Abstract
Spring dead spot (SDS), caused by Ophiosphaerella spp., is among the most damaging diseases to hybrid bermudagrass (Cynodon dactylon × transvaalensis) in areas where winter dormancy occurs. Management strategies that aid in turfgrass recovery from SDS damage have not been widely studied. An experiment was conducted in Blacksburg, VA, in 2019 and 2020, to determine the influence of various cultural practices on bermudagrass recovery from SDS damage. Fertility and cultivation were applied in the late spring/early summer, which is earlier than normal for cultivation practices for bermudagrass, to test their effectiveness in aiding bermudagrass recovery from SDS damage. The main effects of fertility and cultivation were arranged in a 2 × 3 factorial design with vertical mowing, solid-tine aerification, and no cultivation applied with urea (48.8 kg⋅ha−1 N) sprayed at trial initiation and 2 weeks later or without urea. Plots were assessed for the percent of SDS throughout the study. Data were analyzed as the percent change relative to the initial assessment to measure bermudagrass recovery. The main effect of fertility increased bermudagrass recovery from SDS damage in both 2019 and 2020. The main effects of vertical mowing and solid-tine aerification reduced bermudagrass recovery from SDS damage in 2020. These data suggest that two properly timed nitrogen fertilization applications at 48.8 kg⋅ha−1 optimized bermudagrass recovery from SDS damage, whereas late spring/early summer cultivation without fertility may inhibit bermudagrass recovery.
Spring dead spot (SDS), caused primarily by Ophiosphaerella herpotricha J. Walker, O. korrae (J. Walker & A.M. Smith), Shoemaker & C.E. Babcock (=Leptosphaeria korrae J. Walker & A.M. Smith), and O. narmari (J. Walker & A.M. Smith) Wetzel, Hulbert, & Tisserat (=L. narmari J. Walker & A.M. Smith) in the United States, is a common and detrimental patch disease of hybrid bermudagrass [Cynodon dactylon (L.) Pers. × transvaalensis Burtt Davy] home lawns, athletic fields, and golf courses in areas where winter dormancy occurs. Patches appear sunken, necrotic, and straw-colored (Wadsworth and Young, 1960). The sunken nature of the patches decreases not only the aesthetics but also the surface playability and player safety of hybrid bermudagrass for golf and other sport uses (Martin et al., 2001). Many preventative chemical and cultural practices are used to mitigate this disease.
Fungicide treatment is one of the primary management strategies for SDS prevention. Fungicides targeted at SDS are typically applied in the fall, when soil temperatures are between 15.5 and 26.7 °C (Butler and Tredway, 2006). Fungicide efficacy against SDS has been sporadic, and efforts to increase fungicide efficacy through various application methods have produced mixed results (Beck et al., 2012; Butler and Tredway, 2006; Earlywine and Miller, 2015; Tredway et al., 2009b; Walker, 2013). New chemistries, particularly within the demethylase inhibitor and succinate dehydrogenase inhibitor fungicide classes, are effective at inhibiting Ophiosphaerella spp. growth (Hutchens et al., 2019). However, the cost of these newer fungicides may be a limiting factor for some turfgrass managers.
Cultural practices are frequently used by turfgrass managers to prevent SDS, and an abundance of research has been conducted with mixed results (Tredway et al., 2009b). Miller et al. (2017) showed that nitrogen and manganese sources had no effect on SDS severity the following year, whereas other studies demonstrated that the nitrogen source differentially affected O. herpotricha and O. korrae (Tredway et al., 2009a, 2020). Dernoeden et al. (1991) found that potassium chloride can increase the survivability of bermudagrass inoculated with O. korrae; however, McCarty et al. (1992) determined that potassium sulfate actually increased SDS severity. Moreover, lowering pH with fertilizers such as ammonium sulfate has been shown to reduce SDS symptoms in the field and suppress mycelial growth in vitro (Cottrill et al., 2016; Dernoeden et al., 1991; Tredway et al., 2020). Furthermore, there is documented evidence of a positive correlation between pH and SDS severity, particularly with O. herpotricha (Dernoeden et al., 1991; Tredway et al., 2020). Cold tolerance of bermudagrass cultivars was positively correlated with reduced SDS in certain studies, yet cold-tolerant cultivars are not entirely immune from damage (Baird et al., 1998; Iriarte et al., 2005a, 2005b; Martinez et al., 2014). Cultivation practices that remove thatch such as fraze mowing, sod stripping, and aerification plus vertical mowing during the summer can reduce SDS development the following spring (Miller et al., 2017; Tisserat and Fry, 1997). In contrast, vertical mowing or core aerifying was also demonstrated to increase SDS severity the following spring compared with a nontreated control (Perry et al., 2010). The results regarding the effect of cultivation practices on SDS prevention are unclear.
