Annual Bluegrass Control Research Articles

Nonsynthetic herbicides for turfgrass: Assessing frequency of consumer information and regional performance for annual bluegrass (Poa annua L.) control

AbstractAnnual bluegrass (Poa annua L.) poses significant challenges in managed turfgrass systems due to its adaptability and resilience. This study explores publicly available information on and performance of several organic or nonsynthetic herbicides for annual bluegrass control in turfgrass to address this issue. Through a keyword frequency analysis using Google and Google Scholar, the prevalence of organic weed control treatments was examined, revealing a significant association between search engines, key phrases, and weed management types and general dominance of synthetic herbicides despite phrases specifically targeted at organic options. Field assessments were conducted at 20 site years across four US states to evaluate the efficacy of 14 nonsynthetic herbicides for annual bluegrass control while considering turfgrass safety. Results indicate that nonsynthetic herbicides fail to provide long‐lasting control of annual bluegrass when applied once and injure turfgrass. The study highlights the challenges in achieving long‐term control of annual bluegrass, especially with nonsynthetic herbicides, which have limited effectiveness against established weeds. Cost and environmental considerations further complicate the adoption of organic or nonsynthetic weed management programs, despite their perceived environmental benefits. Overall, the research underscores the need for continued exploration of integrated weed management strategies, including targeted application methods, to address the complexities of annual bluegrass control in turfgrass systems.

Evaluation of spring-applied endothall for annual bluegrass control in warm-season turf

Abstract Increasing instances of herbicide-resistant annual bluegrass have limited turf manager’s options for chemical control. Endothall inhibits serine threonine protein phosphatase, a novel site of action for warm-season turf, and endothall use in hybrid bermudagrass is not extensively reported. Greenhouse studies were conducted to evaluate herbicide-resistant annual bluegrass response to endothall. Five herbicide-resistant annual bluegrass biotypes were treated with increasing endothall rates and compared to two susceptible populations. One glyphosate-resistant annual bluegrass biotype was 2.3- to 3.3-fold more resistant to endothall depending on trial and susceptible biotype, and all other biotypes were endothall-susceptible. Four field studies were established from 2022-2023 to evaluate the influence of endothall rate and application timing on bermudagrass and manilagrass turf injury and annual bluegrass control. These studies were arranged as a three-by-four factorial with three levels of application timing (fully dormant, 50% green, and 100% green) and four levels of herbicide (endothall applied at 1.12, 1.68, and 2.24 kg ai ha-1 and trifloxysulfuron applied at 27.8 g ai ha-1). Maximum observed turf injury was dependent on endothall rate and timing and was commercially acceptable (<30%) at the low and middle rates when applied to 100% green bermudagrass and all rates when applied to dormant turf. When applied to 50% green turf (mid-transition), endothall unacceptably injured warm-season turf regardless of application rate, but when applied during mid-transition, only the high endothall rate unacceptably injured turf 14 days after treatment. Endothall controlled annual bluegrass more effectively when applied during mid-transition and 100% green turf than fully dormant turf. When applied at 1.68 and 2.24 kg ai ha-1 to mid-transition and 100% green turf, endothall controlled annual bluegrass 83-95%. Results from these studies indicate endothall selectively controls herbicide-resistant annual bluegrass in warm-season turf but selectivity and performance depend on application timing.

Evaluation of Pyroxasulfone Crop Safety and Weed Control for California Tree Nut Orchards

