Dollar spot, caused by fungi in the Clarireedia genus, is among the most economically important turfgrass diseases. One strategy for controlling dollar spot is the use of tolerant cultivars, which typically take longer to develop symptoms and have smaller lesion centers compared with more susceptible cultivars. We previously developed a quantitative PCR (qPCR) assay that can quantify the Clarireedia concentration in asymptomatic and symptomatic turfgrass. The goal of this 3-year study was to quantify the concentration of Clarireedia in a tolerant and susceptible cultivar of creeping bentgrass (Agrostis stolonifera) throughout the growing season to determine the effect host tolerance has on dollar spot development in the field. Turfgrass samples were collected weekly in 2019, 2020, and 2021 starting the first week of May and ending the second week of August for a duration of 15 weeks each year. The qPCR assay identified significant differences in Clarireedia concentration between the cultivars in both asymptomatic and symptomatic tissue. Linear model analysis showed the tolerant cultivar Declaration always had a lower Clarireedia concentration compared with the susceptible cultivar Independence. This supported our inhibition hypothesis that, although the concentration of Clarireedia required to cause symptoms was similar for both cultivars, the pathogen increased at a slower rate and therefore took longer to develop in a tolerant cultivar. The ability of the qPCR assay to quantify the concentration of Clarireedia in both asymptomatic and symptomatic tissue in the field during the growing season provides a tool for more in-depth epidemiological studies of dollar spot disease in turfgrass.

Wear stress can negatively impact the quality of creeping bentgrass (Agrostis stolonifera L.) putting greens. Phosphonate fungicides formulated with proprietary pigments often include label language indicating plant health benefits, such as alleviating abiotic and biotic stresses. The objective of this study was to determine whether pigmented phosphonate fungicides affect the wear response of creeping bentgrass managed as golf course putting green turf. Pigmented fosetyl-Al and pigmented K-phosphite were applied at 14-day intervals to 'Shark' creeping bentgrass managed as golf course putting green turf during May-July in 2017 and 2018 and subjected to wear. Wear reduced both qualitative and quantitative measurements on creeping bentgrass compared with no-wear plots. Treatment rankings for turf quality and turf color were pigmented fosetyl-Al > pigmented K-phosphite > nontreated. Creeping bentgrass treated with pigmented phosphonate fungicides and subjected to wear exhibited higher green cover and greater turf density compared with nontreated creeping bentgrass subjected to wear. Our research suggests that including pigmented phosphonate fungicides into fungicide rotations for turfgrass disease control may provide the additional benefit of mitigating wear stress.

Sand topdressing is the practice of applying a thin layer of sand to the surface of a turf. The history of sand topdressing dates back over a century on the Old Course at St. Andrews, Scotland. Sand topdressing is critical for improving root zone physical properties, supporting healthy root systems, and alleviating compaction stresses at the soil surface of highly trafficked turfs. A primary benefit of using non-amended sand for topdressing is to avoid adding additional organic matter when the management objective is to prevent excessive organic matter (thatch) accumulation. However, there is a long-running debate about whether topdressing alone is sufficient for organic matter control. The documentation of organic matter accumulation is limited. Multiple years are often needed for sufficient organic matter to accumulate and enable the detection of differences among topdressing treatments. In a three-year case study on an annual bluegrass (Poa annua) putting green turf, our data suggest that topdressing sand decreases organic matter content on a mass basis by diluting thatch and forming a mat layer. The growth of healthy turfgrass can contribute greatly to organic matter accumulation at the surface of the soil profile. Thus, a successful topdressing program needs consistent applications to match the growth pattern of turfgrass for the local climate. A more comprehensive understanding of organic matter build-up and its subsequent role in soil and plant health is needed. Cultural management solely based on thresholds of organic matter content in turfgrass systems does not acknowledge that other evaluations such as layering, root health, water infiltration, and surface firmness need to be carefully considered before implementing cultivation management practices to reduce organic matter.

