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S. Christopher Marble

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.

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S. Christopher Marble and Todd P. West

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.

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S. Christopher Marble, Amy Fulcher and Richard Karel

Asynchronous online extension classes, in which content is made available on demand, can reach a larger audience, offer more scheduling flexibility, and reduce the strain on limited time and financial resources for extension faculty and staff. In comparison with traditional extension programming (in-person presentations) or online synchronous programming (live webinars), asynchronous programs can require significant time and resources during the initial development stages, including advanced planning and dedicated contributors as well as ongoing information technology (IT) infrastructure and maintenance. The objective of this article is to summarize the development process and inputs needed to successfully develop an online asynchronous extension program based on the authors’ experience developing the Tennessee Master Nursery Producer Program (TMNP). The TMNP is a certificate program for nursery growers in Tennessee designed to improve growers’ long-term environmental, economic, and community sustainability. Developing the online TMNP required three key positions: project coordinator, e-learning specialist, and content developer which spent 473, 401, and 847 hours, respectively, during the development process. Detailed information on development time, requirements, and suggestions for other institutions wishing to develop similar programs is offered.

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S. Christopher Marble, Amy Fulcher and John Toman

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.

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S. Christopher Marble, Matthew T. Elmore and James T. Brosnan

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 <10% injury to no injury being evident after each application of both herbicide rates tested. 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.

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S. Christopher Marble, Andrew K. Koeser and Gitta Hasing

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.

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S. Christopher Marble, Andrew K. Koeser and Gitta Hasing

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.

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Cody J. Stewart, S. Christopher Marble, Brian J. Pearson and P. Christopher Wilson

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S. Christopher Marble, Jeff L. Sibley, Charles H. Gilliam and H. Allen Torbert

Each year, over 16 million tons of poultry litter is produced in the United States. Federal and state regulations now limit the amount of poultry litter that can be land-applied, making it difficult to store and dispose of poultry litter. The objective of this study was to evaluate composted poultry litter (CPL) as a fertilizer source for bedding plants at various rates in comparison with commercially available inorganic fertilizers in regard to plant growth and nutrient leaching. Two experiments were conducted to evaluate use of CPL as fertilizer for landscape annual bedding plants. Petunia spp. ‘Celebrity Red’ and Verbena hybrida ‘Quartz Scarlet’ were planted in raised beds simulating an urban landscape. Before planting, 10 inorganic fertilizer or CPL treatments were incorporated into the raised beds, including Peafowl® brand garden-grade fertilizer 13N–5.6P–10.9K (13-13-13) at rates of 4.9 g N/m2 and 9.8 g N/m2, Polyon® 13N–5.6P–10.9K (13-13-13) at rates of 4.9 g N/m2 and 9.8 g N/m2, and CPL at rates of 4.9 g N/m2, 9.8 g N/m2, 19.6 g N/m2, 29.4 g N/m2, 39.2 g N/m2, and 49 g N/m2. Use of CPL incorporated into landscape planting beds as a fertilizer source resulted in plants equal to or larger than plants grown with conventional inorganic fertilizers. Nitrate (NO3) and ammonia (NH4) levels in leachates from plots amended with CPL were comparable with plots amended with commercial inorganic fertilizers and nitrogen (N) levels were in most cases less in plots fertilized with CPL when compared with inorganic fertilizers when the same N rate was applied. Composted poultry litter may not be able to fully replace inorganic fertilizers, but it can reduce inorganic fertilizer requirements and provide an environmentally sound alternative to poultry waste disposal as well as provide beneficial aspects for plant growth in annual bedding plants.

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S. Christopher Marble, Andrew K. Koeser, Gitta Hasing, Drew McClean and Annette Chandler

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.