Pyroxasulfone is a very long chain fatty acid (VLCFA) inhibitor (group 15) with potential for preemergence weed control in orchard crops and would be beneficial for reducing selection pressure for resistance to more commonly used herbicides, such as glyphosate. Pyroxasulfone is registered and widely used in corn and soybeans in the United States as a solo product and in several premix formulations. However, there is limited published information on the performance and safety of pyroxasulfone in tree nut orchard systems. To assess the potential fit for pyroxasulfone in this crop sector, a series of crop safety and weed control efficacy experiments were carried out in key California orchard crops and in fallow fields with common orchard weeds. The non-crop studies were conducted near Davis, CA, to evaluate winter annual weed control with pyroxasulfone in comparison with pendimethalin and indaziflam. In addition, an irrigation incorporation experiment was conducted in summer to evaluate the effects of incorporation timing on pyroxasulfone, pendimethalin, and indaziflam efficacy as a measure of relative stability. Orchard weed control experiments were conducted in spring in an almond orchard near Arbuckle, CA, and a walnut orchard near Davis, CA. The orchard experiments included pyroxasulfone, pendimethalin, and indaziflam in various rate combinations with glufosinate. To evaluate crop safety, 2-year experiments were conducted to evaluate repeated applications of above-label rates of pyroxasulfone at 1199 g·ha−1 and S-metolachlor at 14,010 g·ha−1 on 1- to 2-year-old almond, pistachio, and walnut trees near Davis. Pyroxasulfone performed similarly to commercial standards with up to 95% control of broadleaf and grass weeds with pyroxasulfone and indaziflam providing 96% to 100% control of annual bluegrass, and pyroxasulfone (293 g·ha−1) being the only herbicide to suppress (>70%) common lambsquarters at 60 days after treatment (DAT). Other weeds controlled by pyroxasulfone include swinecress, redroot pigweed, yellow nutsedge, and Italian ryegrass. No differences were found among treatments in the incorporation timing study indicating adequate stability on the soil surface under summer conditions. Crop injury was not observed in the established orchards or the young orchard studies and there were no treatment effects on tree trunk diameter of almond, pistachio, and walnut in the 2-year crop safety experiments. These results indicate a potential for pyroxasulfone in California tree nut orchard systems that would be an additional site of action and beneficial for management of herbicide-resistant weeds in these crops.

Effect of spray droplet spectra on control of Poa annua with pronamide

AbstractAnnual bluegrass is a troublesome weed in turfgrass, with reported resistance to at least 12 herbicide sites of action. The mitotic-inhibiting herbicide pronamide has both preemergence and postemergence activity on susceptible annual bluegrass populations. Previous studies suggest that postemergence activity may be compromised due to lack of root uptake, as well as target-site- and translocation-based mechanisms. Research was conducted to determine the effects of spray droplet spectra on spray coverage and control of annual bluegrass with pronamide, flazasulfuron, and a mixture of pronamide plus flazasulfuron. Herbicides were delivered to annual bluegrass plants having two to three leaves via five different spray spectra based on volume median diameters (VMD) of 200, 400, 600, 800, and 1,000 µm. Fluorescent tracer dye was added to each treatment solution to quantify the effects of herbicide and spray droplet spectra on herbicide deposition. In another experiment, the efficacy of 0.58, 1.16, and 2.32 kg pronamide ha−1; 0.022, 0.044, and 0.088 kg flazasulfuron ha−1, or a combination of the two, were assessed in iteration with droplet spectrum sprays of 400 and 1,000 µm on two pronamide-resistant and two pronamide-susceptible annual bluegrass populations. Spray droplet spectrum affected the deposition of pronamide and flazasulfuron, applied alone and in combination. Pronamide foliar deposition decreased with increasing droplet spectra. Pronamide efficacy was affected by droplet spectrum, with the largest (1,000 µm) exhibiting improved control. Flazasulfuron efficacy and pronamide plus flazasulfuron efficacy were not affected by droplet spectra. Pronamide plus flazasulfuron mixture controlled all four populations more effectively than pronamide alone, regardless of droplet spectra. A mixture of pronamide plus flazasulfuron applied with relatively large droplets may be optimal for annual bluegrass control, which offers valuable insights for optimizing herbicide application and combatting herbicide resistance. However, applications in this controlled-growth pot study may not mimic conditions in which thatch and turfgrass canopy limit the soil deposition of pronamide.