Routine application of topdressing sand is widely practiced to manage putting green surfaces. Topdressing with finer sand and/or at minimal rates can enhance incorporation, greatly reducing the concerns of interference. A 7‐year field study investigated the effects of topdressing and cultivation practices on turf quality and surface characteristics of creeping bentgrass ( Agrostis stolonifera L.) grown on a sand‐based rootzone. A 3 × 2 × 2 factorial design evaluated sand size (medium‐coarse, medium‐fine, and fine‐medium), rate of topdressing during mid‐season (0.24 or 0.49 kg m −2 every 10–14 days), and cultivation (hollow tine cultivation [HTC] plus backfilled with medium‐coarse sand or noncultivated). Sand size and topdressing rate significantly affected turf quality, surface volumetric water content (VWC), and surface hardness, with their effects dependent on cultivation. Without HTC, VWC increased as the topdressing sand size became finer. However, when HTC was applied, VWC was not increased by topdressing with medium‐fine sand during any year. The practice of HTC also offset the effect of fine‐medium sand increasing VWC during the first 4 years, but not Years 5 through 7. Therefore, caution is needed when considering fine‐medium sand for topdressing putting greens. Additionally, after 5 years of treatment, the lower topdressing rate led to a wetter surface compared to the higher rate in the absence of cultivation, but not when HTC was applied. The major drawback of HTC was disruption of the turf surface, which resulted in better turf quality on noncultivated plots throughout the trial.

The effect of potassium on dollar spot of annual bluegrass (ABG; Poa annua L. forma reptans (Hausskn.) T. Koyama) and creeping bentgrass (CBG; Agrostis stolonifera L.) is poorly understood. Two field trials were conducted in 2020 and 2021 to determine the effect of K fertilization on dollar spot of ABG and CBG turf grown on a sand mat layer overlying a sandy loam (fine-loamy, mixed, semiactive, and mesic Typic Hapludults) and mowed at 2.8 mm. A 4 x 2 factorial, randomized complete block design evaluated K (potassium sulfate) applied at 0, 3.4, 6.9, and 13.8 kg ha-1 every 2 weeks and N (urea) applied at 4.9 kg ha-1 every 7 or 28 days over 20 weeks. Infection centers were counted over a 2-week period each year after inoculation with Clarireedia jacksonii in mid-September and used to calculate the disease severity. Increasing K fertilization rate consistently increased dollar spot severity on ABG and CBG. Higher N rate either slightly increased or did not affect disease severity on ABG, and either decreased or had no effect on CBG. This is the first study to document the impact of K fertilization on dollar spot severity of ABG turf. Regression analysis indicated that increases in both leaf tissue and mat layer K were associated with greater dollar spot severity on both species. Future research should determine whether the increased dollar spot response to K fertilization occurs at higher antecedent mat layer and leaf tissue K. Additionally, a broader range of N rates may clarify the dollar spot response.

Bentgrass ( Agrostis spp.) cultivars vary in resistance to dollar spot caused by Clarireedia jacksonii . Using a damage threshold to schedule fungicide applications has potential for reducing fungicide inputs. Two field trials managed as fairway turf in North Brunswick, NJ, from 2018 to 2021 assessed the effectiveness of damage threshold fungicide schedules to control dollar spot on bentgrass cultivars varying in disease resistance. Two factorially arranged randomized complete block designs (3 × 6 and 3 × 9, non‐inoculated and inoculated, respectively) were used. A fungicide scheduling factor included a calendar schedule and two damage threshold schedules that applied fungicides either within 24 h or the next application day (NAD) once a 105 mm 2 m −2 of symptomatic area was observed. The cultivar factor included six (Trial 1) and nine (Trial 2) bentgrass entries ranging from low to high dollar spot resistance. Damage threshold schedules on the resistant cultivar Declaration reduced fungicide inputs up to 78% compared to the calendar schedule. Reduced fungicide inputs for each cultivar were achieved by delaying disease onset in the non‐inoculated trial and extending the application interval in both trials. The 24‐h threshold schedule controlled dollar spot equivalent to the calendar schedule on more resistant cultivars. There was a lower risk of severe disease outbreaks when threshold applications were applied on the NAD schedule compared to the calendar schedule on the resistant cultivars. Thus, using a low damage threshold to apply fungicides on resistant bentgrass can effectively control dollar spot with fewer fungicide inputs.

