Abstract
Wildflowers attract wildlife, increase pollinator habitat, and enhance the aesthetic value of the landscape. Wildflower establishment is increasingly part of an effort to reduce maintained turfgrass on golf courses, lawns, and other maintained environments. Weed competition decreases wildflower establishment and results in poor long-term stands. Research was conducted in a controlled environment to investigate the tolerance of wildflower species to common postemergence herbicides. Wildflower species included California poppy (Eschscholzia californica Cham.), common sunflower (Helianthus annuus L.), cornflower (Centaurea cyanus L.), garden coreopsis (Coreopsis lanceolata L.), partridge pea [Chamaecrista fasciculata (Michx.) Greene], plains coreopsis (Coreopsis tinctoria Nutt.), purple coneflower [Echinacea purpurea (L.) Moench], rosering gaillardia (Gaillardia pulchella Foug.), and violet prairie clover (Dalea purpurea Vent.). Herbicides evaluated were fluazifop at 0.28 kg⋅ha–1 a.i., mesotrione at 0.14 kg⋅ha–1 a.i., clopyralid at 0.29 kg⋅ha–1 a.i., bentazon at 0.56 kg⋅ha–1 a.i., halosulfuron at 0.053 kg⋅ha–1 a.i., and imazaquin at 0.42 kg⋅ha–1 a.i. An untreated check was included for comparison. Excessive damage (≥ 53% phytotoxicity) was observed on all wildflower species in response to clopyralid, except for California poppy. Fluazifop and bentazon were relatively safe (≤ 19% phytotoxicity, regardless of herbicide) on all wildflower species; however, bentazon resulted in ≥ 40% aboveground biomass reduction in several species. Common sunflower and garden coreopsis were susceptible to halosulfuron (37% and 73% phytotoxicity, respectively) and imazaquin (37% and 87% phytotoxicity, respectively), but on all other wildflower species, phytotoxicity was ≤ 18%. Although both halosulfuron and imazaquin only resulted in ≤ 18% phytotoxicity to purple coneflower, a 43% to 44% aboveground biomass reduction was recorded. Mesotrione was only safe on California poppy and cornflower (≤ 11% phytotoxicity and ≤ 24% aboveground biomass reduction). Results suggest high tolerance variability across herbicides and species considered, but may prompt new investigation of safety and utility within field and production scenarios.
Worldwide declines in the abundance and diversity of insect pollinators are well documented (Biesmeijer et al. 2006; Kleijn et al. 2015; Potts et al. 2010; Steffan-Dewenter et al. 2005; Thomann et al. 2013). Although focus is often placed on bees, populations of other insect pollinators such as butterflies, moths, and beetles have also decreased (Cameron et al. 2011; Fox 2013; Goulson et al. 2015; Haaland et al. 2011; Wallisdevries et al. 2012). Reductions in insect pollinators impact global biodiversity, and affect negatively the productivity of agronomic crops (Gallai et al. 2009; Garibaldi et al. 2009; Kevan and Phillips 2001; Thomann et al. 2013) and the reproduction capability of a substantial number of native plants (Ashman et al. 2004; Kearns et al. 1998; Thomann et al. 2013). Habitat loss is a key contributor to insect pollinator declines (Winfree et al. 2009).
Although numerous initiatives have been implemented in recent years to curb the continued decline of pollinator insects, the introduction of wildflower habitats in and around maintained landscapes has led to substantial increases in pollinator density, diversity, and pollination services (Blaauw and Isaacs 2014a; Braman et al. 2002; Frank and Shrewsbury 2004; Haaland et al. 2011; Korpela et al. 2013; Williams et al. 2015). However, the presence of wildflowers aids much more than just pollinators. Conservation of diverse landscapes attracts natural predators that contribute to biological-based pest management and landscape resilience (Blaauw and Isaacs 2014b; Braman et al. 2002; Frank and Shrewsbury 2004; Gontijo et al. 2013; Tooker and Hanks 2000) or become a food resource for birds and other wildlife (Vickery et al. 2002, 2009; Wratten et al. 2012). Floral plantings may also increase the aesthetic value of the landscape by adding color and texture, or create a transition between manicured landscapes and unmanaged ecosystems (Ahern et al. 1992; Benvenuti 2014; Bretzel et al. 2016; Scott 2008).