Zoysiagrass and weed response to herbicides during post-dormancy transition

AbstractWinter annual weeds begin to germinate as zoysiagrass enters winter dormancy in autumn. These weeds can suppress zoysiagrass shoot development the following spring through competition for sunlight, moisture, and nutrients. Previous research involving winter annual weed control in dormant turfgrass has been conducted primarily on bermudagrass, but less is known about how various herbicides used for this purpose will influence zoysiagrass after dormancy transition. Two field studies were conducted over 7 site-years between 2016 and 2020 to evaluate 17 herbicide treatments that are typically marketed for broadleaf weed control in spring and 18 herbicide treatments that are typically marketed for annual bluegrass control during winter for their effects on a variety of weeds and semidormant ‘Meyer’ and dormant ‘Zeon’ zoysiagrass, respectively. Glufosinate, glyphosate + simazine, and indaziflam + simazine controlled Persian speedwell by more than 90% and control was significantly greater with auxin-type and other herbicide combinations. Dandelion and Persian speedwell were better controlled with a combination of simazine and glyphosate than when glyphosate was applied alone. Glufosinate controlled dandelion, hairy bittercress, and Persian speedwell more effectively than glyphosate. In Meyer zoysiagrass, glyphosate and glufosinate controlled annual bluegrass equivalently, whereas in Zeon zoysiagrass, glyphosate controlled annual bluegrass better than glufosinate did. Foramsulfuron or treatments that contained simazine resulted in >90% control of annual bluegrass. A flumioxazin admixture with diquat, glufosinate, or glyphosate improved annual bluegrass control. Herbicide treatments that contain diquat, glufosinate, glyphosate, and metsulfuron alone or in a tank-mix should not be applied to Meyer zoysiagrass with 5% visual green turf cover due to high injury potential. In both studies, glufosinate was more injurious to Meyer and Zeon zoysiagrass than glyphosate. Overall, several herbicides that control annual bluegrass or broadleaf weeds can be safely applied to Zeon zoysiagrass during dormancy or Meyer zoysiagrass during post-dormancy transition.

Annual bluegrass weevil (Listronotus maculicollis) and paclobutrazol control annual bluegrass (Poa annua) in creeping bentgrass fairways

AbstractThe annual bluegrass weevil (ABW) is a pest of fine turfgrass, but recent research has found that withholding insecticides for ABW control can reduce annual bluegrass cover. The objective of this research was to evaluate threshold-based insecticide and paclobutrazol programs for annual bluegrass control. The effect of three insecticide programs (preventive, threshold, and no insecticide) and four rates of paclobutrazol (0, 70, 105, or 210 g ha−1 applied monthly) were evaluated. Replicate experiments were conducted from April to November in both 2018 and 2019 on a mixed creeping bentgrass and annual bluegrass fairway in North Brunswick, NJ. By the conclusion of both experiments, all paclobutrazol programs exhibited reduced annual bluegrass cover compared with the nontreated plots. In threshold and no-insecticide programs, reduction in annual bluegrass cover was enhanced by paclobutrazol applied at 105 g ha−1 in both years, and at 70 g ha−1 in the 2019 experiment. Paclobutrazol at 210 g ha−1 resulted in annual bluegrass cover of <20% regardless of insecticide program. In 2019, threshold-based ABW control without paclobutrazol provided similar annual bluegrass control as monthly applications of paclobutrazol at 70 and 105 g ha−1 with the preventive insecticide program. A reduction in turfgrass quality from threshold-based insecticide programs persisted for a shorter duration than the no-insecticide program, regardless of paclobutrazol treatment. Threshold-based ABW insecticide programs that allow ABW feeding damage to occur can result in reduced annual bluegrass cover. These reductions were further enhanced by paclobutrazol applications. The combination of threshold-level insecticide with moderate rates of paclobutrazol (70 to 105 g ha−1) provided reductions in annual bluegrass cover that were similar to the highest rate of paclobutrazol (210 g ha−1) without ABW damage. Turfgrass managers who integrate the threshold-level insecticide approach and monthly paclobutrazol applications may achieve greater annual bluegrass control than either strategy alone if temporary reductions in turf quality can be tolerated.

Mesotrione and Amicarbazone Tank-mixtures for Annual Bluegrass (Poa annua) Control in Cool-season Turfgrass

