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Tahitian bridal veil [Gibasis pellucida (M. Martens & Galeotti) D.R. Hunt], a Central and South America native plant that is often confused with another more well-known invasive plant, small leaf spiderwort (Tradescantia fluminensis Vell.), has become invasive in natural areas throughout Florida. However, very little is known regarding herbicide control or other methods. To begin the process of developing herbicide recommendations for land managers who are working to control G. pellucida, multiple postemergence herbicides were screened for efficacy in a shaded greenhouse to determine active ingredients and/or combinations that warrant further investigation under field conditions. Nine different herbicides or combinations, including glyphosate, triclopyr acid, 2,4-D + triclopyr, aminopyralid, 2,4-D, triclopyr amine, metsulfuron-methyl, fluroxypyr, and glufosinate, were applied at standard label rates and compared with a nontreated control group. Visual control ratings were taken at 2, 4, and 8 wk after treatment (WAT), and shoot dry weights were determined at trial conclusion (8 WAT). Data showed glufosinate and triclopyr (acid and amine) provided the highest level of control, as evidenced by control ratings (100% or complete control) and shoot fresh weight reduction, followed by 2,4-D + triclopyr (∼70%) and fluroxypyr (∼50% control). Metsulfuron-methyl and 2,4-D provided the lowest level of control, with results similar to those for nontreated plants on most evaluation dates.

Ornamental groundcovers are a popular alternative to turfgrass in landscapes due to their low maintenance requirements, pest resistance, and shade tolerance. Weed control is a challenge in these groundcovers because few herbicide options are available. The objective of this research was to determine the tolerance of the groundcovers Asiatic jasmine [Trachelospermum asiaticum (Nakai) ‘Minima'], perennial peanut [Arachis pintoi (Krapov.& W.C. Greg.) ‘Golden Glory'] and dwarf mondo grass [Ophiopogon japonicus (L.f.) Ker Gawl.] ‘Nana'] to herbicides, including bentazon, clopyralid, fluazifop-P-butyl, glufosinate, halosulfuron, imazaquin, sethoxydim, sulfentrazone, and sulfosulfuron applied at approximately 2 times the label rate. Asiatic jasmine and perennial peanut were evaluated in Apopka, FL and dwarf mondo grass was evaluated in Mobile, AL. Bentazon, clopyralid, glufosinate, glyphosate, and sulfosulfuron caused unacceptable injury and/or a reduction in shoot growth for all three species while fluazifop-P-butyl and sethoxydim caused no injury to any species. Halosulfuron caused minor injury but significantly reduced growth of dwarf mondo grass. Sulfentrazone caused no injury to Asiatic jasmine or perennial peanut but caused severe injury to dwarf mondo grass after only one application. Similarly, imazaquin caused only minor injury to Asiatic jasmine and dwarf mondo grass but significantly reduced growth of perennial peanut after two applications.Index words: Postemergence herbicides, groundcovers, mondo grass, perennial peanut, Asiatic jasmine.Chemicals used in this study: Bentazon (Basagran® T/O), 3-(1-methylethyl)-1H-2, 1,3-benzothiadiazin-4(3H)-one 2,2-dioxide, clopyralid (Lontrel), 3,6-dichloro-2pyridinecarboxylic acid, fluazifop-P-butyl (Fusilade® II), (2R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid, Glufosinate (Finale®), 2-amino-4-(hydroxymethylphosphinyl)butanoic acid, Glyphosate (Ranger® PRO), N-phosphonomethyl)glycine, Halosulfuron-methyl (SedgeHammer®), methyl 3-chloro-5-[[[[4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]-1-methyl-1H-pyrazole-4-carboxylate, Imazaquin (Sceptor® T&O), 2-[4,5-dihydro-4-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid, Sethoxydim (Sethoxydim SPC), 2-[1-ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one, Sulfentrazone (Dismiss®), N-[2,4-dichloro-5-[4-difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]phenyl]methanesulfonamide, Sulfosulfuron (Certainty®), 1-(4,6-dimethoxypyrimidin-2-yl)-3-[(2-ethanesulfonyl-imidazo[1,2-a]pyridine-3-yl]sulfonylurea.Species used in this study: Asiatic jasmine ‘Minima' (Trachelospermum asiaticum ‘Minima'), perennial peanut (Arachis pintoi ‘Golden Glory'), dwarf mondo grass (Ophiopogon japonicus ‘Nana').

Praxelis is an annual to short-lived perennial herb in the Asteraceae family and an emerging problematic weed species in Florida nurseries. The objective of these experiments was to determine efficacy of selected PRE and POST herbicides for control of praxelis. An additional experiment was conducted to determine efficacy of the same PRE herbicides for control of bluemink, a weed similar in appearance to praxelis that is also common in Florida. The granular herbicides dimethenamid + pendimethalin, flumioxazin, oxyfluorfen + pendimethalin, oxyfluorfen + prodiamine, and trifluralin + isoxaben were evaluated, along with spray-applied formulations of dimethenamid, indaziflam, and prodiamine + isoxaben. Flumioxazin consistently provided over 90% control of praxelis at both sites. Indaziflam control was inconsistent between the two sites, providing 100% control in Apopka but only a 22% reduction in weed counts in Balm. Oxyfluorfen + pendimethalin, oxyfluorfen + prodiamine, and prodiamine + isoxaben also provided control (57% to 97% reduction in shoot weight), albeit generally to a lesser degree than was observed with flumioxazin. All PRE herbicides provided similar control of both praxelis and bluemink, with the exception of dimethenamid and dimethenamid + pendimethalin, which reduced bluemink shoot weight more than praxelis. Clopyralid, glyphosate, and triclopyr all provided effective POST control of mature and flowering praxelis through 12 wk after treatment (WAT) and resulted in greater praxelis control than glufosinate. Results suggest that many commonly used PRE and POST herbicides would provide control of praxelis, but use of PRE and POST herbicides as well as sequential applications may be needed for long-term management.