Research of curative and recuperative management strategies for symptomatic bermudagrass is limited. Studies have focused on which fertilizers most effectively increase bermudagrass recovery from SDS. Dernoeden et al. (1991) found that ammonium-based fertilizers generally provided the greatest SDS recovery. The authors reported one rating date at the Denton, MD, location: a fertilizer treatment of (NH4)2SO4 provided greater bermudagrass recovery from SDS damage than NaNO3, NH4Cl, CO(NH2)2, NaNO3 plus KCl, and CO(NH2)2 plus KCl, and no fertility while the NaNO3 plus KCl treatment provided the least recovery. However, the authors reported conflicting results at the Silver Spring, MD location, with all fertility treatments similarly increasing bermudagrass recovery compared with the nontreated control, with the exception of KCl. Ascocarps of O. korrae were observed at the Silver Spring location, but no attempt at identifying the Ophiosphaerella species at the Denton location was performed (Dernoeden et al., 1991). Polymerase chain reaction methods for identifying Ophiosphaerella species were not available during the time of the Dernoeden et al. (1991) study; therefore, identification of the species was more difficult. Recent data from our laboratory that were gathered using species-specific primers developed by Tisserat et al. (1994) and Martinez et al. (2019) suggested that O. korrae is predominantly isolated from the Silver Spring area, whereas O. herpotricha is predominant on the eastern shore of Maryland, where Denton is located, with 62% of the 42 samples collected from the eastern shore of Maryland amplifying O. herpotricha (Hutchens et al., 2021). Potential differences in the Ophiosphaerella species may be the cause of the discrepancies in bermudagrass recovery between the two locations in this study.
There has been research of the effects of preventative applications of fertility and cultivation on SDS caused by O. herpotricha, but there is no documented research of the influence of therapeutic cultivation and fertility applications on bermudagrass recovery during the growing season from SDS caused by O. herpotricha (Dernoeden et al., 1991; Miller et al., 2017; Tisserat and Fry, 1997; Tredway et al., 2009a, 2020). Most research efforts addressing the influence of cultivation practices on SDS have been aimed at the prevention of SDS the following spring (Miller et al., 2017; Tisserat and Fry, 1997). Based on a review of the literature, there have been no studies of how cultivation practices such as vertical mowing and solid-tine aerification affect bermudagrass recovery from SDS within the same growing season. Moreover, SDS patches can be slow to recover because of the use of certain preemergence herbicides or metabolites produced by the pathogen that can inhibit shoot regrowth (Beck et al., 2013; Fermanian et al., 1981; Venkatasubbaiah et al., 1994). Therefore, methods to aid in bermudagrass recovery from SDS damage are needed. The objective of our studies was to determine how implementation of late spring/early summer vertical mowing, solid-tine aerification, and urea (46–0–0) applications influence bermudagrass recovery from SDS within the same growing season.
Materials and Methods
Site description.