Annual bluegrass (Poa annua L.) control with postemergence herbicides in cool-season turfgrass is often inconsistent. Amicarbazone and mesotrione have complementary modes of action but have not been evaluated in tank-mixtures for control of mature annual bluegrass in cool-season turfgrass. Field experiments were conducted during 2018 in New Jersey, and in Indiana, Iowa, and New Jersey during 2019 to evaluate springtime applications of amicarbazone and mesotrione for POST annual bluegrass control in cool-season turfgrass. On separate tall fescue (Festuca arundinacea Schreb.) and kentucky bluegrass (Poa pratensis L.) sites in 2018, three sequential applications of amicarbazone (53 g⋅ha−1) + mesotrione at 110 to 175 g⋅ha−1 provided >70% annual bluegrass control, whereas three sequential applications of amicarbazone alone at 53 and 70 as well as two sequential applications at 110 g⋅ha−1 provided <15% control at 14 weeks after initial treatment (WAIT). In 2019, results in New Jersey were similar to 2018 where amicarbazone alone provided less control than mesotrione + amicarbazone tank-mixtures. In Indiana, where the annual bluegrass infestation was severe and most mature, tank-mixtures were more effective than amicarbazone alone at 6 WAIT, but at 12 WAIT all treatments provided poor control. In Iowa, where the annual bluegrass infestation was <1 year old, all treatments provided similar control throughout the experiment and by >80% at the conclusion of the experiment. This research demonstrates that sequential applications of mesotrione + amicarbazone can provide more annual bluegrass control than either herbicide alone, but efficacy is inconsistent across locations, possibly due to annual bluegrass maturity and infestation severity.

Wood vinegar resulting from the pyrolysis of apple tree branches for annual bluegrass control

Wood vinegar resulting from the pyrolysis of apple tree branches for annual bluegrass control

Exploring Natural Alternatives for Annual Bluegrass Control

A field experiment was conducted to identify and examine the effectiveness of potential non-traditional chemical products and alternatives for controlling annual bluegrass (Poa annua L.), a plant with increasing herbicide resistant problems. In managed turf systems annual bluegrass can be a difficult winter annual weed to control having negative impacts on turfgrass quality. This study included 12 different treatments [untreated check, baking soda, white vinegar + lemon juice, Suppress herbicide, superphosphate (0-20-0), clove oil, Weed Zap, Avenger Weed Killer, Fiesta Turf Weed Killer, Ecologic Weed & Grass Killer, Alcohol (43% ethanol), and Pool Time Algicide] applied to a TifEagle bermudagrass (Cynodon dactylon × C. traansvalensis) putting green where a natural infestation of annual bluegrass was present. Treatments were assessed visually for annual bluegrass control and turf phytotoxicity 1, 2, and 4 weeks after application. Overall, no treatment provided long-term control which was non-selective. Control was short-lived with annual bluegrass recovery beginning approximately two weeks after applying treatments. Greatest Poa burndown (~85%) was temporarily (1 to 2 weeks after application) with a combination of caprylic and capric acids (Suppress Herbicide) and a combination of clove oil and dishwashing detergent but plants fully recovered by three weeks after application. These products also produced similar temporary turf phytotoxicity. Bermudagrass turf phytotoxicity from selective treatments was most evident one week after applying treatments and turf had mostly fully recovered by four weeks after treatment. Suitable alternatives were not identified from products tested.

Non-Chemical Control of Annual Bluegrass (Poa annua) in Bermudagrass (Cynodon spp.) via Fraise Mowing: Efficacy and Barriers to Adoption

Fraise mowing is a maintenance practice that may serve as a non-chemical means of controlling the problematic weed annual bluegrass (Poa annua L.) in bermudagrass (Cynodon spp.) given reports of efficacy on other turfgrass species. However, an understanding of practitioner decision-making in implementing fraise mowing as a weed-control measure remains unknown. A field study was conducted in Knoxville, TN and repeated in space in Jay, FL during summer 2019 to assess bermudagrass regrowth and subsequent annual bluegrass control, following fraise mowing at depths of 1.5 and 3.0 cm compared to a non-treated check (0 cm). Bermudagrass recovered more quickly at the 1.5 cm depth than the 3.0 cm depth and was the swiftest in Florida. Fraise mowing at either depth resulted in a 41–97% reduction in annual bluegrass populations. A qualitative study was conducted in spring 2021, which engaged eight turfgrass managers from Tennessee and Florida via individual interviews in order to understand barriers and challenges to fraise mowing application. Turfgrass managers had positive views of fraise mowing but described challenges in implementation for weed control including cost, labor, area closure, and debris removal.