A 2015 survey conducted by the Environmental Institute for Golf (funded by the United States Golf Association) concluded that 46% of all respondents reported an increase in the total acreage of natural areas on their golf courses during the past 10 years, whereas only 5% reported a decrease (Gelernter et al. 2017). These natural areas are typically comprised of heterogeneous grasslands that often contain combinations of native or commercially available grasses, forbs, and wildflowers (Gelernter et al. 2017). Efforts to convert managed turfgrass or disturbed habitats to natural areas on golf courses have been propelled by the numerous environmental benefits that can be conferred through their conservation. Managing areas as pollinator habitats may improve soil quality by limiting soil erosion and decreasing leaching of excess nitrogen (Nearing et al. 2005; Wratten et al. 2012), while protecting water quality by mitigating runoff of soils, fertilizers, and pesticides (Environmental Institute for Golf 2016; Wratten et al. 2012). Additional benefits may include reduced labor, fuel, and other inputs associated with intensively managed turfgrass (Ahern et al. 1992; Environmental Institute for Golf 2016; Nelson 1997).
Wildflowers are often established on previously disturbed land containing mixtures of native, nonnative, and often invasive vegetation. Site preparation typically consists of a postemergence application of a nonselective herbicide, followed weeks later by cultivation and debris removal (Frances et al. 2010). Wildflowers are often propagated by seed, so use of preemergence herbicides at seeding can reduce establishment and decrease stand density. The use of postemergence herbicides during establishment may limit weed interference; however, the overall tolerance of wildflowers to applied herbicides is largely unexplored.
Wildflower growth and establishment was most successful when competition for light, space, water, and nutrients from invasive grasses was reduced (Ahern et al. 1992). Minimal research has been conducted on the tolerance of wildflowers to postemergence herbicides, and studies have focused predominantly on monocot-specific chemistries such as the acetyl coenzyme A carboxylase inhibiting aryloxyphenoxypropionates and cyclohexanediones, which are uniquely well tolerated by most dicotyledonous species. Evaluation of wildflower tolerance to herbicides when grown in a greenhouse would eliminate negative effects of weed competition or environmental conditions. Therefore, the objective of our research was to evaluate the tolerance of several commonly planted wildflower species to both monocot- and dicot-specific herbicides in a controlled environment.
Materials and Methods
Greenhouse experiments.
Research was conducted at the Athens Turfgrass Research and Education Center greenhouse complex (lat. 33.54°N, long. 83.22°W) in Athens, GA, during Summer and Fall 2017. California poppy (Eschscholzia californica Cham.), common sunflower (Helianthus annuus L.), cornflower (Centaurea cyanus L.), garden coreopsis (Coreopsis lanceolata L.), partridge pea [Chamaecrista fasciculata (Michx.) Greene], plains coreopsis (Coreopsis tinctoria Nutt.), purple coneflower [Echinacea purpurea (L.) Moench], rosering gaillardia (Gaillardia pulchella Foug.), and violet prairie clover (Dalea purpurea Vent.) (Applewood Seed Co., Golden, CO, USA) were seeded at 25 kg⋅ha–1 into 15.2-cm circular pots containing a perlite-free grower-grade Canadian sphagnum peatmoss potting media (Sun Gro Horticulture, Agawam, MA, USA) on 12 May 2017 and 14 Sep 2017. Wildflower species were selected based on their high frequency of incorporation into common pollinator seed mixtures. Only common sunflower was thinned to six plants per pot after germination. Fertilizer (7N–7P2O5–7K2O) (Grigg Seven Iron; Brandt Consolidated, Inc., Springfield, IL, USA) was applied at the time of seeding at a rate of 25 kg⋅ha–1 nitrogen. Greenhouse temperatures were maintained at 29/25 °C (day/night) with average midday (1200 and 1300 HR) solar radiation ranging from 636 to 754 µmol⋅m–2⋅s–1. Irrigation was supplied through an overhead irrigation system calibrated to deliver ∼3.8 cm of water per week. Wildflower species were allowed to grow for ∼5 weeks before herbicide application.
