Epichloë spp. grow symbiotically within cool-season grasses and can provide crop protection against pests and drought stress. Winter cutworm (Noctua pronuba L.) is a serious insect pest of cool-season turfgrass and grass seed crops in Oregon (United States). In 2023, we conducted 2 greenhouse experiments to measure the effect of Epichloë infection in 8 cultivars of tall fescue (Schedonorus arundinaceus (Schreb.) Dumort) and perennial ryegrass (Lolium perenne L.) on N. pronuba mortality, weight gain, grass biomass, and feeding damage at 3 time points. Epichloë infection in grass plants was molecularly validated postexperiment. We did not observe an effect of Epichloë infection level or grass cultivar on N. pronuba, regardless of grass species in trial 1. In trial 2, Epichloë infection level effects remained minimal, while cultivar affected feeding damage at 3 and 12 d in both grass species. Feeding damage at 15 d did not vary among cultivars in both tall fescue and perennial ryegrass due to continuous and severe defoliation by N. pronuba. Insect mortality and weight gain were different among tall fescue cultivars. However, some cultivars were forage type, which was selected to be palatable to grazing animals, and could be preferred by the larvae. The perennial ryegrass cultivars were all turf-type and showed no variability in insect responses. The observed feeding damage variations were likely associated with cultivar-specific traits rather than Epichloë infection levels. Understanding the role of grass genotype in grass-Epichloë symbioses is critical to develop practical management for N. pronuba, and other cutworm species.

Plant-parasitic nematodes (PPNs) are important pests affecting golf course putting green health, playability, and management. Recently, they have become a concern for golf course superintendents managing cool-season grasses in the Pacific Northwest (PNW) as reports of damage attributable to PPN activity have increased. Minimal information is available on the species identity and PPN distribution across the region. In November of 2023, soil samples were collected from 264 golf course putting greens in Washington, Oregon, and California for PPN extraction and identification. Meloidogyne spp. (root-knot nematode) was one of the most encountered PPN, occurring in 89% of samples, with maximum PPN densities exceeding 10,000 second stage juveniles 100 cc −1 . In OR and CA samples Meloidogyne minor and Meloidogyne naasi was documented, while only M. naasi was documented in WA. These findings will help inform future efforts into the development of regional damage thresholds, and into appropriate management strategies for PNW cool-season golf courses.

Dollar spot of annual bluegrass ( Poa annua), caused by Clarireedia jacksonii, has never been formally reported in Oregon. This pathogen is one of the most important turfgrass diseases of cool-season grasses worldwide. In 2023, C. jacksonii was detected on an annual bluegrass putting green in Corvallis, OR. This report details the identification efforts and the pathogenicity testing of the recovered isolate on annual bluegrass, creeping bentgrass, perennial ryegrass, and tall fescue. The confirmation of C. jacksonii in Oregon may have management implications for golf course superintendents of the state.

Poa annua L. is one of the most widespread and troublesome weeds of turfgrass. It persists as both an annual and perennial and is adaptable to almost any static maintenance regime, including adaptation to mowing heights and evolution of herbicide resistance. This management guide is intended to provide stakeholders with a summary of new and existing knowledge on integrated Poa annua management. Here we review the basic biology and ecology, as well as practical integrated weed management (IWM) strategies developed for its control.

The Pacific shoot-gall nematode (Anguina pacificae) is an economically important pest of annual bluegrass (Poa annua L.) putting greens in the coastal areas of northern and central California. In December 2024, diagnostic samples submitted to the Oregon State University Turfgrass Diagnostic Clinic (Corvallis, OR) from a golf course tee box in Clark County, Washington contained A. pacificae. Visual symptoms of chlorotic patches and dieback of the turf surface were observed, as well as swellings in the crowns that contained second-stage juveniles (J2). Morphological features as well as morphometric measurements of J2 were consistent with A. pacificae. Sequencing of the internal transcribed spacer (ITS) and the mitochondrially encoded cytochrome c oxidase I (COX1) gene regions confirmed the species identity. To our knowledge, this is the first report of A. pacificae parasitizing turfgrass in Washington.