Suppression of Annual Bluegrass in Creeping Bentgrass Putting Greens Using Plant Growth Regulators

Decreased stand uniformity together with reduced aesthetics and playability caused by annual bluegrass (Poa annua) intrusion in creeping bentgrass (Agrostis stolonifera) putting greens is one of the major problems that golf course superintendents face with managing newer playing surfaces. Few herbicides are registered for selective control of annual bluegrass in creeping bentgrass greens, and the risk of herbicide resistance remains an issue, thus use of plant growth regulators (PGRs) is still the primary method of annual bluegrass suppression. This study was conducted to evaluate eight PGR treatments, employed as a series of 15 consecutive, biweekly applications to suppress annual bluegrass encroachment in ‘Pure Distinction’ creeping bentgrass maintained as a golf course putting green in Los Angeles, CA. Best annual bluegrass suppression was observed with products containing flurprimidol (FP) at 0.256 lb/acre, paclobutrazol (PB) at 0.119 lb/acre, or three-way mixture of FP, trinexapac-ethyl (TE), and PB (FP+PB+TE) at 0.055, 0.014, and 0.055 lb/acre, respectively. Although all treatments caused some significant creeping bentgrass injury, which increased over time, PB at 0.119 lb/acre and FP+PB+TE at 0.055, 0.014, and 0.055 lb/acre, respectively, appeared to be safest among effective treatments. Additionally, those treatments caused significantly darker green turf, which may be desirable on putting greens. This research confirms the potential of PGR use to limit annual bluegrass infestation on creeping bentgrass greens in a Mediterranean climate and reveals the most effective treatments that could be used in a putting green maintenance program.

Annual bluegrass weevil, paclobutrazol, and overseeding for annual bluegrass control in cool‐season turfgrass

AbstractThe annual bluegrass weevil (ABW; Listronotus maculicollis Kirby) host preference for annual bluegrass (Poa annua L.) is well documented, but ABW efficacy for annual bluegrass control in mixed turfgrass stands has not been researched. This study evaluated threshold‐based insecticide ABW control for annual bluegrass control in mixed‐species golf course fairway turfgrass. To investigate integrated pest management programs for annual bluegrass control in fairways, the effects of creeping bentgrass (Agrostis stolonifera L.) overseeding, three insecticide programs (preventative, threshold‐based, and no insecticide), and the plant growth regulator paclobutrazol (280 g ha–1, applied monthly) were evaluated for annual bluegrass control in field experiments conducted over 2 yr on golf fairways in North Brunswick and Bloomfield, NJ. Treatments were replicated four times and arranged in a split‐split‐plot randomized block design. Overseeding (whole‐plot factor) did not affect annual bluegrass cover at either location. Paclobutrazol (split‐plot factor) reduced annual bluegrass cover each year at both locations. At the North Brunswick site, paclobutrazol resulted in 0% annual bluegrass cover, compared with 37% in the nontreated control at the conclusion of the 2‐yr experiment. Insecticide program (split‐split‐plot factor) only affected annual bluegrass cover at the North Brunswick site. In the absence of paclobutrazol, the no insecticide program had lower annual bluegrass cover (23%) than the threshold (37%) and preventative (44%) programs at the conclusion of the experiment. These findings show that monthly paclobutrazol applications during the growing season can reduce or eliminate annual bluegrass after 2 yr. This is the first study to show that omitting ABW insecticidal control can also reduce annual bluegrass, although efficacy was site specific.