Treatments were arranged in a 9 × 7 factorial (nine wildflower species × seven herbicide treatments) within a randomized complete block design with five replications repeated twice in time (two experimental runs). Experimental blocks were arranged along a gradient created by the greenhouse cooling pads and associated fans. Herbicides were applied once per experimental run using a carbon dioxide pressurized spray chamber (Generation III Spray Booth; DeVries Manufacturing, Inc., Hollandale, MN, USA) equipped with an XR8002VS nozzle tips (Teejet, flat-fan extended-range spray tips; Spraying Systems Company, Glendale Heights, IL, USA) calibrated to deliver 375 L⋅ha–1 at 221 kPa. Treatments were applied on 16 Jun 2017 (run 1) and 19 Oct 2017 (run 2) and consisted of fluazifop (Fusilade II; Syngenta Crop Protection, LLC, Greensboro, NC, USA) at 0.28 kg⋅ha–1 a.i., mesotrione (Tenacity, Syngenta Crop Protection, LLC) at 0.14 kg⋅ha–1 a.i., clopyralid (Lontrel; Corteva Agriscience, Wilmington, DE, USA) at 0.29 kg⋅ha–1 a.i., bentazon (Basagran; BASF Corp., Research Triangle Park, NC, USA) at 0.56 kg⋅ha–1 a.i., halosulfuron (Sedgehammer; Gowan Company, Yuma, AZ, USA) at 0.053 kg⋅ha–1 a.i., and imazaquin (Scepter T&O 70 WDG; AMVAC Chemical Corp., Newport Beach, CA, USA) at 0.42 kg⋅ha–1 a.i. Herbicide rates were chosen based on label restrictions and weed control spectrum. No surfactants were added to any treatment to minimize potential phytotoxicity. A untreated check was included for comparison. Wildflower species were at the following heights at the time of herbicide application: California poppy, 15.2 to 16.5 cm; common sunflower, 25.4 to 35.6 cm; cornflower, 17.8 to 20.3 cm; garden coreopsis, 15.2 to 19.1 cm; partridge pea, 14.0 to 15.2 cm; plains coreopsis, 30.5 to 35.6 cm; purple coneflower, 11.4 to 14.0 cm; rosering gaillardia, 14.0 to 15.2 cm; and violet prairie clover, 6.4 to 7.6 cm.
Data collection and analysis.
Analysis of variance was performed using the general linear models procedure (PROC GLM) in SAS (version 9.2; SAS Institute, Cary, NC, USA) using the appropriate expected mean square values described by McIntosh (1983). Means were separated using Fisher’s protected least significant difference test at α = 0.05. All data were arcsine square root–transformed before analysis to stabilize variance (Bowley 2008). Interpretations were not different from nontransformed data; therefore, nontransformed means are presented for clarity.
Results and Discussion
Experimental run-by-treatment interactions were not detected (F = 0.49, P = 0.87) for wildflower species phytotoxicity; therefore, data were pooled across experimental runs. A significant wildflower species (F = 43.5, P ≤ 0.0001) and herbicide main effect (F = 1.17, P = 0.02) was observed for percent phytotoxicity 3 WAT (Table 1). Experimental run-by-treatment interactions were not detected (F = 1.06, P = 0.63) for wildflower species aboveground biomass; therefore, data were pooled across experimental runs. A significant wildflower species (F = 2.23, P = 0.001) and herbicide main effect (F = 27.8, P ≤ 0.0001) was observed for aboveground biomass 3 WAT (Table 2). Experimental run-by-treatment interactions were not detected (F = 0.86, P = 0.74) for wildflower species aboveground biomass reduction; therefore, data were pooled across experimental runs. A significant wildflower species (F = 15.21, P ≤ 0.0001) and herbicide main effect (F = 108.68, P ≤ 0.0001) was observed for aboveground biomass reduction 3 WAT (Table 3).
Wildflower species phytotoxicity 3 weeks after treatment in response to postemergence herbicides applied in the greenhouse in Athens, GA, in 2017.i
Harvested aboveground biomass of wildflower species 3 weeks after treatment in response to postemergence herbicides applied in the greenhouse in Athens, GA, in 2017.i
Harvested aboveground biomass reduction of wildflower species 3 weeks after treatment in response to postemergence herbicides applied in the greenhouse in Athens, GA in 2017.i
Fluazifop applications resulted in ≤ 3% phytotoxicity 3 WAT, regardless of wildflower species (Table 1). This coincided with similar aboveground biomass as the untreated check (except for garden coreopsis and common sunflower) (Table 2) and only resulted in ≤ 8% aboveground biomass reduction compared with the untreated check for all wildflower species except for California poppy (Table 3). This was expected because fluazifop is typically used for the control of annual and perennial grass weeds in dicot cropping systems. Similarly, Olszyk et al. (2013) observed little to no response of several forb, species including western buttercup (Ranunculus occidentalis Nutt.), sicklekeel lupine (Lupinus albicaulis Douglas), farewell to spring [Clarkia amoena (Lehm.) A. Nelson & J.F. Macbr.], common madia (Madia elegans D. Don ex Lindl.), heal-all (Prunella vulgaris L.), and slender cinquefoil (Potentilla gracilis Douglas ex Hook.) to fluazifop at 0.28 kg⋅ha–1 a.i. Blake et al. (2012) also reported minimal to no phytotoxicity as well as no reduction in plant biomass of nine wildflower species when treated with a similar rate of fluazifop postemergence.
