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Weed management remains a critical challenge in the U.S. container ornamental production industry, where weeds not only compete with crops for limited resources but also harbor pests and pathogens, thereby diminishing plant quality and marketability. The paper explores the economic impact of weed infestations, herbicide resistance development, and the limited availability of selective herbicides for ornamental crops in the United States. This review synthesizes current chemical weed control tactics, focusing not only on both preemergence and postemergence herbicides commonly used in ornamental nurseries, but also organic alternatives and integrated weed management (IWM) approaches as complementary strategies by evaluating their effectiveness, crop safety, and usage. There is a critical need for research in the areas of alternative chemical options such as insecticides, miticides (e.g., Zerotol and Tetra Curb Max), and organic products for liverwort control in greenhouses. Although essential oils and plant-based extracts show some potential, their effectiveness and practical use remain largely unexplored.

Weeds are undesirable plants that can interfere with human activities and can hamper crop production and practices. The competition among ornamentals and weeds for space, nutrition, light, and moisture within a restricted area, such as in container production, can be intense and destructive. In response to increasing concerns regarding herbicide injuries and the effects of pesticide use on the environment, many growers are extremely interested in non-chemical pest-management approaches. There are various non-chemical strategies to control weeds in containers, which include scouting, sanitation practices, hand weeding, mulching, irrigation management, substrate stratification, mulch discs or geo discs, lid bags, and fertilizer placement. In a restricted growth environment, weeds have been shown to reduce crop growth significantly. Limited information is available on the effects of weed densities and container sizes on ornament–weed competition within containerized production and how the concepts of fertilizer placement can be used efficiently to control weeds in containers without using any herbicides on the ornamentals. There is an immediate need to evaluate the interference and competitive effects of pernicious weed species in container-grown ornamentals in the North Central United States and to develop effective non-chemical weed control strategies by altering fertilizer placement in container production.

Use of organic mulch materials such as pinebark, pinestraw, or various hardwood chips for weed control is a common practice in residential and commercial landscapes. Mulch can inhibit weed seed germination and growth through light exclusion, acting as physical barrier, reducing available moisture to weed seeds within the mulch layer, and through release of allelochemicals that may inhibit germination or growth of some weed species. Previous and current research on allelopathic chemicals present in mulch have focused on cover crops and their residues with an emphasis on agronomic crops. These materials would not be suitable in a landscape setting due to rapid decomposition, lack of commercial availability, and little aesthetic appeal. Research is needed concerning identification, quantification, extraction, mechanism of release, persistence, selectivity, genetic regulation, and mode of action of potential allelochemicals present in mulch materials used for landscape purposes. More knowledge of these natural chemicals could aid practitioners and homeowners in the selection of mulch and identify potential new mulch materials that could be utilized in these industries. The purpose of this review is to summarize previous research pertaining to allelopathic compounds present in commonly used mulch materials and identify new potential mulch materials that could be utilized in the landscape sector based upon allelopathic properties. Current areas where additional research is needed are also identified.

Mulches have been evaluated extensively as a weed management tool in container plant production, but most research has focused on loose-fill wood-derived mulch materials, such as pine bark or wood chips. In this experiment, pine (mixed Pinus sp.) bark (PB), shredded hardwood (HW), and pine sawdust were evaluated for weed control and crop response both alone and in combination with a guar gum tackifier alongside a plastic film mulch, a paper slurry mulch, and the paper slurry mulch + PB and compared with a nonmulched, nontreated control and a single application of preemergence herbicide (oxyfluorfen + pendimethalin). Mulch materials were applied to nursery containers ranging from 7 to 25 gal at two different nurseries and at two research centers in central Florida in 2017 and 2018. Results showed that the plastic mulch provided more than a 90% reduction in hand weeding time and weed weight over a 6-month period, and similar control was achieved with PB, paper slurry + PB, and the HW treatment (64% to 91% reduction in weeding time and weed weight). No growth differences were observed with any mulch treatment in any species evaluated including ligustrum ( Ligustrum japonicum ), Chinese elm ( Ulmus parvifolia ), or podocarpus ( Podocarpus macrophyllum ).

Common ragweed (Ambrosia artemisiifolia L.) is an extremely competitive broadleaved summer annual weed found in Christmas tree production systems within Michigan. Common ragweed has been reported to have resistance to glyphosate, PSII inhibitors, PPO inhibitors, and ALS herbicides. There have been reports from Michigan Christmas tree growers of common ragweed resistance to clopyralid, a synthetic auxin herbicide, in Montcalm County, Michigan. The objective of this study was to test alternative post-emergence herbicide combinations and organic mulch on clopyralid-resistant common ragweed for weed control efficacy. The following two stages of common ragweed were used: stage 1 (6–9 leaves) and stage 2 (12–14 leaves). For common ragweed in stage 1 in 2021 and 2022, as well as stage 2 in 2022, at all evaluation dates, mulch + clopyralid + oxyfluorfen provided the highest level of weed control. For stage 1 in 2022, this treatment combination provided 100% control from 2 weeks after treatment (WAT) and always showed better or equal weed control compared to all the other treatments. The combination of mulch + clopyralid + glyphosate provided 100% control by 2 WAT when plants were treated at stage 2 in 2022. For the plants treated at stage 1 in 2022, many of the treatments reached a fresh weight of 0 g, but in 2021, those same treatments resulted in a fresh weight of around 20 g. Based on fresh weight, the greatest plant growth occurred with glyphosate treatment in 2021 and clopyralid and mulch alone in 2022. This is likely due to common ragweed’s resistance to these herbicides.