Butterfly pea (Clitoria ternatea) is a unique perennial and leguminous plant that produces brightly colored flowers that can be used as a pH-dependent natural food colorant in culinary and cosmetic preparations. Butterfly pea is commonly propagated from seed. Because of the increased interest in its commercial applications, effective production techniques are necessary to ensure consistent and successful commercial production. The objective of this research was to determine the influence of the substrate type and temperature on butterfly pea germination. Two substrate types (rockwool and commercial soilless substrate mix) and three temperatures (70, 80, and 90 °F) were evaluated to determine their effects on germination of butterfly pea seed. Collected and calculated germination data included germination capacity (G), mean germination time (MT), coefficient of variation of the germination time (cvt), mean germination rate (MR), uncertainty of the germination process (U), and synchrony of the germination process (Z). Differences were observed among substrate temperatures for the MT, cvt, and MR values, with germination greater at both 70 and 80 °F than at 90 °F. Similarly, significant differences among substrate types were observed for the G, MT, cvt, and MR values, with germination of seeds in rockwool outperforming seeds in soilless substrate mix. Because of the high priority for successful and uniform germination in commercial plant production operations, the results suggest that commercial germination of butterfly pea would be best in rockwool at 70 °F. Results of this study can be used for the commercial production of butterfly pea, for which propagation from seed is the primary means of plant production.

Recent interest in the cultivation and use of butterfly pea (Clitoria ternatea) has increased demand for its commercial production. Successful germination of seed is a critical first step to its production; however, few studies have documented factors influential to germination success. To help support commercial production efforts, the influence of substrate temperature and seed scarification technique on germination parameters were evaluated. Two scarification (nicked and nicked and soaked) and three substrate temperature treatments (21, 24, and 27 °C) were imposed on C. ternatea seed. Following treatments, six germination parameters were recorded. Data showed seeds maintained at a substrate temperature of 21 °C reached maximal germination (54.8%) at the longest mean germination time (2.61 d) and slowest mean germination rate (0.39 d-1). Mechanical scarification by nicking the seed coat with a razor blade prior to soaking the seed for 24 hours reached maximal germination (80.95%) at the lowest mean germination time (2.06 d) and fastest mean germination rate (0.51 d-1). Optimal germination was attained when seed was scarified and soaked and then germinated in rockwool substrate maintained at a temperature (To) of 21 °C. Results provide commercial growers with production technique information helpful to fast and efficient germination of C. ternatea seed.

Greenhouse and outdoor container experiments were conducted to determine garden spurge and large crabgrass emergence when seeds were placed either on top of or below three different mulch materials [pine bark (PB), hardwood (HW), or pine straw (PS)] applied at five depths (0, 1.3, 2.5, 5.1, and 10.2 cm). To elucidate mulch characteristics that contributed to weed control, photosynthetic active radiation (PAR) was recorded underneath each mulch layer, moisture retention was monitored for 24 h following irrigation, and particle size was determined using standard soil sieves. HW reduced PAR (97%) more than did PB (90%) or PS (92%) at 1.3 cm, but few or no differences were noted between mulches at greater mulch depths. HW also contained the highest percentage of small particles and consequently retained more water (29%), than PB (14%) or PS (22%) 24 h following a simulated irrigation event. Emergence of large crabgrass and garden spurge was consistently greater when seeds were placed on top of the mulch, compared to seeds placed below. Emergence of both species also tended to respond to increasing depth in a quadratic manner, indicating that once a critical level of mulch was applied (2.5 to 5 cm), further reductions in weed emergence would not be observed, at least over the short term (12 wk). PB and PS tended to provide a greater reduction in emergence of both species compared to HW. This research also indicates that larger particle materials such as PB or PS would be advantageous because of their ability to suppress weed emergence regardless of seed position.

Weed management in container crops is primarily accomplished through frequent PRE herbicide applications and supplemental hand weeding. However, many ornamental species are sensitive to herbicides, and a significant number of tropical plants, ornamental grasses, and foliage crops have not been screened for herbicide tolerance. As nursery crops are produced in inert substrates that are largely composed of bark or peat, strategic fertilizer placement has the potential to significantly reduce weed growth in container-grown ornamentals. Growth and reproduction of three common container nursery weed species, eclipta [Eclipta prostrata(L.) L.], large crabgrass [Digitaria sanguinalis(L.) Scop.], and spotted spurge (Euphorbia maculataL.), were evaluated following fertilization via alternative methods, including subdressing or dibbling in comparison with industry standard practices of topdressing or incorporating a controlled-release fertilizer (17-5-11 [8 to 9 mo.]) to each 3.8-L container at 36.5 g per container. Fertilizer placement had little to no effect on germination ofEclipta prostrataorD. sanguinalis, but incorporation increasedE. maculatagermination by 77% to 183% compared with other placements or a nonfertilized control. Subdressing reduced seed production by 94%, 63%, and 92% forEclipta prostrata,D. sanguinalis, andE. maculata, respectively, compared with the average number of seeds produced in the conventional placement methods (average of incorporation and topdressing). Dibbling fertilizer resulted in similar decreases in the case ofD. sanguinalisandE. maculata, whileEclipta prostrataproduced no seeds when fertilizer was dibbled. Similar to reductions observed in reproduction, subdressing fertilizer resulted in biomass decreases of 90%, 81%, and 85% compared with the average biomass of the incorporation and topdressed placements. Results suggest alternative fertilizer placements could be implemented as part of an integrated weed management program in container production to reduce weed growth.

The objective of these experiments was to determine if preemergence herbicides perform similarly across pine bark that was aged for varying lengths of time including 0, 4, 8, and 12 months after bark removal from harvested trees. Three preemergence herbicides were evaluated for three separate weed species, including 1) Cardamine flexuosa With. (bittercress) with isoxaben, 2) Digitaria sanguinalis (L.) Scop. (large crabgrass) with prodiamine, and 3) Oxalis stricta L. (woodsorrel) with dimethenamid-P. Leaching of herbicides through substrates was evaluated for prodiamine. Weed growth in the various substrates was variable, but few differences were detected in weed growth among the pine bark substrates evaluated. For isoxaben and prodiamine, weed control was similar among the pine bark substrates in most cases when label rates were applied. Although some differences were detected in prodiamine performance across different pine bark ages, a high level of control was achieved in all cases at rates well below manufacturer recommendations. Prodiamine leaching was minimal in all substrates. It would be recommended that growers test substrates for physical properties before use so that irrigation and other production inputs could be modified if needed. In most cases, growers should expect similar performance of preemergence herbicides regardless of pine bark substrate age.