Plant-parasitic nematodes (PPN) are important pests affecting golf course putting greens. Recently, PPN have become a pest of concern in the Pacific Northwest (PNW), but relatively little information exists on the species present or their distribution across the region. A survey and community analysis of PPN across five independently managed golf courses in Southwest Oregon was conducted. In 2023, soil samples were collected from 30 putting greens in January, May, August, and November. Nematodes were extracted using Baermann funnel and mist extraction methods and identified using morphological and molecular methods. PPN community diversity measures were assessed. Permutational multivariate analysis of variance testing indicated significant differences in PPN communities among season, course, and extraction method. Helicotylenchus and Meloidogyne were the most frequently encountered PPN, with maximum population densities of 20,776 and 59,100 nematodes per 100 cm3 soil, respectively. Indicator species analysis revealed Meloidogyne as a PPN of concern at three of the courses, particularly in January when population densities were highest just prior to reported damage. Representative populations from each course were collected for speciation. Two PPN species were identified at all courses, Helicotylenchus pseudorobustus and Meloidogyne naasi, whereas other species were found to be course specific. An unidentified species of Heterodera was recovered from mixed stand putting greens. This is the first survey of golf course putting green PPN communities across multiple seasons in the PNW. With an increase in damage symptoms reported in this region, there is a need for further assessment of PPN impacts on PNW golf courses.

Hard fescue ( Festuca brevipila ) is a fine‐leaved cool‐season turfgrass and is well adapted for low‐maintenance areas, such as home lawns, parks, and roadsides. Breeding for improved disease resistance is a major objective in utilizing hard fescue under low‐input management. The Epichlöe festucae endophyte‐mediated dollar spot ( Clarireedia jacksonii ) resistance and its mechanism have been well‐documented in strong creeping red fescue ( F. rubra subsp. rubra ). However, little is known about dollar spot resistance in hard fescue. The objectives of this research were to (1) understand the inheritance of dollar spot resistance in hard fescue and determine the reciprocal effects by performing a diallel cross between three resistant endophyte‐containing and three susceptible endophyte‐free parents and (2) confirm the role of E. festucae endophyte in dollar spot resistance by artificially inoculating hard fescue with the endophyte (ME+) and comparing ME+ plants to their genetically identical counterparts without the endophyte (E‒) under dollar spot pressure. The highly significant maternal effect from the diallel cross experiment demonstrated that the dollar disease resistance is maternally inherited in hard fescue and linked with the maternal inheritance of the E. festucae endophyte. The greenhouse study further confirmed that the presence of E. festucae endophyte significantly reduced dollar spot in hard fescue. Understanding this endophyte effect on maternal inheritance of dollar spot resistance will enable more efficient breeding and selection of plant materials to use in the development of improved dollar spot resistant cultivars in hard fescue.

Drought tolerance in turfgrass species and optimal irrigation strategies are key to addressing the need for water conservation in our landscapes. Preliminary findings on tall fescue [ Schedonorus arundinacea (Schreb.) Dumort., nom. Cons] in western Oregon have determined that this species can persist at a high-quality level with very little evapotranspiration (ET) replacement. Research on perennial ryegrass ( Lolium perenne L.) in western Oregon has suggested deficit ET replacement is also a viable weed management tool. Considering these preliminary findings, the objectives of this research were to evaluate the effects of reference evapotranspiration (ET ref ) replacement levels, irrigation intervals, and a no irrigation control treatment on tall fescue appearance and weed encroachment. This research was conducted in western Oregon on a silty clay loam soil. Factors in this experiment included two irrigation frequencies (once or four times a week) and two ET ref replacement rates (45% and 80%) compared to a control treatment (no irrigation). The 80% ET ref replacement rate resulted in the greatest turf color, followed closely by the 45% ET ref replacement treatment. The no irrigation control treatment was able to sustain acceptable turfgrass color for most of the year, with the exception during the month of August. Tall fescue will remain visually acceptable when soil volumetric water content is maintained around 15% or greater in a silty clay loam. The no irrigation control treatment also produced substantial reductions in weed populations (annual and perennial broadleaf weeds and annual grasses).

Municipalities are considering alternatives to traditional herbicides for suppressing weeds and vegetation in areas frequented by the public. Two field experiments were conducted to test the efficacy of alternative nonselective herbicides: one in Corvallis, OR, on a mixed lawn of perennial ryegrass, annual bluegrass, and broadleaf weeds, and another in Las Cruces, NM, on a predominantly bermudagrass lawn with broadleaf weeds. The experimental objective was to quantify and compare the effects of repeated applications of 10 nonselective herbicides to terminate a lawn with mixed vegetation. Applications were made every 2 wk for four applications starting on April 15, 2022, in Corvallis and on May 26, 2022, in Las Cruces. Data collected included the percent green cover over time calculated using an area under the percent green cover progress curve (AUPGCPC), the percent green cover at the conclusion of the experiment, and the changes in monocot and dicot densities over the course of the experiment. All treatments resulted in a lower AUPGCPC compared to water only, except for mint oil + sodium lauryl sulfate + potassium sorbate. The only treatments with average percent green cover <50% were ammoniated soap of fatty acids + maleic hydrazide (47% green cover) in Corvallis and pelargonic acid (38%) in Las Cruces, suggesting that more applications would be needed to terminate the lawn under similar circumstances. At the conclusion of the experiment, the water-only plots averaged 90% and 93% green cover in Corvallis and Las Cruces, respectively. The changes in monocot and dicot densities over the course of the experiment indicated that some of the products tested may be more sensitive to dicots, or, in some cases, monocots, suggesting a potential for future selective herbicide research in certain locations and climates.