California poppy and cornflower were the only wildflower species that exhibited tolerance to mesotrione 3 WAT (5% and 11% phytotoxicity, respectively) (Table 1). However, mesotrione applications still resulted in 24% to 27% aboveground biomass reductions within these same species, respectively (Table 3). Contrarily, York and Seagroves (2008) reported 62% injury for cornflower and 53% injury for California poppy 3 WAT in response to mesotrione at 0.11 kg⋅ha–1 a.i. Although mesotrione in their study was applied at a lower rate (0.11 kg⋅ha–1 a.i. vs. 0.14 kg⋅ha–1 a.i. in our study), the addition of a crop oil concentrate may have caused more injury to plants examined in their research. All other wildflower species expressed 20% to 45% phytotoxicity and reductions in aboveground biomass of 39% to 58% (Tables 1–3). York and Seagroves (2008) noted even greater injury (59%–71%) for plains coreopsis, Gaillardia sp., and garden coreopsis in response to mesotrione 3 to 5 WAT.
Clopyralid only caused 3% phytotoxicity 3 WAT when applied to California poppy, but resulted in 53% to 94% phytotoxicity (almost complete death) for all other wildflower species (Table 1). Aboveground biomass was only reduced 9% in California poppy, but ≥ 41% in the other wildflower species (Table 3). York and Seagroves (2008) observed slightly higher phytotoxicity (19%) of California poppy 4 WAT when subjected to a lower rate of clopyralid (0.11 kg⋅ha–1 a.i. vs. 0.29 kg⋅ha–1 a.i. in our study); however, a nonionic surfactant was added to the mixture. They also observed unacceptable phytotoxicity (56%–75%) in a Gaillardia sp., garden coreopsis, cornflower, and plains coreopsis. Partridge pea was the most sensitive wildflower species to clopyralid (94% phytotoxicity and 72% aboveground biomass reduction) in our research (Table 3). Similarly, Meyer and Bovey (1991) observed reductions in partridge pea cover of 83% to 100% in multiple trial locations in response to clopyralid at 0.28 kg⋅ha–1 a.i.
Bentazon was well tolerated by most wildflower species (partridge pea, purple coneflower, violet prairie clover, rosering gaillardia, and California poppy were similar to the untreated check; ≤ 5% phytotoxicity) whereas the greatest phytotoxicity was observed on common sunflower and garden coreopsis (14% and 19%, respectively) 3 WAT (Table 1). Moderate aboveground biomass reductions (40%–44%) were observed on plains coreopsis, purple coneflower, and common sunflower, whereas ≤ 26% reductions were observed in the remainder of wildflower species (Table 3). Although bentazon resulted in no phytotoxicity to violet prairie clover, a 26% reduction in aboveground biomass was observed. This was slightly higher than the stunting (≤ 14%) recorded on ‘Durana’ white clover (Trifolium repens L.) by Basinger and Hill (2021) 10 WAT with a higher rate of bentazon (0.84 kg⋅ha–1 a.i. vs. 0.56 kg⋅ha–1 a.i. in our study).
Halosulfuron was most injurious to garden coreopsis (73% phytotoxicity) and common sunflower (37% phytotoxicity) 3 WAT (Table 1). This resulted in a 45% and 37% reduction in aboveground biomass of these same species, respectively (Table 3). All other species resulted in ≤ 16% phytotoxicity in response to halosulfuron. This coincided with ≤ 13% aboveground biomass reduction for those same species, except purple coneflower, which resulted in a 43% reduction. Although applied at a higher rate (0.14 kg⋅ha–1 a.i. vs. 0.053 kg⋅ha–1 a.i. in our study), Wiese et al. (2011) also reported halosulfuron safety on white prairie clover (Dalea candida Michx. Ex Willd.) 20 d after treatment. However, a 90% chance of phytotoxicity in response to halosulfuron was predicted (according to the Monte Carlo simulation) for blanketflower (Gaillardia aristata Pursh), as well as a reduction in biomass compared with the untreated check (Wiese et al. 2011). This was much greater than the phytotoxicity observed on rosering gaillardia (19%) in our research, but may also be related to the higher halosulfuron use rate.