Creeping bentgrass (CB; Agrostis stolonifera L.) grows well in low phosphorus (P) soils in monoculture, however, the soil P concentration range that provides CB an advantage over annual bluegrass (AB; Poa annua L.) in mixed swards is unknown. The objective of this research was to determine how P and soil pH influence species composition when AB and CB are established from tillers in polyculture. Replicate greenhouse experiments evaluated five P rates (0, 3, 6, 9, and 12 kg ha(-1) P via triple superphosphate) and two soil pH levels (5.6 and 7.1). The highest P rate in the high pH soil resulted in the most AB cover (61%). Phosphate applied at 3 kg ha(-1) P in the low pH soil provided the greatest CB cover (72%), which was fivefold greater than AB cover. All P-receiving treatments in the low pH soil had similar green cover, but a species advantage for CB was only observed in the 3 kg ha(-1) P treatment. Turfgrass quality was greatest when >= 6 kg ha(-1) P was applied to low pH soil but was only slightly reduced at 3 kg ha(-1) P. Regardless of pH, withholding P resulted in the lowest AB cover (<4%); however, these treatments resulted in poor turfgrass quality and low green cover (<30%). Aboveground shoot biomass increased linearly with P rate and was greater at the lower pH. In moderately acidic sand, AB was less competitive than CB when Mehlich-3 P ranged from 4 to 6 mg kg(-1).

Turfgrasses are susceptible to a wide variety of ectotrophic root-infecting (ERI) fungi that cause root rot (Tredway et al., 2023). Among the root rot diseases, fairway patch, caused by Phialocephala bamuru P.T.W. Wong & C. Dong sp. nov., was recently identified and characterized in Australia infecting bermudagrass (Cynodon dactylon) and kikuyu (Pennisetum clandestinum) grass (Wong et al., 2015). Symptoms begin as small, 5-10 cm diameter patches of yellowed turf that may coalesce into larger areas of diseased grass. A characteristic sign of fairway patch is roots colonized by dark brown to black, ectotrophic mycelium. In June 2020, many tan colored, irregular-shaped patches ranging from 10-30 cm in diameter developed on a hard fescue (Festuca brevipila) cultivar 'Beacon' turfgrass field in North Brunswick, New Jersey, USA. The centers of these patches later died and became sunken or filled in partially by recovering hard fescue. The patches grew into tan irregular-shaped rings with diameters up to 3 m by Aug 2023. Symptoms were indicative of a root disease. Five 'Beacon' hard fescue soil cores at the interface of the symptomatic and non-symptomatic area were sampled in Aug 2023. Root and crown samples were observed under a dissecting microscope and dark ectotrophic hyphae were observed on both. Roots with visible ectotrophic mycelium were removed, rinsed in sterile water three times, cut into 5 mm pieces, and plated onto 10% potato dextrose agar amended with streptomycin and gentamicin at 100 mg/L (PDA+). The plates were incubated at 25°C in the dark for 5 days. The most abundant colonies being characteristic long, septate hyphae that were hyaline at the edge and dark brown to black in the center and resembled the fungus described in Wong et al., 2015. These colonies were subcultured onto PDA+ medium and selected for molecular identification. Other less abundant colonies could be identified using morphology after subcultured and had no record being pathogenic to turfgrass. To confirm the isolate's identity, its internal transcribed spacer (ITS) region was amplified in PCR using the ITS1F/ITS4 primers (Bellemain et al., 2010). The amplicon was then sequenced with both ITS1 and ITS4 primers by Sanger sequencing. Sequences were assembled (GenBank #PP000819). The consensus sequence was then BLASTn analyzed with default settings, and the result showed 99.64% sequence identity with P. bamuru (GenBank #MG195534.1). Koch's postulate was conducted in an environmentally controlled growth chamber. Six healthy 'Beacon' hard fescue plugs were sampled from the field. Three of the six plugs (treatment) were each inoculated with P. bamuru by placing 20 g of P. bamuru colonized millets beneath and around the plug before filling the pots with sand. The other three plugs (control) received the same treatment except the P. bamuru colonized millets were autoclaved. The pots were incubated in the growth chamber with a 16 h light period and 25/20°C day/night temperatures. Symptoms resembling those observed in the field appeared on the treatment pots after 21 days of incubation while the control pots remained healthy. The roots from the treatment pots were examined under the dissecting microscope to confirm the colonization of P. bamuru on the roots, and P. bamuru was reisolated and confirmed using the aforementioned morphological traits and molecular assays (GenBank #PP000820). This is the first report of a turfgrass root rot disease caused by P. bamuru in the United States. Further epidemiological, disease ecological, and pathogen biological studies are required to clarify the importance of this disease in the United States and establish proper disease containment or control measures.