Plain Language SummaryPoa annua is a troublesome weed in turfgrass areas such as golf courses, athletic fields, lawns, and sod farms. Controlling P. annua is made more difficult by the growing problem of herbicide resistance, the inherited ability of plants to survive herbicide applications that would normally be lethal. Researchers from 13 academic institutions collected 866 P. annua populations from different states and turfgrass systems to better understand the extent of this problem. Collections were divided and treated with four herbicides and one plant growth regulator. Plants were categorized as “susceptible” or “suspected resistant” based on their response to treatments. Suspected resistance (to at least one or more treatments) was observed in 16.8% of P. annua collections. Herbicide resistance in P. annua is a problem spanning different geographies and management practices. Therefore, coordinated research is needed to explore the scope and nature of the problem in a systematic way.

Annual bluegrass (Poa annua L.) is the most troublesome weed on golf courses in the US. Many agronomic practices intended to promote high-quality playing surfaces favor the growth and development of annual bluegrass, resulting in high weed pressure. One commonly used herbicide for annual bluegrass control on golf courses is ethofumesate, which is a very long chain fatty acid inhibitor. Annual bluegrass resistance to this herbicide is documented and confirmed in grass seed production systems, but potential resistance on golf courses was previously unknown. The objective of this study was to determine the frequency and magnitude of potential ethofumesate resistance from a sample of US golf courses. A dose-response experiment was initiated at Purdue University using 30 annual bluegrass populations collected from Alabama, California, Indiana, and Oregon golf courses. Ten ethofumesate doses included 0, 0.5, 1.0, 2.5, 5.0, 7.5, 10.0, 15.0, 20.0, and 40.0 lb a.i. acre(-1), with 1.0 to 2.0 a.i. acre-1 as the standard label application rate for perennial ryegrass turf. A low level of resistance (R/S < 3) was found in several populations collected in each state. The mean effective dose necessary to kill 50% of the populations (ED50) was 5.1, 9.2, 3.5, and 3.4 lb a.i. acre(-1) for populations from Alabama, California, Indiana, and Oregon, respectively. The most resistant population originated from California, with an ED50 of 13.2 lb a.i. acre(-1). To reduce selection pressure from ethofumesate populations, golf course superintendents are encouraged to develop site-specific weed control programs that rotate herbicide sites of action, as well as utilize diverse control tactics.

The western portion of the Pacific Northwest is known for being dry in the summer and cool and humid in the other months. Tall fescue is valued for its drought and heat tolerance, making it a desirable choice in regions where water is scarce and often restricted by legislation during periods of drought in the summer. However, cool and humid climates make it challenging to manage tall fescue in the winter because unacceptable quality is often observed due to low-temperature diseases and thinning in turf. A field trial was initiated in Autumn 2020 in Corvallis, OR, USA to assess the effects of mowing height as well as fertility timing and rate on tall fescue performance. Two mowing heights of 5.1 and 7.6 cm, four seasonal fertility timings, and three levels of annual N rates of 98, 196, and 294 kg·ha −1 ·yr −1 were evaluated using a 2 × 4 × 3 factorial experiment in a strip-plot design. Quantitative data of percent green cover and normalized difference vegetation index (NDVI) suggest that autumn fertilization is needed in cool, humid areas where tall fescue is actively growing in the winter months. The annual fertilization rate of 294 kg·ha −1 ·yr −1 N produced higher green turf cover and NDVI, compared with 98 or 196 kg·ha −1 ·yr −1 N. Furthermore, divergent effects of mowing heights were observed during winter compared with other months, suggesting that tall fescue could be mowed lower at 5.1 cm during cool, humid winter months and higher at 7.6 cm in other seasons for better overall turfgrass growth and less winter disease and thinning. Our research provides practical cultural practices for managing tall fescue turf in the Pacific Northwest or similar climates.