Skunk-vine (Paederia foetidaL.) is an invasive vine native to eastern and southern Asia and is widely distributed in Florida, Hawaii, and other southeastern U.S. states; however, little research has focused on herbicide control. Greenhouse and field experiments were conducted to determine efficacy of aminocyclopyrachlor, aminopyralid, fluroxypyr, glyphosate, imazapic, triclopyr amine, and triclopyr ester at low and high labeled rates when foliar applied toP. foetidaat various growth stages in greenhouse experiments. Longer-term control was evaluated in field experiments in central Florida using the same herbicides. PRE herbicides labeled for use in landscape plantings, including dimethenamid-P, flumioxazin, indaziflam, isoxaben, and prodiamine, were also evaluated in greenhouse trials by seeding containers withP. foetidaseed. In greenhouse experiments, POST herbicides, including aminocyclopyrachlor, aminopyralid, glyphosate, both triclopyr formulations, and the high rate of fluroxypyr (0.24 kg ae ha−1), provided >90% control across all growth stages at 4 mo after treatment with no regrowth observed. Imazapic provided 49% to 89% control, with efficacy decreasing withP. foetidasize, and generally provided less control than other treatments. Field experiments confirmed results from greenhouse studies. In PRE trials, flumioxazin and prodiamine provided better control than all other PRE herbicides evaluated, reducing shoot weights by 99% and 84%, respectively, compared with nontreated controls. Our data suggest all herbicides evaluated POST could potentially be used to manageP. foetida, although less control was achieved with imazapic compared with other herbicides. Further research is needed to determine herbicide efficacy on more mature plants and to develop application methods that would be less injurious to non-target vegetation. In landscapes, flumioxazin or prodiamine could be used for PRE control, but POST options that are labeled for landscape use should be identified in future research.

Mulch is often applied in landscape planting beds for weed control, but little research has focused specifically on mulch and preemergence (PRE) herbicide combinations. The objectives of this research were to determine the efficacy of herbicide + mulch combinations and which factors significantly affected weed control, including herbicide formulation and posttreatment irrigation volumes. Additional objectives were to determine efficacy derived from mulch or herbicides used alone under herbicide + mulch combinations and to identify differences in the additive (herbicide + mulch combinations) or singular (herbicide or mulch) effects compared with the use of herbicides or mulch only. Large crabgrass (Digitaria sanguinalis), garden spurge (Euphorbia hirta), and eclipta (Eclipta prostrata) were used as bioassay species for prodiamine, dimethenamid-P + pendimethalin, and indaziflam efficacy, respectively. The experiment consisted of a factorial treatment arrangement of two herbicide formulations (granular or spray applied), three mulch types [hardwood chips (HWs), pine bark (PB), and pine straw (PS)], two mulch depths (1 and 2 inches), and three levels of one-time, posttreatment irrigation volumes (0.5, 1, and 2 inches). Three sets of controls were used: the first set included three mulch types applied at two depths receiving only 0.5-inch irrigation volume, the second set included only two herbicide formulations and three one-time irrigation volumes, whereas the last set received no treatment (no herbicide or mulch) and only 0.5-inch irrigation volume. High levels of large crabgrass and garden spurge control (88% to 100%) were observed with all herbicide + mulch combinations evaluated at mulch depths of 1 inch or greater. When comparing mulch types, the best eclipta control was achieved with hardwood at 2 inches depth. The spray formulation of indaziflam outperformed the granular formulation in most cases when used alone or in combination with mulch. Overall, the results showed that spray formulations of prodiamine and dimethenamid-P + pendimethalin were more effective than granular formulations when applied alone, whereas indaziflam was more effective as a spray formulation when used both alone and in combination with mulch. Increasing irrigation volume was not a significant factor for any of the herbicide + mulch combinations when evaluating overall weed control.

Tradescantia fluminensis (small-leaf spiderwort; SLSW) is a fast-growing herbaceous groundcover and one of the most problematic invasive plants in Florida. The objective of this research was to determine the efficacy of selected postemergence herbicides for SLSW control in greenhouse and field experiments in Florida. An additional objective was to determine if pre-cutting plants would increase herbicidal efficacy. In greenhouse experiments, cutting mature SLSW plants increased the control of most herbicides evaluated. Overall, triclopyr ester provided the highest level of control along with triclopyr amine, triclopyr choline, and glufosinate, all of which were similar. Few differences were observed between 2,4-D, aminopyralid, metsulfuron-methyl, sulfentrazone, and glyphosate and all provided ≤66% control as evidenced by shoot weight reduction. In field experiments, pre-cutting SLSW had no effect on herbicide efficacy. Triclopyr was again generally the most efficacious treatment, outperforming glyphosate, aminopyralid, glufosinate, and fluroxypyr on most evaluation dates, especially as trials progressed past 5 mo. Overall, data suggest that triclopyr would be the most effective option for SLSW management. However, as efficacy was noted with fluroxypyr, glyphosate, and glufosinate depending upon location, other options exist. Further research is needed to determine reapplication intervals and effects on nontarget native plants in order to develop comprehensive management plans.