Climate change, driven by rising atmospheric carbon dioxide (CO 2 ), increasing temperatures, and shifting precipitation patterns, is profoundly impacting agricultural systems worldwide. These environmental changes significantly affect weed growth, distribution, and management, posing challenges across agronomic, horticultural, and ornamental crops. This review explores the impacts of climate change on weeds, focusing on the differential responses of C 3 and C 4 weed species to elevated CO 2 , higher temperatures, and drought stress. It also examines how these climatic factors influence weed management practices, particularly herbicide efficacy. While much research has focused on agronomic crops, ornamental crop productions remain underexplored, despite their unique challenges. Ornamental production systems often involve diverse plant species grown in confined spaces, making weed management more complex and sensitive to herbicide residues. These challenges are compounded by the adaptability and invasiveness of weeds under changing climatic conditions. The review highlights critical knowledge gaps, particularly the limited understanding of how climatic factors impact weed physiology and herbicide performance in ornamental settings. Addressing these gaps is essential to develop climate-resilient strategies for sustainable weed management across diverse agricultural systems.

Common liverwort ( Marchantia polymorpha ) is a primitive, spore-bearing bryophyte that thrives in containerized ornamental crop propagation and production environments. It is one of the major weed problems in container nurseries and greenhouses because it competes with ornamental plants for soil/growing medium, nutrients, water, space, and oxygen within the container. As a result, its presence can reduce the overall quality and market value of the ornamental crop. Once established in nurseries and greenhouses, it spreads rapidly because of its ability to propagate both asexually and sexually. Currently, no effective methods of controlling common liverwort in container production systems are available because a significant knowledge gap exists. Therefore, research is needed to determine whether organic mulches (types, depths, moisture holding capacity, and particle size), biopesticides, and strategic placement of fertilizers within containers suppress or inhibit common liverwort growth and development. In addition, newer chemicals (both synthetic and organic) and combinations need to be tested on different growth stages of common liverwort. The objective of this review was to summarize previous and current research related to common liverwort control in container production, and to identify areas where additional research is needed either to improve current control methods or to develop new ones.

Liverwort ( Marchantia polymorpha ) is a problematic weed in ornamental crop production. The major limitation of liverwort control is lack of herbicide options inside greenhouses and their potential to cause injury. The current research was undertaken to study the effectiveness of allelopathic properties of six different organic mulches including rice hull (RH), cocoa hull (CH), pine bark (PB), maple leaf (ML), shredded cypress (SC), and red hardwood (HW) for liverwort control. Mulch extracts were prepared and used to impregnate agar media at an increasing dose at 1X (2 mL mulch extract), 2X (4 mL), 3X (6 mL), and 4X (8 mL) rates, in a randomized complete block design. Ten liverwort gemmae were transferred to each petri dish and they were maintained inside a growth chamber. The number of gemmae germinating in each petri dish after 1 week and gemmae surviving at the end of 2 weeks was recorded. In greenhouse study, mulch extracts were applied to containers filled with substrate for assessing liverwort control. The mulch extracts or no extract (control) were applied to the containers uniformly at 1X (15 mL), 2X (30 mL), 3X (45 mL) or 4X (60 mL) rates, in a randomized complete block design. The percentage of substrate surface covered by liverwort thalli was visually estimated bi-weekly for 10 weeks. Fresh biomass of the thalli and gemmae cup counts in each pot were also recorded. After 1 week in the growth chamber, ML followed by SC, PB and RH extracts showed maximum suppression of liverwort gemmae germination. At 2 weeks, ML applied at either of the rates provided complete inhibition of liverwort growth. In greenhouse, all the mulch extracts were able to provide complete liverwort control for the first two weeks. All the mulches and rates of applications were significantly different from the control after 6, 8, and 10 weeks. PB and HW mulches showed excellent liverwort control and minimum fresh biomass of liverwort after 10 weeks as compared to other mulches. The allelopathic potential of the organic mulches can be a promising option for biopesticidal control of liverwort and a component of integrated liverwort management.

Environmental concerns are closely associated with economic activities. Without considering economic and social impacts, any policy to reduce environmental degradation becomes futile. Environmental economics is an expanding area that searches for solutions to environmental problems in tandem with the consideration of economic development. This book provides an overview of the environment-economy interface, natural resources, environmental valuation and examples of environmental policies. It contains case studies, short descriptions of current issues of global importance and international initiatives for the environment. The book's primary objective is to make the readers aware of the interdependence between environment and economics. Young students, trainees, teachers and academicians will find this book useful as an introduction to environmental economics.

Liverwort (Marchantia polymorpha) competes for resources within containers, resulting in a reduction in the quality and market value of ornamentals. Therefore, the objective of this study was (1) to assess the impact of different mulch types, depths, and their moisture-holding-capacity on liverwort control and (2) to quantify if phytotoxicities develop on ornamental plants due to the mulches. The percent water retention of four different organic mulches [rice hull (RH), cocoa hull (CH), pine bark (PB), or red hardwood (HW)] was determined in a laboratory experiment. In a greenhouse experiment, the Hosta plantaginea (Plantain Lily) varieties ‘Curly Fries’ and ‘Pandora’s Box’ were mulched with either RH, HW, CH, or PB at a depth of 0.63, 1.27, 2.54, or 5.08 cm. Liverwort thalli coverage on the container surface was visually estimated bi-weekly, and the fresh weight of the thalli was recorded at the end of the experiment. The results indicated that CH mulch retained the highest amount of moisture (86%). The RH and HW mulches, at depths of 1.27 cm or more, provided excellent (>80%) liverwort control in ‘Curly Fries’. All mulches at depths of 1.27 cm or more showed excellent (100%) liverwort control for ‘Pandora’s Box’. Overall, RH and PB mulches at all depths provided excellent liverwort control and no reduction in the growth of ‘Curly Fries’ and ‘Pandora’s Box’.