Imazaquin resulted in a similar response as halosulfuron, with the highest phytotoxicity (87% and 37%) observed in garden coreopsis and common sunflower, respectively; however, the greatest aboveground biomass reduction (57% and 44%) was recorded in garden coreopsis and purple coneflower, respectively, 3 WAT (Tables 1–3). All other wildflower species exhibited ≤ 18% phytotoxicity and ≤ 23% aboveground biomass reduction in response to imazaquin. McCurdy et al. (2013) reported a differential response among Trifolium species to imazaquin at 5.6 g⋅100 m–2 a.i. plus a nonionic surfactant. Control of white clover, crimson clover (Trifolium incarnatum L.), ball clover (Trifolium nigrescens Viv.), and small hop clover (Trifolium dubium Sibth) in the field was 50%, 62%, 80%, and 91%, respectively, 6 WAT with imazaquin. This coincided with a height reduction in small hop clover of 88%, whereas height was reduced ≤ 47% for all other Trifolium species Although applied preemergence, Beran et al. (1999) reported no significant reduction in percent emergence and flower density of purple coneflower and blanketflower compared with the untreated check in response to imazaquin at 70 g⋅ha–1 a.i.
Clopyralid phytotoxicity was ≥ 53% for all but one wildflower sp., California poppy, which was tolerant to all herbicides tested. Fluazifop and bentazon were relatively safe (≤ 3% and ≤ 19% phytotoxicity, respectively) on all wildflower species; however, bentazon resulted in ≥ 40% aboveground biomass reduction in several species. These two herbicides may provide effective grass and immature broadleaf weed control, respectively. Common sunflower and garden coreopsis were susceptible to halosulfuron (37%–73% phytotoxicity) and imazaquin (37%–87% phytotoxicity), but all other wildflower species resulted in ≤ 18% phytotoxicity to these same chemistries. Although both halosulfuron and imazaquin only resulted in ≤ 18% phytotoxicity to purple coneflower, a 43% to 44% aboveground biomass reduction was recorded in response to both herbicides. Annual and perennial sedge and broadleaf weed species are often controlled with these two herbicides. Mesotrione was only safe on California poppy and cornflower (≤ 11% phytotoxicity and ≤ 24% aboveground biomass reduction); however, this herbicide may provide preemergence and postemergence control of weeds.
Wildflower plants that exist in nature are often subjected to different environmental conditions (moisture, temperature, light intensity/quality, etc.) than those propagated in a controlled environment. Greenhouse conditions are maintained to promote optimal plant growth and health; therefore, wildflower species grown in controlled environments may exhibit morphological and physiological characteristics that are more conducive to herbicide absorption, translocation, and subsequent activity (phytotoxicity and growth reduction). For example, clopyralid applied postemergence to Canada thistle [Cirsium arvense (L.) Scop] at 65% relative humidity was absorbed and translocated more (80% and 55%, respectively) than when it was applied at 35% relative humidity (60% and 45%, respectively) (Kloppenburg and Hall 1990). Therefore, less phytotoxicity and plant biomass reduction may occur when wildflower species are subjected to herbicides in field plantings. Wirestem muhly [Muhlenbergia frondosa (Poir.) Fern.] control was 98% 4 WAT in response to glyphosate (0.42 and 0.84 kg⋅ha–1) applied in the greenhouse, but only 60% to 87% in the field (Lingenfelter and Curran 2007). Similarly, Cooper et al. (2016) reported 100% bermudagrass [Cynodon dactylon (L.) Pers.] control after sequential applications of metamifop (0.3–0.5 kg⋅ha–1 a.i.) applied in the greenhouse, whereas Doroh et al. (2011) only observed 36% bermudagrass control in the field in response to sequential applications of metamifop at 0.4 kg⋅ha–1 a.i. Future research should evaluate herbicide response in the field when wildflower species are grown as monocultures and mixed stands under a variety of environmental conditions and/or geographies.
Initial wildflower establishment from seed is often unsuccessful; therefore, herbicides are important for the reduction of weed competition and subsequent promotion of successional wildflower establishment through seed and vegetative propagules. Angelella et al. (2019) observed 9% wildflower establishment of a pollinator refuge habitat during the first year, but 49% wildflower cover by the end of year 2. In general, little is known regarding herbicide use within mixed-wildflower meadow establishment. Practitioners must consider whether existing stands of turfgrass species will be included intentionally as a component of the meadow, or whether they should be removed before or during succession toward a native or naturalized stand. Weed species communities within these locations may also shift over time, further complicating control and herbicide selection and safety. Grasses dominated the landscape during the first year of pollinator habitat establishment by Angelella et al. (2019) and averaged 89% cover. However, a shift in weed species dynamics during year 2 resulted in 55% broadleaf cover and only 15% grass cover.