Annual bluegrass (Poa annua L.) is sensitive to high-temperature stress, and approaches that can improve plant growth during summer months are important for golf courses managing P. annua putting greens. The objective of this 2-year field trial was to determine plant health benefits for selected fungicides and the combination with a plant growth regulator (PGR), trinexapac-ethyl (TE) on P. annua growth under putting green conditions during summer months. The following treatments were foliar sprayed at 14-day intervals from June to September in 2020 and 2021: (1) untreated control with water, (2) Daconil Action, (3) Appear II, (4) Daconil Action and Appear II, and (5) Daconil Action, Appear II, and Primo Maxx (TE). Applying individual and combination treatments resulted in significant improvements on P. annua summer performance, as manifested by increased visual turf quality and other vegetation indices evaluated using multispectral radiometer (normalized difference vegetation index, leaf area index, and stress index or digital camera [percent canopy cover and dark green color index]) in both years. The combined treatment programs, Daconil Action and Appear II or Daconil Action, Appear II, and Primo Maxx were more effective than the untreated control and each individual treatment. The results suggest that there existed synergistic effects of multiple fungicides and PGR, which could be particularly useful in promoting plant health of P. annua under heat stress conditions.

Dollar spot is an important disease of both cool- and warm-season turfgrasses caused by six fungal species in the genus Clarireedia, yet the ecology and epidemiology of these pathogens remains poorly understood. The goal of this study was to determine the distribution of Clarireedia in asymptomatic and symptomatic creeping bentgrass (Agrostis stolonifera) in the field using a previously developed quantitative PCR assay. To determine the horizontal distribution of the pathogen, the abundance of Clarireedia spp. was measured in leaf and crown tissue from 90, 1-cm-diameter cores spaced 10 cm apart in May 2019 and 2020 (asymptomatic tissue) and August 2019 and July 2020 (symptomatic tissue). Thirty-seven to 69% of cores sampled from asymptomatic turfgrass and 77 to 95% of cores taken from symptomatic turfgrass yielded positive detections for Clarireedia. Spatial analysis indicated that Clarireedia was randomly distributed in the field in both asymptomatic and symptomatic turfgrass. To assess the vertical distribution of the pathogen, the abundance of Clarireedia was measured in the foliar, crown, and thatch layers of 39, 1-cm-diameter × 2.5-cm-deep cores of creeping bentgrass maintained at fairway height (9.5 mm) during 2019 and 2020. Clarireedia was most abundant in foliar tissue, followed by crown tissue and thatch (lowest abundance) throughout the 2-year study. Both studies provide evidence that Clarireedia is widely distributed in turfgrass swards prior to symptom development and can persist within turfgrass as an endophyte. These findings will improve our understanding of Clarireedia epidemiology and may lead to more sustainable dollar spot management.