Herbicide symptomology and the mechanism of action of methiozolin

AbstractMethiozolin is a new herbicide with an unknown mechanism of action (MOA) for control of annual bluegrass (Poa annua L.) in several warm- and cool-season turfgrasses. In the literature, methiozolin was proposed to be a pigment inhibitor via inhibition of tyrosine aminotransferases (TATs) or a cellulose biosynthesis inhibitor (CBI). Here, exploratory research was conducted to characterize the herbicide symptomology and MOA of methiozolin. Arabidopsis (Arabidopsis thaliana L.) and P. annua exhibited a similar level of susceptibility to methiozolin, and arrest of meristematic growth was the most characteristic symptomology. For example, methiozolin inhibited A. thaliana root growth (GR50 8 nM) and shoot emergence (GR80 ˜50 nM), and apical meristem growth was completely arrested at rates greater than 500 nM. We concluded that methiozolin was neither a TAT nor a CBI inhibitor. Methiozolin had a minor effect on chlorophyll and alpha-tocopherol content in treated seedlings (<500 nM), and supplements in the proposed TAT pathway could not lessen phytotoxicity. Examination of microscopic images of roots revealed that methiozolin-treated (100 nM) and untreated seedlings had similar root cell lengths. Thus, methiozolin inhibits cell proliferation and not elongation from meristematic tissue. Subsequently, we suspected methiozolin was an inhibitor of the mevalonic acid (MVA) pathway, because its herbicidal symptomologies were nearly indistinguishable from those caused by lovastatin. However, methiozolin did not inhibit phytosterol production, and MVA pathway metabolites did not rescue treated seedlings. Further experiments showed that methiozolin produced a physiological profile very similar to cinmethylin across a number of assays, a known inhibitor of fatty-acid synthesis through inhibition of thioesterases (FATs). Experiments with lesser duckweed (Lemna aequinoctialis Welw.; syn. Lemna paucicostata Hegelm.) showed that methiozolin also reduced fatty-acid content in Lemna with a profile similar, but not identical, to cinmethylin. However, there was no difference in fatty-acid content between treated (1 µM) and untreated A. thaliana seedlings. Methiozolin also bound to both A, thaliana and L. aequinoctialis FATs in vitro. Modeling suggested that methiozolin and cinmethylin have comparable and overlapping FAT binding sites. While there was a discrepancy in the effect of methiozolin on fatty-acid content between L. aequinoctialis and A. thaliana, the overall evidence indicates that methiozolin is a FAT inhibitor and acts in a similar manner as cinmethylin.

Fairway Renovation with Fraise Mowing Cultivation and Dazomet Fumigation

Renovation is an opportune time for golf courses to address annual bluegrass (Poa annua L.) weed populations. Dazomet (tetrahydro-3,5-dimethyl-2H-1,3,5-thiadiazine-2-thione) is an effective fumigant, but without a tarp cover, it is only effective at the highest labeled rates. Fraise mowing cultivation could be used to help remove surface material and allow practitioners to effectively fumigate at lower rates. In Summer 2018 and Summer 2019, two cool-season fairway renovation experiments were conducted in East Lansing, MI. The objective of these experiments was to assess annual bluegrass control and creeping bentgrass establishment following dazomet applications to fraise mowed surfaces. In the first experiment (fraise mowing surface disturbance experiment), dazomet was applied at a fixed rate (294 kg·ha−1) to fraise mowed plots at varying levels of surface disturbance (0%, 15%, 50%, and 100%) to a depth of 1.9 cm. In the second experiment (dazomet rate experiment), fraise mowing removed 100% of surface material at a depth of 1.9 cm and dazomet was applied at five rates (0, 294, 588, 147 + 147, and 294 + 294 kg·ha−1). Both experiments were conducted on two soils (sand topdressed vs. native) and evaluated two methods of fumigant incorporation (solid-tine cultivation vs. tillage). Five days after treatments were applied, plots were seeded with ‘Pure Select’ creeping bentgrass (Agrostis stolonifera L.). The level of fraise mowing surface disturbance had no effect on annual bluegrass emergence, and creeping bentgrass cover was poorest in native soils at the highest levels of surface disturbance. In the dazomet rate experiment, dazomet applied twice at 294 kg·ha−1 provided the most consistent control of annual bluegrass. With the exception to single applications of 294 in 2018, all dazomet treatments allowed for greater creeping bentgrass establishment than the nontreated control. Fraise mowing cultivation may simplify the removal of surface material from large areas; however, even when combined with dazomet applied at the highest rates, it fails to provide complete annual bluegrass control.

Adding a late fall application of Proxy (ethephon) before two traditional spring applications improves seedhead control of annual bluegrass

AbstractAnnual bluegrass (ABG) (Poa annua L.) is a prolific seed producer in the spring on golf courses that in turn decreases aesthetic quality and trueness of ball roll on cool‐season putting greens. Proxy (ethephon) applied twice in the spring after green‐up is the current industry standard after the loss of Embark (mefluidide) from the turf and ornamental market. However, plant growth regulators including Proxy have been used for years to help suppress ABG seedheads with inconsistent success. The primary objective of this study was to determine if ABG seedhead suppression is improved by adding a late fall application of Proxy to the two traditional spring applications of plant growth regulators at nine locations with diverse environments. A second objective was to determine the importance of including Primo Maxx (trinexapac‐ethyl) in fall and spring applications. Adding a late fall application of Proxy prior to the two spring applications (F+S+S) improved control of ABG seedheads over the traditional two spring applications (S+S), but the magnitude of improvement varied among locations. When treatments were applied F+S+S, the industry standard tank mixture of Proxy + Primo Maxx provided consistent ABG seedhead control and turf quality, similar to Proxy + Fiata (phosphonate + proprietary pigment) and equal to or better than Proxy alone.