Fluazifop, as with other acetyl coenzyme A carboxylase–inhibiting “grass herbicides” is a novel means of controlling or suppressing grasses within broadleaf crops and meadow mixtures. Love et al. (2016), and others, have proposed a “grass-first” strategy for the establishment of urban wildflower meadows, whereby grasses are established before the introduction of wildflower species This strategy allows for suppression of nuisance weeds with broadleaf herbicides before introduction of sensitive, intentionally included wildflowers. The mixture of grasses should be considered for tolerance to a chosen grass herbicide, but the utility of grass removal and thinning is an added value of grass herbicides to manipulate succession and stand establishment.
Other herbicides considered within this study offer a range of options for manipulation of sward complexity, but none are a panacea for general weed control within mixed meadows. A tailored approach for each scenario will be required and, undoubtedly, nonselective herbicides or hand-removal will be required for the control of some nuisance weeds.
References Cited
Ahern J, Niedner CA & Barker A. 1992 Roadside wildflower meadows: Summary of benefits and guidelines to successful establishment and management 46 53 Kassabian N, Tobias A, Crayton L & Solomon N Transportation research record, no. 1334, planning, administration, and environment: Maintenance of pavement, lane markings, and roadsides.Transportation Research Board, NRC Washington, DC, USA
Angelella GM, Stange L, Scoggins HL & O’Rourke ME. 2019 Pollinator refuge establishment and conservation value: Impacts of seedbed preparations, seed mixtures, and herbicides HortScience.54 445 451 https://doi.org/10.21273/HORTSCI13600-18
Ashman TL, Knight TM, Steets JA, Amarasekare P, Burd M, Campbell DR, Dudash MR, Johnston MO, Mazer SJ, Mitchell RJ & Morgan MT. 2004 Pollen limitation of plant reproduction: Ecological and evolutionary causes and consequences Ecology.85 2408 2421
Basinger NT & Hill NS. 2021 Establishing white clover (Trifolium repens) as a living mulch: Weed control and herbicide tolerance Weed Technol.35 845 855 https://doi.org/10.1017/wet.2021.45
Benvenuti S. 2014 Wildflower green roofs for urban landscaping, ecological sustainability and biodiversity Landsc Urban Plan.124 151 161 https://doi.org/10.1016/j.landurbplan.2014.01.004
Beran DD, Gaussoin RE & Masters RA. 1999 Native wildflower establishment with imidazolinone herbicides HortScience.34 283 286 https://doi.org/10.21273/HORTSCI.34.2.283
Biesmeijer JC, Roberts SP, Reemer M, Ohlemüller R, Edwards M, Peeters T, Schaffers AP, Potts SG, Kleukers RJMC, Thomas CD & Settele J. 2006 Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands Science.313 351 354 https://doi.org/10.1126/science.1127863
Blaauw BR & Isaacs R. 2014a Flower plantings increase wild bee abundance and the pollination services provided to a pollination-dependent crop J Appl Ecol.51 890 898 https://doi.org/10.1111/1365-2664.12257
Blaauw BR & Isaacs R. 2014b Larger patches of diverse floral resources increase insect pollinator density, diversity, and their pollination of native wildflowers Basic Appl Ecol.15 701 711 https://doi.org/10.1016/j.baae.2014.10.001
Blake RJ, Westbury DB, Woodcock BA, Sutton P & Potts SG. 2012 Investigating the phytotoxicity of the graminicide fluazifop-P-butyl against native UK wildflower species Pest Manag Sci.68 412 421 https://doi.org/10.1002/ps.2282
Bowley SR. 2008 A hitchhiker’s guide to statistics in plant biology 2nd ed Any Old Subject Books Ontario, Canada
Braman SK, Pendley AF & Corley W. 2002 Influence of commercially available wildflower mixes on beneficial arthropod abundance and predation in turfgrass Environ Entomol.31 564 572
Bretzel F, Vannucchi F, Romano D, Malorgio F, Benvenuti S & Pezzarossa B. 2016 Wildflowers: From conserving biodiversity to urban greening—A review Urban For Urban Green.20 428 436 https://doi.org/10.1016/j.ufug.2016.10.008