Research objectives were to determine the effect of fertilization method (incorporation, subdress, and topdress) on weed growth and the performance of preemergence herbicides applied to soilless substrates. Nursery containers were filled with a pine bark:peat substrate and fertilized at two different rates [4.4 and 9.5 kg.m−3 (8.9 and 19.2 lb.yd−3)] via topdressing, subdressing, or incorporating. Containers were treated with either dimethenamid-P for spotted spurge (Euphorbia maculata L.), flumioxazin for eclipta (Eclipta prostrata L.) or prodiamine for large crabgrass (Digitaria sanguinalis L.). A control was established for each fertilizer rate/placement and weed species that was not treated. Incorporating or subdressing fertilizer resulted in reduced large crabgrass and spotted spurge growth in non-treated containers. Weeds grew larger at the higher fertility rates in both topdress and incorporated treatments but fertilizer rate did not affect growth of spotted spurge or large crabgrass when fertilizers were subdressed. Herbicides generally provided commercially acceptable weed control regardless of fertilizer treatment, but results varied with species. Results suggest that in the absence of herbicides, topdressing may result in greater weed growth compared with subdressing or incorporating fertilizers; however, fertilizer placement will have less impact on herbicide performance if proper herbicides are chosen and applied correctly.Index words: topdress, subdress, incorporate, large crabgrass, eclipta, spotted spurge, preemergenceChemicals used in this study: Flumioxazin (SureGuard®); 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazin-6-yl]-4,5,6,7-tetrahydro-1H-isoindole1,3(2H)-dione; Dimethenamid-P (Tower) 2-chloro-N-[(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)acetamide; Prodiamine (Barricade) 2,4-dinitro-N3, N3-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine (Barricade®)Species used in this study: Large crabgrass (Digitaria sanguinalis L.); Eclipta (Eclipta prostrata L.); Spotted spurge (Euphorbia maculata L.)

The objective of this research was to evaluate dithiopyr and isoxaben combinations and indaziflam (Marengo) for early postemergence control of woodland bittercress (Cardamine flexuosa) and yellow woodsorrel at 4 different early growth stages. Herbicides evaluated included sprayable formulations of isoxaben, dithiopyr + isoxaben, dithiopyr, indaziflam, and prodiamine + isoxaben without any surfactants. Woodland bittercress growth stages included seed production (extra-large), recently flowered (large), 6 to 9 leaf (medium) or in 2 to 5 leaf stage (small), while yellow woodsorrel growth stages included 8 to 12 leaf stage (extra-large), 4 to 6 leaf stage (large), 2 to 4 leaf stage (medium) and cotyledon to 1 leaf stage (small). Shoot fresh weight data showed all treatments provided ≤98% of woodland bittercress at the small stage. Dithiopyr + isoxaben (98%), isoxaben (90%), and indaziflam (93%) provided the highest level of woodland bittercress control at the medium stage and were the only treatments providing acceptable control (≥80%). In the large stage, dithiopyr + isoxaben provided acceptable control (80%) and outperformed other treatments. All treatments with the exception of isoxaben generally provided acceptable control of yellow woodsorrel up to the large growth stage. Only indaziflam (86% control) provided acceptable control at the extra-large stage. Index words: herbicide, postemergence weed control, container-grown plants, phytotoxic damages. Herbicides used in this study: isoxaben (Gallery® 4SC) N-[3-(1-ethyl-1-methylpropyl)- 5-isoxazolyl]-2,6-dimethoxybenzamide; dithiopyr (Dimension® 2EW) S,S'-dimethyl 2-(difluoromethyl)-4- (2-methylpropyl)-6-(trifluoromethyl)- 3,5-pyridinedicarbothioate; indaziflam (Specticle® FLO) N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-(1-fluoroethyl)-1,3,5-triazine-2,4-diamine; prodiamine + isoxaben (Gemini® SC) 2,4-dinitro-N3,N3-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine + N-[3-(1-ethyl-1-methylpropyl)- 5-isoxazolyl]-2,6-dimethoxybenzamide; dithiopyr + isoxaben (Dimension® + Gallery®) S,S'-dimethyl 2-(difluoromethyl)-4- (2-methylpropyl)-6-(trifluoromethyl)- 3,5-pyridinedicarbothioate + N-[3-(1-ethyl-1-methylpropyl)- 5-isoxazolyl]-2,6-dimethoxybenzamide. Weed species evaluated: woodland bittercress (flexuous bittercress) (Cardamine flexuosa With.); yellow woodsorrel (Oxalis stricta L.).

By definition, an invasive plant is a non-native or alien species whose introduction causes or may cause economical or environmental harm. Due to well-documented and widespread devastating impacts of invasive plants, all exotic or introduced plant species often are erroneously referred to as invasive or considered detrimental, whereas native plants may be promoted as beneficial. Although invasive plants have been the subject of a great deal of research and discussion, less attention has been placed on native plant species that can become economically important weedy pests under certain scenarios, such as in landscape plantings or agricultural production systems. The objective of this manuscript is to synthesize current literature available on native weedy plants in Florida and other Southern United States (including Alabama, Arkansas, Georgia, Louisiana, North Carolina, Mississippi, South Carolina, Tennessee, and Texas) and discuss how their biology paired with human activities, preferences, and available management practices cause these species to proliferate and be problematic. Focus is placed on nine important native weeds in residential and commercial landscape plantings, including spurges (Euphorbia spp.), woodsorrels (Oxalis spp.), saw palmetto [Serenoa repens (Bartram) Small], bracken fern [Pteridium aquilinum (L.) Kuhn], artillery weed (Pilea microphylla L.), Virginia creeper [Parthenocissus quinquefolia (L.) Planch], trumpet creeper [Campsis radicans (L.) Seem. Ex Bureau], eastern poison ivy [Toxicodendron radicans (L.) Kuntze], and pennyworts/dollarweed (Hydrocotyle spp.). Reasons these species become problematic, including fast growth and reproductive rates, lack of selective management options, and ability to thrive in the landscape environment, also are discussed.