Fresh water is a scarce resource that needs to be conserved. Landscape irrigation, a large portion of the outdoor water use, can be accomplished with water of less-than-potable quality. The use of effluent water generated from residential graywater in landscapes would go a long way toward conserving potable water for other essential uses. The objectives of this study were to evaluate the effect of effluent versus fresh water irrigation on the performance of 11 lawn-height perennial ryegrass ( Lolium perenne L.) cultivars in the Willamette Valley of Oregon, USA, and determine the effects of effluent water irrigation on soil and tissue analyses. A two-year field trial was established in October 2015 on native soil, and the experimental design was an 11 by 2 strip-plot design with three replications. Synthetic effluent water (water-softening salt, two laundry detergents, and a chelating agent) was applied twice-weekly over perennial ryegrass plots in the summers of 2016 and 2017 and compared to a freshwater control. Small reductions in turf color and density were observed with effluent water irrigation only in June and July of 2017. Our results suggest that effluent water is a viable alternative to freshwater irrigation in the Willamette Valley, where there is little to no precipitation during summer. However, the accumulation of Na, Cl, and B in the soil and plant tissue indicates that future research is warranted to determine any long-term effects from effluent water irrigation on turfgrass and soil health.

Controlling unwanted annual bluegrass ( Poa annua L.) in desirable turfgrass species often relies heavily on herbicide use. As a result, increasing populations of herbicide-resistant annual bluegrass have become a concern. In 2018, a university research and extension initiative began addressing the increasing herbicide-resistant annual bluegrass epidemic. Preliminary findings produced by this research initiative were presented to golf course employees at the 2022 Golf Course Superintendents Association of American Educational Conference in San Diego, California. Findings were presented by a panel of scientists working on various annual bluegrass research sub-objectives. A survey was designed to match the sub-objectives within this panel presentation and determine what recommendations the attendees were most likely to use. The survey also identified environmental zones where participants originated and what turfgrass species they are managing in various areas of the golf course. The goal of sharing these survey findings is to assist turfgrass extension specialists and managers interested in designing annual bluegrass management programs that match stakeholder needs. Survey results determined that extension material pertaining to controlling annual bluegrass with cultural practices would interest the largest stakeholder cross section regardless of environmental turfgrass zone. Another major topic was annual bluegrass emergence patterns for herbicide timing, which was the most important or interesting topic for golf course employees in the warm-season turfgrass environmental zone.

The prolific seed production and polyploidy of annual bluegrass allow for the rapid development of herbicide resistance. Ethofumesate-resistant annual bluegrass plants were identified in the 1990s in grass seed production in Oregon, but their prevalence and distribution are not well documented. Therefore a dose-response experiment was initiated to determine the potential level of ethofumesate resistance in seed production systems. Seeds from 55 annual bluegrass populations were obtained from three sources: seed production fields (31 populations), the seed cleaning process (6 populations), and seed testing lots prior to retail distribution (18 populations). Additionally, two populations, one with known ethofumesate resistance and one with known susceptibility, were identified in preliminary testing and used as controls in this experiment. Seed from each collected population was increased. Individual seedlings were then transplanted into separate cone-tainers, grown to a size of 2 to 3 tillers in the greenhouse, and then sprayed using a compressed air track spray chamber with 10 doses of ethofumesate at 0, 0.56, 1.1, 2.8, 5.6, 8.4, 11.2, 16.8, 22.4, and 44.8 kg ai ha(-1), with 0.84 to 2.2 kg ha(-1 )as the label application rate for perennial ryegrass. The resistant to susceptible ratio of populations across all sources ranged from 0.5 to 5.5. The most resistant populations found in production fields, seed cleaning, and seed testing lots had the effective dose necessary to kill 50% of the population (ED50) of 12.1, 9.4, and 13.1 kg ha-1, respectively. Furthermore, 68% of the populations found in production fields had ED50 higher than 6 kg ha-1, indicating common annual bluegrass resistance in grass seed production. As such, growers should implement integrated weed management strategies, as herbicides alone will likely be ineffective at controlling annual bluegrass.

Gray leaf spot of perennial ryegrass ( Lolium perenne), caused by Pyricularia oryzae, is a devastating turfgrass disease in many regions of the United States. In 2021, P. oryzae was detected for the first time in Oregon, causing disease on a perennial ryegrass athletic field. This report describes the occurrence of gray leaf spot and pathogenicity testing on the original infected cultivar mixture. The confirmation of this pathogen in Oregon could have management implications for turfgrass managers of the state.