A field study of SDS symptomatic ‘Latitude 36’ hybrid bermudagrass at the Virginia Tech Practice Football Field (VTPFF), Blacksburg, VA, and SDS symptomatic ‘NorthBridge’ hybrid bermudagrass at Blacksburg Country Club (BCC), Blacksburg, VA, growing in urban soils was conducted. Based on a recently conducted Ophiosphaerella species geographic distribution study, O. herpotricha is primarily isolated in the Blacksburg area, where both of our study sites are located (Hutchens et al., 2021). Studies were conducted at the VTPFF from 24 May 2019 to 2 Aug. 2019, and repeated the following year from 25 June 2020 to 6 Aug. 2020. Studies at BCC were conducted from 30 May 2019 to 12 Aug. 2019, and repeated the following year from 25 June 2020 to 6 Aug. 2020. The Latitude 36 hybrid bermudagrass at the VTPFF was maintained at 1.3 cm with an irrigation regiment sufficient to maintain turf vigor and prevent wilt, whereas the NorthBridge hybrid bermudagrass at BCC was maintained at 1.3 cm with no supplemental irrigation. No preventative SDS fungicide applications were made at either study site.
Study design and treatments.
In both studies, the main effects of fertility and cultivation were arranged in a 2 × 3 factorial design in complete blocks with vertical mowing at a 1-cm depth from the soil surface, solid-tine aerification with 16-mm diameter tines at a 5.7-cm depth, and no cultivation applied with urea (48.8 kg⋅ha−1 N) sprayed at trial initiation and 2 weeks later or without urea. There were four replications, and treatments were applied to 1.8-m × 1.8-m plots with a CO2-pressurized sprayer delivering solution at 276 kPa of pressure at a carrier volume of 842 L⋅ha−1. Urea treatments were irrigated within 1 h after application in an attempt to prevent severe foliar burn from the fertilizer. Individual treatments are listed in Table 1. The same plots for each treatment were used in both study years.
Treatments for spring dead spot recovery trials at Blacksburg Country Club and the Virginia Tech Practice Football Field.
Data collection and analysis.
Plots were visually assessed every 1 to 2 weeks throughout the duration of the study to determine the percent SDS. The percent SDS was measured as the percent area of the plot expressing sunken and/or necrotic patches with at least a 7.6-cm diameter area of necrosis. All data were transformed to percent change relative to the initial assessment within the plot. The additive inverse of the percent change relative to the initial assessment is equal to the percent bermudagrass recovery. The equation was as follows (n is equal to any given assessment date): Percent recovery = [(AssessmentInitial − Assessmentn)/AssessmentInitial] × 100. Initial assessments were performed on the day of study initiation. The range of the initial percent SDS within each plot at each location was as follows: VTPFF in 2019 (1% to 18%), VTPFF in 2020 (0.6% to 20%), BCC in 2019 (2% to 35%), and BCC in 2020 (1.5% to 20%). Final assessments were performed on 2 Aug. 2019 and 6 Aug. 2020 at VTPFF, and on 12 Aug. 2019 and 6 Aug. 2020 at BCC. The relative percent SDS compared with the initial SDS (i.e., percent recovery) was converted to the area under the disease progress curve to encompass the factor of time and bermudagrass recovery from SDS damage. The main effects were separated by year for each location. Data were subjected to an analysis of variance and means were separated using Student’s t test. Means were separated with a significance level of P ≤ 0.1 in JMP Pro 15 (SAS Institute, Cary, NC).
Results
The main effect of fertility increased bermudagrass recovery in both 2019 and 2020 (P ≤ 0.0417) at BCC (Table 2). In 2019, fertility increased bermudagrass recovery by 19% compared with nonfertilized plots (Fig. 1). Similarly, in 2020, fertility increased bermudagrass recovery by 33% compared with nonfertilized plots (Fig. 1). The main effect of fertility influenced bermudagrass recovery (P = 0.0629) at VTPFF in 2019, but fertility did not influence bermudagrass recovery in 2020 (P = 0.4907) (Table 3). Fertility increased bermudagrass recovery by 40% in 2019 at VTPFF (Fig. 2).