Research was conducted to determine the tolerance of multiple native and ornamental grass species and one ornamental sedge species to over-the-top applications of the postemergence herbicide topramezone at three locations in the southeastern United States in 2016 and 2017. Fully rooted liners of selected grass species were outplanted into research plots in Apopka, FL; Dallas, TX; and Knoxville, TN in late spring, allowed time to establish (≈1–2 months) and then treated with two applications of topramezone at either 0.05 or 0.10 kg a.i./ha at 6–8 weeks intervals. Results showed that species including Andropogon virginicus (broomsedge), Schizachyrium scoparium ‘The Blues’ (little bluestem), Tripsacum dactyloides (eastern gamagrass), and Tripsacum floridanum (florida gamagrass) exhibited the greatest tolerance to topramezone with Chasmanthium latifolium (wild oats), Eragrostis elliottii ‘Wind Dancer’, Muhlenbergia capillaris (pink muhly), and Spartina bakeri (sandcord grass) were significantly injured (50% injury or greater) at both herbicide rates. Average injury observed on Panicum virgatum ‘Shenandoah’ (red switchgrass) (ranging from 39% to 100% injury) and Sorghastrum nutans (indian grass) (ranging from 0% to 40% injury) was higher in Florida than in Tennessee (injury ranging from 23% to 43% on red switchgrass and 0% to 10% on indian grass). Similarly, Pennisetum alopecuroides (dwarf fountain grass) showed higher tolerance in Texas (ranging from 0% to 34% injury) compared with those observed in Tennessee (ranging from 0% to 53% injury). Topramezone injury to Carex appalachica (appalachian sedge) was ≤18% following two applications at both rates tested. Although no injury was observed in appalachian sedge following a single application up to 0.1 kg a.i. in Florida, plants succumbed to heat stress and accurate ratings could not be taken following the second application. Because of variability observed, tolerance of red switchgrass, indian grass, dwarf fountain grass, and appalachian sedge to applications of topramezone deserves further investigation. There is potential for future use of topramezone for control of certain grass and broadleaf weeds growing in and around certain ornamental grass species. However, as there was significant variability in tolerance based on species and differences in cultivars, testing a small group of plants before large-scale application would be recommended.

Extension and research professionals in the southeastern United States formed the Southern Nursery Integrated Pest Management working group (SNIPM) to foster collaboration and leverage resources, thereby enhancing extension programming, increasing opportunity, and expanding the delivery of specialized expertise to nursery crop growers across a region. Building a productive and lasting working group requires attracting a group of research and extension faculty with complementary expertise, listening to stakeholders, and translating stakeholder needs into grant priorities to help solve problems, all hallmarks of effective teamwork principles. SNIPM has now grown to include 10 U.S. states and 11 institutions and has been awarded seven grants totaling $190,994 since 2009. A striking benefit of working group membership was observed over time: synergy. Greater awareness of individual expertise among SNIPM members, each of whom were focused on different aspects of the nursery production system stimulated multistate extension publications, electronic books (eBooks), mobile device applications (apps), popular press articles, and spin-off research projects when separate foci were combined and directed toward complex challenges. Deliverables achieved from this faculty collaboration include nine peer-reviewed publications, four manuals and books and 23 book chapters, and a combined total of 11 abstracts, conference proceedings and extension publications. To date, the return on investment for SNIPM is one deliverable produced to every $2265.89 in grant funding. SNIPM has also been honored with multiple American Society for Horticultural Science publication awards as well as the Southern Region Integrated Pest Management Center Bright Idea Award for the quality and originality of their project outputs. Continuing to work together toward common goals that bridge technology and serve the nursery industry while supporting each individual member’s program will be crucial to the long-term success of this working group.

Artilleryweed is an annual or short-lived perennial weed that is becoming increasingly problematic in nurseries and landscapes in tropical and subtropical environments. Currently, no herbicide recommendations exist for management of artilleryweed. Objectives of this trial were to evaluate PRE and POST herbicides for efficacy on artilleryweed. All studies were conducted in Apopka, FL in a shaded greenhouse. Herbicides evaluated for POST control included diquat, dimethenamid-P, flumioxazin, glufosinate, glyphosate, indaziflam, oxadiazon, pelargonic acid, sulfentrazone and sulfosulfuron applied at their highest labelled rates to mature (10 to 12 cm height) artilleryweed. For PRE experiments, pots were overseeded with artilleryweed seed and treated with dimethenamid-P, indaziflam, isoxaben, oxadiazon, oxyfluorfen+prodiamine, oxyfluorfen+pendimethalin, pendimethalin, pendimethalin+dimethenamid-P, prodiamine, prodiamine+isoxaben, S-metolachlor, or trifluralin+isoxaben. When assessing both initial fresh weight and regrowth, flumioxazin and glufosinate provided the most consistent POST control when applied at the highest labelled rate, although regrowth did occur following application with glufosinate. All PRE herbicides evaluated provided over 90% control of artilleryweed with the exception of isoxaben and trifluralin+isoxaben. Results indicate that several effective options exist for artilleryweed management, but more effective control will likely be achieved when herbicides are applied PRE.

Organic mulch is commonly used in landscape planting beds to improve plant growth and reduce competition from weed species. Although many different mulch materials have been evaluated in landscape, forestry, or agricultural settings, there have been no previous reports concerning the maintenance costs associated with different mulch materials from a weed control perspective. Trials were conducted at two locations in Florida to estimate the annual maintenance costs associated with pine bark nuggets (bark derived from pine species not specified) and pine straw mulch [mix of longleaf pine (Pinus palustris) and slash pine (Pinus taeda) needles] with and without the use of a granular preemergence herbicide when maintained at similar depths in schilling’s holly (Ilex vomitoria ‘Schilling’s Dwarf’) shrub beds and asiatic jasmine (Trachelospermum asiaticum ‘Minima’) groundcover beds. Weed coverage and residual mulch depth were tracked over time, with maximum and minimum thresholds (20% and 2 inches, respectively) set as triggers for maintenance activities. Results showed that the addition of herbicide (trifluralin + isoxaben) had little to no impact on weeding frequency or time when plots were mulched, but did reduce hand weeding frequency and time compared with nontreated, nonmulched plots. Both mulch materials used alone reduced hand weeding frequency and time compared with herbicide-only treatments. Although results varied by bed type and location, pine bark generally provided greater weed control compared with pine straw and required fewer mulch additions and less mulch by volume. Results from this study suggests that using pine bark nuggets as mulch may result in lower maintenance costs and weed pressure compared with pine straw when both are applied and maintained at 2-inch depths.

Budget reductions for the Cooperative Extension Service have made traditional extension programming (face-to-face, live programming) difficult for extension professionals. Attending traditional extension programming can also prove to be challenging for industry practitioners due to the need to delay or reschedule work activities and the need to travel to participate. The Tennessee Master Nursery Producer program (TMNP) is a professional development extension program designed to enhance the sustainability of the Tennessee nursery crops industry. The TMNP was first offered as a traditional extension program in 2012. Although the program was successful, it demanded substantial time from faculty and staff to coordinate the program, prepare presentations, and travel. Recurring travel expenses required a significant financial commitment from both extension personnel and participants. An asynchronous online program was developed to address these challenges and to increase accessibility, exploit the economies of scale, and standardize curriculum. The objective of this article is to describe the advantages and disadvantages that were identified offering nursery production subject matter as a traditional live classroom and subsequently as an asynchronous online program in terms of development cost, administrative and technological requirements, and economic impacts.