This study quantifies golf course pesticide risk in five regions across the US (Florida, East Texas, Northwest, Midwest, and Northeast) and three countries in Europe (UK, Denmark, and Norway) with the objective of determining how pesticide risk on golf courses varied as a function of climate, regulatory environment, and facility-level economic factors. The hazard quotient model was used to estimate acute pesticide risk to mammals specifically. Data from 68 golf courses are included in the study, with a minimum of at least five golf courses in each region. Though the dataset is small, it is representative of the population at confidence level of 75 % with a 15 % margin of error. Pesticide risk appeared to be similar across US regions with varied climates, and significantly lower in the UK, and lowest in Norway and Denmark. In the Southern US (East Texas and Florida), greens contribute most to total pesticide risk while in nearly all other regions fairways make the greatest contribution to overall pesticide risk. The relationship between facility-level economic factors such as maintenance budget was limited in most regions of the study, except in the Northern US (Midwest, Northwest, and Northeast) where maintenance and pesticide budget correlated to pesticide risk and use intensity. However, there was a strong relationship between regulatory environment and pesticide risk across all regions. Pesticide risk was significantly lower in Norway, Denmark, and the UK, where twenty or fewer active ingredients were available to golf course superintendents, than it was in US where depending on the state between 200 and 250 pesticide active ingredients were registered for use on golf courses.

Managed turfgrass is a common component of urban landscapes that is expanding under current land use trends. Previous studies have reported high rates of soil carbon sequestration in turfgrass, but no systematic review has summarized these rates nor evaluated how they change as turfgrass ages. Here we conducted a meta-analysis of soil carbon sequestration rates from 63 studies globally, comprised mostly of C3 grass species in the U.S., including 24 chronosequence studies that evaluated carbon changes over 75 years or longer. We showed that turfgrass established within the last ten years had a positive mean soil C sequestration rate of 5.3 Mg CO2 ha(-1) yr(-1) (95% CI = 3.7-6.2), which is higher than rates reported for several soil conservation practices. Areas converted to turfgrass from forests were an exception, sometimes lost soil carbon, and had a cross-study mean sequestration rate that did not differ from 0. In some locations, soil C accumulated linearly with turfgrass age over several decades, but the major trend was for soil C accumulation rates to decline through time, reaching a cross-study mean sequestration rate that was not different from 0 at 50 years. We show that fitting soil C timeseries with a mechanistically derived function rather than purely empirical functions did not alter these conclusions, nor did employing equivalent soil mass versus fixed-depth carbon stock accounting. We conducted a partial greenhouse gas budget that estimated emissions from mowing, N-fertilizer production, and soil N2O emissions. When N fertilizer was applied, average maintenance emissions offset 32% of C sequestration in recently established turfgrass. Potential emission removals by turfgrass can be maximized with reduced-input management. Management decisions that avoid losing accrued soil C-both when turfgrass is first established and when it is eventually replaced with other land-uses-will also help maximize turfgrass C sequestration potential.

Microdochium patch is a turfgrass disease caused by the fungal pathogen Microdochium nivale. Iron sulfate heptahydrate (FeSO4•7H2O) and phosphorous acid (H3PO3) applications have previously been shown to suppress Microdochium patch on annual bluegrass putting greens when applied alone, although either disease suppression was inadequate or turfgrass quality was reduced from the applications. A field experiment was conducted in Corvallis, Oregon, U.S.A., to evaluate the combined effects of FeSO4•7H2O and H3PO3 on Microdochium patch suppression and annual bluegrass quality. The results of this work suggest that the addition of 3.7 kg H3PO3 ha-1 with 24 or 49 kg FeSO4•7H2O ha-1 applied every 2 weeks improved the suppression of Microdochium patch without substantially compromising turf quality, which occurred when 98 kg FeSO4•7H2O ha-1 was applied with or without H3PO3. Spray suspensions reduced the pH of the water carrier, therefore two additional growth chamber experiments were conducted to better understand the effects of these treatments on leaf surface pH and Microdochium patch suppression. On the application date in the first growth chamber experiment, at least a 19% leaf surface pH reduction was observed compared with the well water control when FeSO4•7H2O was applied alone. When 3.7 kg H3PO3 ha-1 was combined with FeSO4•7H2O, regardless of the rate, the leaf surface pH was reduced by at least 34%. The second growth chamber experiment determined that sulfuric acid (H2SO4) at a 0.5% spray solution rate was always in the group that produced the lowest annual bluegrass leaf surface pH, but did not suppress Microdochium patch. Together, these results suggest that while treatments decrease leaf surface pH, this decrease in pH is not responsible for the suppression of Microdochium patch.