Fine fescues are a group of turfgrass species that are often planted when low-input maintenance is desired. The five species most commonly associated with the fine fescues are strong creeping red fescue, slender creeping red fescue, Chewings fescue, sheep fescue, and hard fescue. Little is known about the resistance of fine fescues to snow mold diseases despite the widespread adoption of fine fescues across temperate climates with harsh winters. Field and controlled environment trials were conducted in Wisconsin and New Jersey between 2014 and 2017 to assess snow mold resistance among the fine fescues. In both the field and controlled environments, hard and sheep fescue were among the most resistant to snow molds, and Chewings fescue was the most susceptible. However, significant variation existed among the cultivars within each species, suggesting that opportunities exist for breeding to improve resistance to snow mold in the fine fescues.

Magnaporthiopsis meyeri-festucae is a recently identified root-infecting pathogen of fine fescue (Festuca spp.) turfgrasses. Although it is phylogenetically similar to other root-infecting turfgrass pathogens such as M. poae, management of M. meyeri-festucae is distinct and highlights the need for fast and accurate identification. The objective of this study was to develop a rapid detection method for M. meyeri-festucae using recombinase polymerase amplification (RPA) to assist turfgrass managers in identifying the disease in the field and facilitate further epidemiological research on the pathogen. Three isolates of M. meyeri-festucae and eight isolates from four related Magnaporthiopsis species were used to test the specificity of the RPA assay targeting M. meyeri-festucae. Rapid visualization of the RPA assay results using a mixture of purified amplicon and SYBR-Safe fluorescence emitting asymmetrical cyanine dye showed that the assay was effective at detecting M. meyeri-festucae on turfgrass roots with no observed incidence of false positives or false negatives. The assay also differentiated between M. meyeri-festucae and other Magnaporthiopsis species, although overall sensitivity was lower compared with a PCR-based method. The RPA assay successfully detected M. meyeri-festucae following inoculation onto and grinding of turfgrass roots, indicating possible use as a rapid field diagnostic tool for turfgrass managers. The fast and accurate RPA M. meyeri-festucae detection method presented here will be used for additional field and laboratory applications that will help improve the management of this emerging pathogen.

The 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.

Gray leaf spot, caused by the fungal pathogen Pyricularia oryzae , is a widespread and destructive foliar disease of turfgrasses in the United States. Characteristic gray leaf spot disease symptoms were observed on hard fescue ( Festuca brevipila Tracey) turf in New Jersey during October 2018. Prior to this observation, P. oryzae had not been documented as a pathogen of F. brevipila . Therefore, this study was conducted to determine if P. oryzae was the cause of the observed gray leaf spot disease symptoms. Morphological assessments and molecular analyses identified fungal isolates as the potential incitant from symptomatic F. brevipila turf as P. oryzae . Two isolates of P. oryzae (D300452 and 181001P12) and two F. brevipila cultivars (‘Beacon’ and ‘Reliant IV’) were used in growth chamber studies to fulfill Koch’s postulates for pathogenicity. Inoculations were carried out using conidial suspensions at 4 × 10 4 conidia ml − 1 concentration. Disease symptoms were observed 7 d post-inoculation for both isolates on both cultivars. Koch’s postulates were fulfilled by morphological evaluations and DNA sequencing of the reisolated fungi. This study confirms that P. oryzae is the causal agent of gray leaf spot disease on F. brevipila . Given the historical significance of gray leaf spot disease in other turf species, this study suggests that gray leaf spot could be a major concern for managing F. brevipila turf in the future.