Although primarily used as an effective PRE herbicide, indaziflam has been shown to provide early POST control of some weeds commonly found in nursery production. Previous investigation on the early POST efficacy of indaziflam focused on the liquid formulation, and the ability of the granular formulation to provide early POST weed control is unknown. Nursery trials were conducted to evaluate early POST control of oxalis using two formulations of indaziflam. Oxalis seeds were surface sown to nursery containers at two separate dates and grown until they reached the two- to four-leaf stage (2-4L) and six- to eight-leaf stage. Both growth stages were treated with indaziflam at 12.6, 25.1, 50.2, and 100.4 g ai ha−1using either a granular (G) or liquid (SC) formulation. A chemical control treatment (glyphosate) and a nontreated control were also included for comparison. The SC formulation provided > 90% control of both oxalis growth stages at all four rates and was similar to glyphosate. The G formulation at 12.6 and 25.1 g ha−1only provided marginal control, but overall performed similarly to the SC formulation at the 50.2 and 100.4 g ha−1rate in most experiments. In contrast to the SC formulation, the G formulation is labeled for use over the top of container-grown nursery crops. Results of this research indicate that in areas where oxalis is the primary weed of concern, the G formulation of indaziflam could be applied to control small oxalis up to the 2-4L stage at the currently labeled rate (50.2 g ha−1).

Due to the relatively small market, volatility concerns, and high crop-value-per-acre associated with ornamental crops, no preemergence (PRE) herbicides are currently labeled for use in greenhouses containing plants. The objective of this study was to evaluate indaziflam SC for potential use as a PRE herbicide on gravel in greenhouses containing sensitive crops grown in extreme environmental conditions. Mini-greenhouses (MG) were designed and constructed to fit within gravel ground beds as an initial component to this study in order to evaluate herbicide volatility. Species evaluated included ‘Better Boy’ tomato (Lycopersicon esculentum Mill.), ‘Extreme Orange’ impatiens (Impatiens walleriana Hook. f.) and two species of petunia (Petunia × hybrida Juss. ‘Dreams White’ and ‘Dreams Neon Rose’). Indaziflam SC was applied at the manufacturer's labeled rate [40 g ai·ha−1 (0.04 lbs ai·A−1)] (1×) and at twice the labeled rate [80 g ai·ha−1 (0.07 lbs ai·A−1)] (2×). Each rate was applied using one of three different methods: 1) applied to only the gravel in ground beds with plants placed on gravel and covered with MG immediately following application; 2) applied over the top of plants on gravel inside the ground beds and covered with MG immediately application; and 3) applied over the top of plants outside the ground beds on adjacent gravel and left outside of MG. Two nontreated control treatments were maintained for each species and were placed either on nontreated gravel inside ground beds and covered with MG or placed outside ground beds on adjacent nontreated gravel and not covered with MG. Little to no injury was observed on any of the species after being placed on treated gravel and covered with a MG regardless of indaziflam rate. However when indaziflam was applied over-the-top, impatiens and tomatoes exhibited severe injury and death by 30 days after treatment (DAT). Additionally, fresh weights showed that all species receiving either over-the-top treatment were severely injured, while the plants placed on treated gravel inside the MG and both nontreated control treatments (both inside and outside of MG) exhibited no signs of injury or stunted growth. Results from this study indicate that while indaziflam may cause crop injury to ornamental species when applied over-the-top, it is likely that little to no injury will be observed as a result of volatility due to a gravel application in an enclosed structure.

Use of organic mulch is one of the most common methods of weed control in landscape planting beds and provides other benefits, including improved soil characteristics, increased growth of ornamental plants, and enhanced property aesthetics. In the landscape maintenance industry, it is common to apply mulch and herbicides concurrently to landscape beds to provide long-term, broad-spectrum weed control. It is known that herbicides behave differently when applied to different soil types and organic materials; however, research is lacking concerning which herbicides are most effective with different mulch materials in the landscape. Determining the most effective herbicide–mulch combinations could potentially improve weed control, reduce labor costs from hand weeding, and mitigate negative environmental impacts resulting from off-site herbicide movement. The objective of this paper is to review the research that has been conducted pertaining to various mulch–herbicide combinations in the landscape and in other areas of agricultural production while also identifying key knowledge gaps that should be addressed in future research. Review of the literature suggests satisfactory weed control can be achieved with high mulch depths (≥ 7 cm) regardless of herbicide use, and herbicide–mulch interactions become more pronounced as mulch depth decreases. Additionally, future research is needed to determine which herbicides are best suited for different mulch types to improve weed control and potentially reduce environmental impacts, including herbicide leaching and runoff into urban and suburban waterbodies.

Use of preemergence and postemergence herbicides is the most effective and economical method of weed control in landscape planting beds. When used correctly, herbicides can provide satisfactory weed control, reduce labor costs, and cause little or no negative environmental impacts. Major factors in herbicide efficacy include choosing the correct herbicide for the weed species present, following proper calibration procedures, and applying herbicides at the correct timing. The objective of this review is to provide a comprehensive analysis of the research pertaining to herbicide use in landscape planting beds and present 1) the advantages and disadvantages of common chemical weed control strategies, 2) the most effective preemergence and postemergence herbicides in various landscape scenarios, 3) potential environmental concerns pertaining to improper application of herbicides, and 4) highlight knowledge gaps where additional research is needed or improvements could be made.

Weed control continues to be one of the most expensive and time consuming aspects of landscape maintenance. Many homeowners are becoming more interested in nonchemical pest-management strategies due to increasing concern over the environmental impact of pesticide use. Nonchemical landscape weed control can be achieved using mechanical disruption (e.g., mowing, hand-pulling, hoeing, and tilling), physical barriers, or cultural control methods (e.g., mulching and plant selection). However, the best results are almost always achieved when employing a variety of methods (often involving chemical control methods). In adopting a weed control strategy, client expectations and weed tolerances must be addressed. While a virtually weed-free landscape is possible without the use of herbicides, this goal often requires a significant amount of time and money, and requires more planning to be successful. The goal of this manuscript is survey the literature pertaining to nonchemical weed control in landscape planting beds and determine: 1) the most effective strategies; 2) the advantages and disadvantages of common practices; and 3) highlight areas where research is needed or improvements could be made.