Main effect of fertility on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Blacksburg Country Club in 2019 and 2020. Different color bars represent different fertility practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.05).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of fertility on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Blacksburg Country Club in 2019 and 2020. Different color bars represent different fertility practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.05).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of fertility on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Blacksburg Country Club in 2019 and 2020. Different color bars represent different fertility practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.05).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of fertility on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Virginia Tech Practice Football Field in 2019 and 2020. Different color bars represent different fertility practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.1).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of fertility on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Virginia Tech Practice Football Field in 2019 and 2020. Different color bars represent different fertility practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.1).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of fertility on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Virginia Tech Practice Football Field in 2019 and 2020. Different color bars represent different fertility practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.1).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Analysis of variance for main effects of fertilization, main effects of cultivation, and interaction effects on bermudagrass recovery from spring dead spot at Blacksburg Country Club in 2019 and 2020.
Analysis of variance for main effects of fertilization, main effects of cultivation, and interaction effects on bermudagrass recovery from spring dead spot at Virginia Tech Practice Football Field in 2019 and 2020.
Although there were negative trends on bermudagrass recovery in both years at BCC, cultivation practice did not have a significant effect on bermudagrass recovery in 2019 (P = 0.2023), but it did negatively impact bermudagrass recovery in 2020 (P = 0.0071) (Table 2). Bermudagrass recovery for solid-tine aerification and vertical mowing were not significantly different, and both cultivation practices reduced bermudagrass recovery by >32% compared with no cultivation (Fig. 3). There was no significant main effect of cultivation at VTPFF in 2019 (P = 0.6420) or 2020 (P = 0.5304) (Table 3), but the trends were similar to BCC with solid-tine aerification and vertical mowing numerically reducing bermudagrass recovery. There were no fertility × cultivation effects at BCC or VTPFF.
Main effect of cultivation practice on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Blacksburg Country Club in 2019 and 2020. Different color bars represent different cultivation practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.05).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of cultivation practice on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Blacksburg Country Club in 2019 and 2020. Different color bars represent different cultivation practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.05).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Main effect of cultivation practice on the percent bermudagrass recovery area under the disease progress curve (AUDPC) at Blacksburg Country Club in 2019 and 2020. Different color bars represent different cultivation practices. Means are compared within the year. Bars with different letters are significantly different (P < 0.05).
Citation: HortScience 57, 2; 10.21273/HORTSCI16235-21
Discussion
Our data suggest that late spring/early summer nitrogen applications are beneficial to turf recovery from SDS damage. Dernoeden et al. (1991) observed findings similar to those of our studies, with spring/summer applications of nitrogen increasing bermudagrass recovery from SDS damage. The authors showed that all sources of nitrogen evaluated enhanced turf recovery from SDS damage, yet the rate of recovery compared with a nontreated control differed among nitrogen sources. We found that late spring/early summer applications of urea were beneficial for turf recovery from SDS damage, suggesting that nitrogen is the key nutrient for turf recovery. Similarly, Dernoeden et al. (1991) showed that urea increased bermudagrass recovery from SDS. This has been documented for dead spot of creeping bentgrass (Ophiosphaerella agrostis) as well (Kaminski and Dernoeden, 2005).
We observed that plots treated with fertility in 2019 had less initial SDS in 2020 relative to the initial SDS in 2019 (P = 0.0718) at VTPFF (data not shown). This provides further support that nitrogen applications could be beneficial for SDS suppression; however, no significant reduction of SDS in 2020 from fertility applications in 2019 at BCC were observed (data not shown). Ammonium sulfate and calcium nitrate applications have also been shown to reduce SDS damage, depending on which Ophiosphaerella species is present (Dernoeden et al., 1991; Tredway et al., 2020). Our results are different from what McCarty et al. (1992) reported, with sulfur-coated urea increasing SDS up to 128%. Nitrogen applications in our study were made in late spring/early summer, whereas nitrogen applications used during the McCarty et al. (1992) study were made in the fall, offering a potential reason for the different results. Moreover, the addition of sulfur to the plant by using sulfur-coated urea in one study (McCarty et al., 1992) may have been the reason for the increased SDS, and this was also documented in another study (Perry et al., 2010).