Cameron SA, Lozier JD, Strange JP, Koch JB, Cordes N, Solter LF & Griswold TL. 2011 Patterns of widespread decline in North American bumble bees Proc Natl Acad Sci USA.108 662 667 https://doi.org/10.1073/pnas.1014743108
Cooper T, Beck LL, Straw CM & Henry GM. 2016 Efficacy of metamifop for the control of common bermudagrass HortTechnology.26 394 398 https://doi.org/10.21273/HORTTECH.26.4.394
Doroh MC, McElroy JS & van Santen E. 2011 Evaluation of new aryloxyphenoxypropionate herbicides for control of bermudagrass in zoysiagrass Weed Technol.25 97 102 https://doi.org/10.1614/WT-D-10-00104.1
Environmental Institute for Golf 2016 BMP performance goals https://www.gcsaa.org/uploadedfiles/Course/Environment/EIFG-best-management-practice-performance-goals.pdf. [accessed 26 Aug 2022]
Fox R. 2013 The decline of moths in Great Britain: A review of possible causes Insect Conserv Divers.6 5 19 https://doi.org/10.1111/j.1752-4598.2012.00186.x
Frances AL, Reinhardt Adams C & Norcini JG. 2010 Importance of seed and microsite limitation: Native wildflower establishment in non-native pasture Restor Ecol.18 944 953 https://doi.org/10.1111/j.1526-100X.2009.00629.x
Frank SD & Shrewsbury PM. 2004 Effect of conservation strips on the abundance and distribution of natural enemies and predation of Agrotis ipsilon (Lepidoptera: Noctuidae) on golf course fairways Environ Entomol.33 1662 1672
Frans R, Talbert R, Marx D & Crowley H. 1986 Experimental design and techniques for measuring and analyzing plant responses to weed control practices 29 46 Camper ND Research methods in weed science 3rd ed Southern Weed Science Society Madison, WI, USA
Gallai N, Salles JM, Settele J & Vaissière BE. 2009 Economic valuation of the vulnerability of world agriculture confronted with pollinator decline Ecol Econ.68 810 821 https://doi.org/10.1016/j.ecolecon.2008.06.014
Garibaldi LA, Aizen MA, Cunningham S & Klein AM. 2009 Pollinator shortage and global crop yield: Looking at the whole spectrum of pollinator dependency Commun Integr Biol.2 37 39 https://doi.org/10.4161/cib.2.1.7425
Gelernter WD, Stowell LJ, Johnson ME & Brown CD. 2017 Documenting trends in land-use characteristics and environmental stewardship programs on US golf courses Crop Forage Turfgrass Manag.3 1 12 https://doi.org/10.2134/cftm2016.10.0066
Gontijo LM, Beers EH & Snyder WE. 2013 Flowers promote aphid suppression in apple orchards Biol Control.66 8 15 https://doi.org/10.1016/j.biocontrol.2013.03.007
Goulson D, Nicholls E, Botías C & Rotheray EL. 2015 Bee declines driven by combined stress from parasites, pesticides, and lack of flowers Science.347 1435 https://doi.org/10.1126/science.1255957
Haaland C, Naisbit RE & Bersier LF. 2011 Sown wildflower strips for insect conservation: A review Insect Conserv Divers.4 60 80 https://doi.org/10.1111/j.1752-4598.2010.00098.x
Kearns CA, Inouye DW & Waser NM. 1998 Endangered mutualisms: The conservation of plant-pollinator interactions Annu Rev Ecol Evol Syst.29 83 112 https://doi.org/10.1146/annurev.ecolsys.29.1.83
Kevan PG & Phillips TP. 2001 The economic impacts of pollinator declines: An approach to assessing the consequences Conserv Ecol.5 8 25
Kleijn D, Winfree R, Bartomeus I, Carvalheiro LG, Henry M, Isaacs R, Klein AM, Kremen C, M’gonigle LK, Rader R & Ricketts TH. 2015 Delivery of crop pollination services is an insufficient argument for wild pollinator conservation Nat Commun.6 1 9 https://doi.org/10.1038/ncomms8414
Kloppenburg DJ & Hall JC. 1990 Efficacy of five different formulations of clopyralid on Cirsium arvense (L.) Scop, and Polygonum convolvulus L Weed Res.30 227 234 https://doi.org/10.111/j.1365-3180.1990.tb01708.x
Korpela EL, Hyvönen T, Lindgren S & Kuussaari M. 2013 Can pollination services, species diversity and conservation be simultaneously promoted by sown wildflower strips on farmland? Agric Ecosyst Environ.179 18 24 https://doi.org/10.1016/j.agee.2013.07.001