Three experiments were conducted to evaluate early POST control of yellow woodsorrel using PRE-applied herbicides. In experiment 1, yellow woodsorrel was seeded at two dates in a commercial pine-bark substrate and grown until reaching either the cotyledon–one-leaf (C-1L) or two- to four-leaf (2-4L) growth stage. The herbicides isoxaben, indaziflam, and dimethenamid-p were applied at these growth stages. Two rates of isoxaben and indaziflam provided yellow woodsorrel control (≥ 80% reduction in fresh weight [FW]) when applied at the C-1L stage; however, once yellow woodsorrel reached the 2-4L stage, indaziflam was the only herbicide that provided effective control at both rates tested. Experiments 2 and 3 were similar to experiment 1, except two labeled rates of dithiopyr were also evaluated. In experiment 2, all herbicides evaluated provided ≥ 90% reduction in FW of yellow woodsorrel at the C-1L stage. Although no differences in FW were observed among any of the herbicide treatments when yellow woodsorrel were treated at the 2-4L stage, control ratings indicated that indaziflam provided the most effective yellow woodsorrel control. Experiment 3 results also indicated that isoxaben, indaziflam, and dithiopyr controlled yellow woodsorrel (≥ 95% reduction in FW) when treatments were applied at the C-1L stage, whereas dimethenamid-p reduced shoot FW 70%. When yellow woodsorrel was treated after reaching the 2-4L stage, indaziflam provided the greatest control of any herbicide evaluated.

Three woody shrub species [cleyera (Ternstroemia gymnanthera Thunb. ‘Conthery’), Indian hawthorn (Rhaphiolepis indica L.) and loropetalum (Loropetalum chinensis Oliv.‘Ruby’)] were container-grown for one growing season in 2008 using either pinebark (industry standard), clean chip residual or WholeTree (derived by-products from the forestry industry) as potting substrates and then transplanted into the landscape in 2008. An Automated Carbon Efflux System was used to continually monitor soil CO2 efflux from December 2010 through November 2011 in each species and substrate combination. Changes in soil carbon (C) levels as a result of potting substrate were assessed through soil sampling in 2009 and 2011 and plant biomass was determined at study conclusion. Results showed that soil CO2-C efflux was similar among all species and substrates, with few main effects of species or substrate observed throughout the study. Soil analysis showed that plots with pinebark contained higher levels of soil C in both 2009 and 2011, suggesting that pinebark decomposes slower than clean chip residual or WholeTree and consequently has greater C storage potential than the two alternative substrates. Results showed a net C gain for all species and substrate combinations; however, plants grown in pinebark had greater C sequestration potential.

Increased trace gas emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are widely believed to be a primary cause of global warming. Agriculture is a large contributor to these emissions; however, its role in climate change is unique in that it can act as a source of trace gas emissions or it can act as a major sink. Furthermore, agriculture can significantly reduce emissions through changes in production management practices. Much of the research on agriculture’s role in mitigation of greenhouse gas (GHG) emissions has been conducted in row crops and pastures as well as forestry and animal production systems with little focus on contributions from specialty crop industries such as horticulture. Our objective was to determine efflux patterns of CO2, CH4, and N2O associated with three different fertilization methods (dibble, incorporated, and topdressed) commonly used in nursery container production. Weekly measurements indicated that CO2 fluxes were slightly lower when fertilizer was dibbled compared with the other two methods. Nitrous oxide fluxes were consistently highest when fertilizer was incorporated. Methane flux was generally low with few differences among treatments. Results from this study begin to provide data that can be used to implement mitigation strategies in container plant production, which will help growers adapt to possible emission regulations and benefit from future GHG mitigation or offset programs.

Due to concerns over future pine bark (PB) availability for container plant production, recent research has focused on evaluating suitable alternatives. For alternatives to be considered suitable substrate replacements, they must not only have desirable characteristics as a container substrate (e.g., adequate drainage, inert, pathogen free, etc.), but must also cause no negative fertility effects (e.g., nitrogen immobilization) following planting in the landscape. The study objective was to evaluate the landscape performance of three woody ornamentals grown in PB and in two alternative wood-based substrates, namely WholeTree (WT) and Clean Chip Residual (CCR). Crapemyrtle (Lagerstroemia indica × faurei ‘Acoma’), magnolia (Magnolia grandiflora ‘D.D. Blanchard’), and shumard oak (Quercus shumardii) were container grown in PB, WT, or CCR for an entire growing season prior to being planted into the landscape. Plants were grown in the landscape for two growing seasons. Data suggest that all species exhibited similar landscape performance when grown in WT or CCR compared to the PB standard. Therefore, the use of WT and CCR as alternative wood-based substrates for crapemyrtle, magnolia, and oak production may be acceptable from a landscape establishment standpoint.

Multistate collaborations enable extension professionals to reach their audience across a region with similar production challenges. The objective of this article is to introduce the three proceeding manuscripts delivered at the American Society of Horticultural Sciences annual conference in Atlanta, GA, as part of a workshop entitled “Advancing Technology Adoption and Achieving Extension Impact: A Working Group Success Story.” Topics discussed in the following manuscripts include the development of a multistate working group and the advantages associated with participation, development and impact of book or electronic book publications, and survey results from more traditional hands-on workshops. The goal of this workshop was to provide guidance to others who wish to establish multistate, multidisciplinary collaborative teams as well as use new education formats.