Phytotoxicity of Methiozolin on Fine Fescue

Methiozolin is a new herbicide that controls annual bluegrass (Poa annua) in turfgrasses, but the differential tolerance levels of fine fescues (Festuca sp.) has received limited investigation. The objective of this study was to investigate the potential injury from methiozolin when applied to chewings fescue (Festuca rubra ssp. fallax), strong creeping red fescue (Festuca rubra ssp. rubra), and hard fescue (Festuca brevipila). Nine different fine fescue populations (14W2 Comp, Fairmont, and Survivor chewings fescue; FT345, Miser, and Fenway strong creeping red fescue; and 14H4 Comp, Stonehenge, and Oxford hard fescue) were sprayed with methiozolin at five different rates (0.42, 0.83, 1.25, 1.67, and 2.09 lb/acre) at four different application timings [4 weeks before seeding (WBS), 2 WBS, at seeding (AS), and 2 weeks after germination (WAG)]. Untreated controls were also included for each combination. Significant reduction in germination of fine fescue was observed when methiozolin was applied before emergence for all tested application rates. Methiozolin at 1.25, 1.67, and 2.09 lb/acre applied before or at the day of seeding led to complete inhibition of germination in all fine fescue species tested. It was less injurious compared with methiozolin applied at 2 WAG, although a reduction in the percentage of green cover and biomass was observed for application rates greater or equal to 0.83 lb/acre. The hierarchical ranking of species injury from high to low is as follows: hard fescue, chewings fescue, and strong creeping red fescue. A possible solution for annual bluegrass control in fine fescue species with methiozolin is multiple postemergence applications up to a maximum rate of 0.83 lb/acre. Turf managers need to make adjustments in methiozolin application rates and timings based on fine fescue species to maximize selectivity for annual bluegrass control.

Long-Term Efficacy of Annual Bluegrass Control Strategies on Golf Course Putting Greens

Long-Term Efficacy of Annual Bluegrass Control Strategies on Golf Course Putting Greens

Evaluating the Efficacy of Dazomet for the Control of Annual Bluegrass Seed Germination in Renovated Turf Surfaces

The soil sterilant, dazomet, is the primary product in the turfgrass industry set to take the position of methyl bromide, which is no longer available for use on turfgrass. With turf surface renovations taking place throughout the country, the need for an effective soil sterilant is critical. This study focused on the ability of dazomet to inhibit germination of annual bluegrass (Poa annua) seeds when it is used as per the current, turf focused, label which decreased legal application rates across all surfaces. This study was a four-way factorial in a split-split plot design with whole plots in a randomized complete block design arrangement with three replications. The first factor, soil type, included two levels. Soil-type plots (60 × 95 ft) were either sand capped from topdressing over the native Capac loam or they were the native Capac loam. Sand topdressing was applied biweekly at a rate of 0.14 yard3/1000 ft2, April to September since 2011; accumulating a total of 1.5 inches of sand. Each of three replicated blocks consisted of two soil-type plots. The second factor was time trials, with two levels of starting times, June and August. Each soil-type plot was split into two subplots and the trials were assigned at random to subplots within each plot. The third factor, soil preparation, involved either removing the upper 1.5 inches of the sod/soil layer or spraying plots with glyphosate and then heavily cultivating them. This cultivation included a vertical-cut and a core cultivation with an aerator using 0.5-inch hollow tines at 2 × 2-inch spacing. The fourth factor, treatment regime, comprised 11 parameters that encompassed dazomet application rate, incorporation method, and the technique used to seal the soil surface. Dazomet treatments were applied with a shaker bottle, at rates that included 262, 421, 525, and 262 lb/acre applied twice at a 5-day interval. The treatments were incorporated into the soil either through 1 inch of irrigation, through four consecutive days of irrigation following this schedule: 1, 0.5, 0.25, 0.125 inch each day after application, respectively, or physically (P) with a rotary tiller set to 1.5 inches, the depth of the topdressing layer. All P incorporated plots were hand rolled following application, regardless of the tarping procedure. Water-incorporated plots were either sealed with a clear plastic 4-mil tarp or they were left unsealed. Researchers evaluated the level of germination control by counting individual annual bluegrass seedlings using a 1 × 1-ft grid. A significant interaction occurred between soil type and soil preparation as well as between soil type and treatment. A three-way interaction also occurred between trial, treatment and soil preparation. In general, tarped treatments showed better annual bluegrass control compared with nontarped treatments. Furthermore, sand topdressed soils showed lower numbers of annual bluegrass as compared with native soils. Finally, reduced annual bluegrass germination was found in plots that had the top 1.5 inches of material removed.