Lingenfelter DD & Curran WS. 2007 Effect of glyphosate and several ACCase inhibitor herbicides on wirestem muhly (Muhlenbergia frondosa) control Weed Technol.21 732 738 https://doi.org/10.1614/WT-06-055.1
Love SL, Hutchinson PJ & Price WJ. 2016 Managing weeds during wildflower meadow establishment in the arid Intermountain West: Efficacy of a grass-first strategy for sites with heavy annual weed pressure Native Plants J.17 216 229
McCurdy JD, McElroy JS & Flessner ML. 2013 Differential response of four Trifolium species to common broadleaf herbicides: Implications for mixed grass-legume swards Weed Technol.27 123 128 https://doi.org/10.1614/WT-D-12-00093.1
McIntosh MS. 1983 Analysis of combined experiments 1 Agron J.75 153 155 https://doi.org/10.2134/agronj1983.00021962007500010041x
Meyer RE & Bovey RW. 1991 Response of yankeeweed (Eupatorium compositifolium) and associated pasture plants to herbicides Weed Technol.5 214 217 https://doi.org/10.1017/S0890037X00033558
Nearing MA, Jetten V, Baffaut C, Cerdan O, Couturier A, Hernandez M, Le Bissonnais Y, Nichols MH, Nunes JP, Renschler CS, Souchere V & van Oost K. 2005 Modelling response of soil erosion and runoff to changes in precipitation and cover Catena.61 131 154 https://doi.org/10.1016/j.catena.2005.03.007
Nelson M. 1997 Natural areas USGA Green Sect Rec.November/December 7 11
Olszyk D, Blakeley-Smith M, Pfleeger T, Lee EH & Plocher M. 2013 Effects of low levels of herbicides on prairie species of the Willamette Valley, Oregon Environ Toxicol Chem.32 2542 2551 https://doi.org/10.1002/etc.2331
Potts SG, Biesmeijer JC, Kremen C, Neumann P, Schweiger O & Kunin WE. 2010 Global pollinator declines: Trends, impacts and drivers Trends Ecol Evol.25 345 353 https://doi.org/10.1016/j.tree.2010.01.007
Scott R. 2008 Wildflower landscapes in the urban environment 258 266 Hitchmough J & Finley K Plant user handbook.Blackwell Publishing Oxford, UK
Steffan-Dewenter I, Potts SG & Packer L. 2005 Pollinator diversity and crop pollination services are at risk Trends Ecol Evol.20 651 652 https://doi.org/10.1016/j.tree.2005.09.004
Thomann M, Imbert E, Devaux C & Cheptou PO. 2013 Flowering plants under global pollinator decline Trends Plant Sci.18 353 359 https://doi.org/10.1016/j.tplants.2013.04.002
Tooker JF & Hanks LM. 2000 Flowering plant hosts of adult hymenopteran parasitoids of central Illinois Ann Entomol Soc Am.93 580 588
Vickery J, Carter N & Fuller RJ. 2002 The potential value of managed cereal field margins as foraging habitats for farmland birds in the UK Agric Ecosyst Environ.89 41 52 https://doi.org/10.1016/S0167-8809(01)00317-6
Vickery JA, Feber RE & Fuller RJ. 2009 Arable field margins managed for biodiversity conservation: A review of food resource provision for farmland birds Agric Ecosyst Environ.133 1 13 https://doi.org/10.1016/j.agee.2009.05.012
Wallisdevries MF, Van Swaay CA & Plate CL. 2012 Changes in nectar supply: A possible cause of widespread butterfly decline Curr Zool.58 384 391
Wiese JL, Keren EN & Menalled FD. 2011 Tolerance of native wildflower species to postemergence herbicides Native Plants J.12 31 36
Williams NM, Ward KL, Pope N, Isaacs R, Wilson J, May EA, Ellis J, Daniels J, Pence A, Ullmann K & Peters J. 2015 Native wildflower plantings support wild bee abundance and diversity in agricultural landscapes across the United States Ecol Appl.25 2119 2131 https://doi.org/10.1890/14-1748.1
Winfree R, Aguilar R, Vázquez DP, LeBuhn G & Aizen MA. 2009 A meta-analysis of bees’ responses to anthropogenic disturbance Ecology.90 2068 2076
Wratten SD, Gillespie M, Decourtye A, Mader E & Desneux N. 2012 Pollinator habitat enhancement: Benefits to other ecosystem services Agric Ecosyst Environ.159 112 122 https://doi.org/10.1016/j.agee.2012.06.020
York A & Seagroves R. 2008 Herbicide options for weed management in the North Carolina highway wildflower program (no. FHWA/NC/2006-60) North Carolina Department of Transportation Research and Analysis Group Raleigh, NC, USA
