of 1.3-cm mowing height and 0.6 kg ai ha–1 of diclofop. In field experiments, a minimum of 2 weeks was necessary for complete herbicidal activity. Diclofop at 1.1 kg ha–1 provided >90% control of goosegrass mowed between 1.9 to 2.5 cm. The addition of nonionic surfactant (0.25% by vol) to diclofop did not influence control. The addition of metribuzin (0.1 kg ai ha–1) to diclofop resulted in initial increased control, but it was transient The addition of MSMA (2.2 kg ai ha–1) to diclofop reduced goosegrass control an average of 18% compared to diclofop treatments alone. Tifdwarf bermudagrass was more sensitive to diclofop compared to Tifgreen. Seven to 14 days were required for Tifdwarf to recover from initial injury. This injury, although significant, was acceptable for bermudagrass used for golf greens. Clipping weights following treatment were also less for Tifdwarf than Tifgreen.

Carpetgrass is a warm season grass used in the south as low maintenance turf, especially in wet areas where other turf species do not persist. The response of carpetgrass to postemergence (POST) herbicides currently available for turf producers has not been thoroughly investigated and was the objective of four experiments conducted over a 2-yr period. Slight reduction in turf quality followed application of atrazine (2.2 kg ai ha-1), bentazon (2.2 kg ai ha-1), imazaquin (0.4 and 0.6 kg ai ha-1), mecoprop (1.1 kg ai ha-1), triclopyr (0.6 kg ai ha-1), metsulfuron (0.2 kg ai ha-1), 2,4-D (1.1 kg ai ha-1), 2,4-D plus dicamba (0.8 + 0.3 kg ai ha-1), and 2,4-D plus dicamba plus mecoprop (0.9 + 0.1 + 0.5 kg ai ha-1). Marginally acceptable turf quality followed sulfometuron (0.2 kg ai ha-1), sethoxydim (0.3 and 0.6 kg ai ha-1), and diclofop (2.2 kg ai ha-1) treatments. Unacceptable turf quality resulted from asulam (2.2 kg ai ha-1) and MSMA (1.1 and 2.2 kg ai ha-1) treatments. Carpetgrass tolerated most POST broadleaf and sedge herbicides but was sensitive to most POST grass herbicides used in other turf species, with the exception of sethoxydim.

Kyllinga species are becoming more common throughout the southeastern United States. Two species, Kyllinga brevifolia and Kyllinga squamulata, in particular are prevalent weeds in turfgrass. To better understand these weeds, growth chamber studies determined the growth of K. brevifolia, K. squamulata, and Cynodon dactylon × Cynodon transvaalensis as influenced by three temperature regimes (33/24, 25/17, 19/11 C day/night, respectively). Temperature influenced almost all aspects of Kyllinga species growth. Plant height of both Kyllinga species increased nearly twofold after 8 wk at high temperatures. Plants were mowed each week to 2.5 cm; both species produced more than twice as many clippings by 8 wk at high (33/24 C) temperatures than at low (19/11 C) temperatures. Destructive analysis at 8 wk revealed that K. brevifolia shoot and root weight increased with decreasing temperature, whereas K. squamulata shoot and root weights were not affected by temperature. Shoot weight percentage for both Kyllinga species increased from 59% in medium temperatures to 69% in high temperatures. K. brevifolia shoot weight percentage decreased to 53% in low temperatures, whereas K. squamulata shoot weight percentage increased to 72%. K. brevifolia inflorescences formed at 2, 3, and 5 wk in high, medium, and low temperatures, respectively, whereas K. squamulata flowered immediately in all temperatures. C. dactylon × C. transvaalensis and Kyllinga species growth were similar within each temperature regime throughout the 8-wk study.

Studies were conducted for 12 wk from June 16 to September 8, 2003 and July 10 to October 4, 2004 with the objective of evaluating growth regulation, lateral regrowth, and injury of Tifway bermudagrass [Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy Tifway] in response to two GA-inhibiting plant growth regulators, trinexapac-ethyl and flurprimidol. Trinexapac-ethyl was applied alone at 0, 0.052, and 0.104 kg ai/ha and flurprimidol alone at 0, 0.14, and 0.28 kg ai/ ha, plus all combinations. Applications were made every 3 wk for the duration of the study. Tifway bermudagrass clipping yield was reduced 33% and 54% by trinexapac-ethyl at 0.104 kg/ha at 4 and 8 wk after initial treatment (WAIT), respectively. Flurprimidol at 0.28 kg/ha reduced clipping yield 49% 8 WAIT. Lateral regrowth was reduced 20% 2 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 26% 2 WAIT by flurprimidol at 0.28 kg/ha. Lateral regrowth was reduced 13% 4 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 15% 4 WAIT by flurprimidol at 0.28 kg/ha. Overall, acceptable injury (<30%) was observed with a trinexapac-ethyl and flurprimidol tank mixture; however, this evaluation did not indicate an advantage in growth regulation when using a tank mixture of these products, compared to using them alone.