Four experiments were conducted to evaluate early postemergence control of spotted spurge (Chamaesyce maculata) in nursery crops using preemergence active herbicides. In Experiment 1, spotted spurge (SS) seed were overseeded at two different dates in a commercial pine bark substrate and were grown until reaching either the cotyledon to one leaf (C–1L) stage, or the two to four leaf (2–4L) stage. Herbicides applied included: Broadstar 1604 (flumioxazin), V-10142 (imazosulfuron), and Tower (dimethenamid-P). These products were applied postemergence at their respective recommended label rate (1 ×) and twice (2 ×) this rate to SS either at the C–1L stage or at the 2–4L stage. In general, V10142 and Tower provided the greatest injury to SS in the C–1L. Tower also provided greatest SS injury in the 2–4L stage. In Experiment 2, postemergence control was tested in the C1-L and 2–4L stages with Broadstar 1604, FreeHand (dimethenamid-P 0.75% + pendimethalin 1.0%), Tower, and Pendulum 3.3 EC (pendimethalin) at the 1× and 2× the label rate. FreeHand at 2×, along with Tower and Pendulum at both rates provided the highest SS injury ratings in the C–1L. Tower at 2× and Pendulum at both rates provided greatest SS injury in the 2–4L. In Experiments 3 and 4, Broadstar (1/2×, 1×, and 2× rate), Casoron (dichlobenil) (1× and 2×), HGH-63 (oxyflurfen) (1×), Certainty (sulfosulfuron) (1× and 2×), Tower (2/3× and 1×), V-10142 (1× and 2×), Pendulum 3.3 EC (1× and 2×), FreeHand (1× and 2×) were applied to SS in either C–1L or 2–4L as described above. Results from Experiments 3 and 4 indicate that Certainty (both rates), Tower (both rates), Pendulum (both rates), and FreeHand (both rates) have postemergence activity on immature SS, especially when applied in the C–1L stage. Postemergence activity declined when herbicides were applied to SS in the 2–4L, however Pendulum (both rates), Certainty (both rates), and FreeHand (2× rate) had a marginal effect.

Empirical records provide incontestable evidence for the global rise in carbon dioxide (CO2) concentration in the earth's atmosphere. Plant growth can be stimulated by elevation of CO2; photosynthesis increases and economic yield is often enhanced. The application of more CO2 can increase plant water use efficiency and result in less water use. After reviewing the available CO2 literature, we offer a series of priority targets for future research, including: 1) a need to breed or screen varieties and species of horticultural plants for increased drought tolerance; 2) determining the amount of carbon sequestered in soil from horticulture production practices for improved soil water-holding capacity and to aid in mitigating projected global climate change; 3) determining the contribution of the horticulture industry to these projected changes through flux of CO2 and other trace gases (i.e., nitrous oxide from fertilizer application and methane under anaerobic conditions) to the atmosphere; and 4) determining how CO2-induced changes in plant growth and water relations will impact the complex interactions with pests (weeds, insects, and diseases). Such data are required to develop best management strategies for the horticulture industry to adapt to future environmental conditions.

Over the past three decades, one issue that has received significant attention from the scientific community is climate change and the possible impacts on the global environment. Increased atmospheric carbon dioxide (CO2) concentration along with other trace gases [i.e., methane (CH4) and nitrous oxide (N2O)] are widely believed to be the driving factors behind global warming. Much of the work on reducing greenhouse gas emissions and carbon (C) sequestration has been conducted in row crop and forest systems; however, virtually no work has focused on contributions from sectors of the specialty crop industry such as ornamental horticulture. Ornamental horticulture is an industry that impacts rural, suburban, and urban landscapes. Although this industry may have some negative impacts on the global environment (e.g., CO2 and trace gas efflux), it also has potential to reduce greenhouse gas emissions and increase C sequestration. The work described here outlines the causes and environmental impacts of climate change, the role of agriculture in reducing emissions and sequestering C, and potential areas in ornamental horticulture container-grown plant production in which practices could be altered to increase C sequestration and mitigate greenhouse gas emissions.

Atmospheric concentrations of carbon dioxide (CO2) have significantly increased over the past century and are expected to continue rising in the future. While elevated levels of CO2 will likely result in higher crop yields, weed growth is also highly likely to increase, which could increase the incidence of herbicide resistant biotypes. An experiment was conducted in 2012 to determine the effects of an elevated CO2 environment on glyphosate and halosulfuron efficacy for postemergence control of purple and yellow nutsedge (Cyperus rotundus L. and C. esculentus L.). Both species of nutsedge where grown in 3.0-L containers under either ambient or elevated (ambient + 200 µmol mol-1) CO2 in open-top field chambers and treated with either 0.5×, 1.0×, or 1.5× of the manufacturer’s labeled rate of halosulfuron, glyphosate, or a tank mix of the two herbicides. The growth of both nutsedge species responded positively to elevated CO2, purple nutsedge had increased shoot and root dry weights and yellow nutsedge had increased shoot, root, and tuber dry weights and counts. Few treatment differences were observed among the herbicides at any of the rates tested. At three weeks following herbicide application, both purple and yellow nutsedge were adequately controlled by both herbicides and combinations at all rates tested, regardless of CO2 concentration. Based on this study, it is likely that predicted future CO2 levels will have little impact on the efficacy of single applications of halosulfuron or glyphosate for control of purple and yellow nutsedge at the growth stages described here, although scenarios demanding more persistent control efforts remain a question.

Agriculture is a large contributor of trace gas emissions and much of the work on reducing greenhouse gas (GHG) emissions has focused on row crops and pastures, as well as forestry and animal production systems; however, little emphasis has been placed on specialty crop industries such as horticulture. Our objective was to determine efflux patterns of CO2, CH4, and N2O associated with four different nursery container sizes [3.0 liter (trade gal; TG), 3.8 liter (#1; 1 gal), 7.6 liter (#2; 2 gal), and 11.4 liter (#3; 3 gal) using dwarf yaupon holly (Ilex vomitoria ‘Nana’ L.) grown under common production practices for one year. Weekly measurements indicated that carbon dioxide (CO2) and nitrous oxide (N2O) fluxes were highest in the largest containers (#3). There was a significant positive relationship between container size and CO2 efflux. Nitrous oxide efflux followed a similar pattern, except there were no differences between the two smallest container sizes. In general, CO2 and N2O fluxes increased with increasing temperature. Methane flux was consistently low and had no significant effect on total trace gas emissions. Results from this study begin to address uncertainties regarding the environmental impact of the horticulture industry on climate change while providing baseline data of trace gas emissions from container production systems needed to develop future mitigation strategies.