Playing quality, growth rate, thatch accumulation and tolerance to moss and annual bluegrass invasion as influenced by irrigation strategies on red fescue putting greens

AbstractConversion from annual bluegrass or bentgrasses to red fescue could be an efficient way to minimise water use on golf greens. Our objective was to investigate the influences of four irrigation strategies on red fescue water use efficiency, turf quality, growth rate and resistance to annual bluegrass and moss invasion. The trial was carried out from August 2013 to August 2015 on a green established according to USGA recommendations under a rainout shelter at Landvik, Norway (58 °N). On average for 2 years, irrigation to field capacity once per week (FC 1) and deficit irrigation to 60% of FC three times per week (DEF 3) reduced the water consumption by 49% and 72% relative to irrigation to FC three times per week (FC 3). Both DEF 3 and FC 1 retained acceptable turf quality and reduced annual bluegrass in the second year by about one‐third. Better control of annual bluegrass was obtained with deficit irrigation to 60% of FC once per week (DEF 1), but this treatment did not produce acceptable turf quality. Compared with FC 3, DEF 3, FC 1 and DEF 1 gave harder surfaces and reduced the moss invasion in the second year by 66%, 90% and 93%, respectively. Irrigation effects on root development and thatch organic matter after 2 years were not significant, although the thatch layer depth was 3–4 mm greater in FC 1 than in the other treatments. In conclusion, DEF 3 and FC 1 are both effective irrigation strategies for managing red fescue greens with less water use.

Annual Bluegrass Control during Hybrid Bluegrass Establishment from Sprigs

Hybrid bluegrass (Poa arachnifera Torr. × P. pratensis L.) establishment may be compromised by the emergence of annual bluegrass (P. annua L.) in the fall. The objective of this research was to evaluate the efficacy of herbicides for annual bluegrass control during the establishment of ‘DALBG 1201’ hybrid bluegrass from sprigs. Herbicides were applied at two timings: 5 d after planting (DAP) or 3 wk after planting (WAP). Hybrid bluegrass cover was rated four times between 9 and 35 WAP. The first and second visual ratings of annual bluegrass cover were made between 16 and 18 and at 30 WAP, respectively. At 26 WAP, hybrid bluegrass cover was approximately two‐fold in plots treated with mesotrione, oxadiazon, or topramezone compared with the nontreated. Primisulfuron applied singly or sequentially at 0.04 kg ha−1 controlled annual bluegrass ≥88% but reduced hybrid bluegrass cover >30% relative to the nontreated. Ethofumesate applied at 0.84 kg ha−1 at 3 WAP controlled annual bluegrass 74%. Oxadiazon at 1.12 or 2.24 kg ha−1 applied 5 DAP controlled annual bluegrass 67 to 75% at 30 WAP without reducing hybrid bluegrass cover. All other treatments provided poor (<70%) control of annual bluegrass. Overall, hybrid bluegrass was tolerant to ethofumesate, oxadiazon, mesotrione, and topramezone at rates evaluated during establishment from sprigs. Programs that included ethofumesate at 0.84 kg a.i. ha−1 or oxadiazon at 1.12 or 2.24 kg ha−1 provided best annual bluegrass control and improved hybrid bluegrass cover from the nontreated.