There is a need to identify turfgrass species and mixtures for golf course fairways that can be managed sustainably with reduced fertility, pesticides, and irrigation. The current study evaluated Agrostis stolonifera L. (creeping bentgrass [AST]), Agrostis capillaris L. (colonial bentgrass [ACP]), Agrostis canina L. (velvet bentgrass [ACN]), Festuca rubra L. ssp. commutata Gaudin (Chewings fescue [FRC]), Festuca brevipila Tracey (hard fescue [FBP]), and Festuca rubra L. ssp. littoralis (G. Mey) Auquier (slender creeping red fescue [FRL]) planted as monostands and in mixtures to determine the ideal choice for low maintenance fairway management. Plots were established in the fall of 2014 in a randomized complete block design with three replications. Turf quality and disease resistance were evaluated visually from 2015–2018. Divots were mechanically created during the growing seasons of 2017 and 2018 and evaluated visually for initial divot injury and recovery every two weeks. Monostands and mixtures of ACN had the best turf quality and least brown patch (caused by Rhizoctonia solani Kühn) but took longer to recover from divots. A. capillaris monostands and mixtures exhibited above average turf quality but were more susceptible to brown patch disease. Compared to all other entries, monostands and mixtures of AST had the lowest turf quality and most dollar spot (caused by Clarireedia jacksonii C. Salgado, L.A. Beirn, B.B. Clarke, & J.A. Crouch sp. nov.). Festuca L. spp. (fine fescue spp.), when mixed with improved ACP cultivars such as ‘Puritan’ and ‘Capri’, exhibited above average turf quality but had below average performance in monostands or when combined with older ACP cultivars such as SR 7100. Divot resistance and recovery were variable between years but the FRL cultivar Shoreline and most FRC cultivars recovered quickly in both years, while ACP cultivar Capri and FBP cultivar Beacon were slow to recover in both years. Most species and mixtures were comparable and, in some cases, better than AST for divot recovery indicating that the alternative species tested in this study could provide sustainable turfgrass management on golf course fairways.

Exploring the reduction of recalcitrance in lignocellulosic feedstocks using fungal-induced degradation and associated impacts in molecular structure.

Research is lacking on best establishment practices of fine fescues (Festuca spp.), such as optimal seeding timings, which are well known for other cool-season turfgrasses. Our objective was to document establishment and determine optimal seeding timings for mixed stand of fine fescue in multiple cool-season climate zones in the United States. From 2019 to 2020, an experiment was replicated across four locations in the northern United States to investigate nine monthly fine fescue mixture seeding timings from March through November. Fine fescue seedling emergence typically hastened as temperatures increased during the growing season, and emergence required 6.1-9.4 d when soil temperatures were within a range of 15-25 degrees C. Final grid count data across multiple sites indicated that seeding fine fescues in August, September, and at times, July, will likely produce the best establishment with the lowest weed infestation pressure, and there may be more flexibility in seeding timings in a Mediterranean climate, such as Oregon. Seeding fine fescues in the early-spring or late-autumn can be more unreliable because of greater likelihood of weed infestation, suboptimal growing conditions, and potential of a late-autumn seeding to act as an unintended dormant seeding. Results indicate the weed invasion pressure of specific weeds will vary depending life cycle of weed and seeding time of year. Overall, seeding a fine fescue mixture in August or September will increase likelihood of success in cool-season climate zones in the United States with a wider seeding window when planting in Mediterranean climates.

Dollar spot (Clarireedia jacksonii) susceptibility varies among bentgrasses (Agrostis spp.). This trial assessed the ability of five action thresholds of the risk index (RI) of a logistic regression model to forecast dollar spot incidence on bentgrass fairway turf grown on a sandy loam in North Brunswick, NJ. Dollar spot incidence was assessed over 128 observation periods (May to Nov. annually) over 3 yr and related to five action thresholds for prediction accuracy. Action thresholds included a RI threshold of 20% (RI 20%), interpreting the change in the RI over time (RI slope), adjusting the RI upwards to maximize accuracy (RImax), combining RI 20% with RI slope, and combining RImax with RI slope. The RI 20% accurately predicted disease on 63 to 66% of observation periods for highly susceptible creeping bentgrass (A. stolonifera L.) cultivars Shark, Penncross, and Independence; other action thresholds improved accuracy by only 10% or less for these cultivars. Prediction accuracy on lower susceptibility cultivars (007, Declaration, and colonial bentgrass Capri; A. capillaris L.) was substantially improved with four novel action thresholds by reducing over-predictions compared to RI 20%. Accuracy was improved by as much as 32% when the RImax and RI slope were combined for Declaration compared to RI 20%. On low susceptibility cultivars, turf managers may be able to use action thresholds that incorporate a RI greater than 20% and/or RI slope to reduce fungicide inputs and maintain acceptable dollar spot control compared to RI 20%.