Urea is a cost-effective fertilizer, but it only provides nitrogen to the plant; misapplications can cause phytotoxicity because of its high water solubility (Krogmeier et al., 1989). Less soluble fertilizers delivering nitrogen, as well as other required macronutrients or micronutrients, may be better options than urea on bermudagrass in the late spring/early summer to enhance overall bermudagrass health as well as recovery from SDS damage. Further research of the effects of the nitrogen source, other nutrients, and application timing on bermudagrass recovery and prevention from SDS damage needs to be conducted.
Our study showed that cultivation was inhibitory to bermudagrass recovery at BCC, but not at VTPFF. The VTPFF location was more intensively managed than the BCC location, which may have reduced the inhibitory effects of cultivation on bermudagrass recovery from SDS. No research of the influence of cultivation practices on SDS recovery within the same season has been published, but research of the use of cultivation practices for the prevention of SDS is well-documented. Tisserat and Fry (1997) showed that vertical mowing or aerifying alone did not reduce SDS symptom expression the following spring, which is similar to what we observed (data not shown). However, they demonstrated that the combination of vertical mowing and aerifying did reduce SDS symptom expression the following spring. Miller et al. (2017) showed similar results with treatments using the highly disruptive fraze mower. In contrast, Perry et al. (2010) demonstrated that core aerifying or vertical mowing in the summer can increase SDS the following spring. However, the effects of increased SDS with cultivation practices were only observed during 1 year of a 3-year study (Perry et al., 2010). The Tisserat and Fry (1997) and Miller et al. (2017) studies suggested that highly disruptive cultivation practices are beneficial for preventing SDS the following season, which is likely because of thatch reduction and removal, increased oxygen to the root zone, and generation of new growing points on the plant. Our data suggest that early season cultivation, particularly in the absence of fertility, can decrease bermudagrass recovery from SDS within the same season. Although disruptive cultivation practices can be beneficial for the prevention of SDS, they do not aid in bermudagrass recovery from SDS damage within the same season, particularly in the absence of nitrogen fertility.
Our data indicate that up to 97.6 kg⋅ha−1 N from urea applied over a 2-week period in late spring/early summer greatly accelerated bermudagrass recovery from SDS. Cultivation practices should be implemented after bermudagrass has mostly recovered from SDS damage, which often occurs during midsummer. If 97.6 kg⋅ha−1 N is applied in late spring and cultivation is conducted in midsummer, then bermudagrass recovery from SDS damage should be optimized. However, more research needs to be conducted to determine the effects of various nitrogen sources and application timings on bermudagrass recovery from SDS damage.
Literature Cited
Baird, J.H., Martin, D.L., Taliaferro, C.M., Payton, M.E. & Tisserat, N.A. 1998 Bermuda- grass resistance to spring dead spot caused by Ophiosphaerella herpotricha Plant Dis. 82 771 774 https://doi.org/10.1094/PDIS.1998.82.7.771
Beck, L.L., Cooper, T., Hephner, A.J., Straw, C.M. & Henry, G.M. 2013 Effect of preemergence herbicides on the recovery of bermudagrass from spring dead spot Appl. Turfgrass Sci. 10 https://doi.org/10.1094/ATS-2013-0328-01-RS
Beck, L.L., Moore-Kucera, J., Henry, G., Woodward, J., Zak, J. & Cox, R. 2012 Evaluation of chemical and cultural methods for the management of spring dead spot in bermudagrass Turf Dissertation. Texas Tech Univ., Lubbock, TX. <https://ttu-ir.tdl.org/bitstream/handle/2346/50750/Beck_Leslie_Diss.pdf?sequence=1&isAllowed=y>
Butler, E.L. & Tredway, L.P. 2006 Method and timing of fungicide applications for control of spring dead spot in hybrid bermudagrass. Online Plant Health Prog. https://doi.org/10.1094/PHP-2006-0901-01-RS
Cottrill, D.J., Earlywine, D.T. & Miller, G.L. 2016 Assessment of nitrogen source, sulfur, and fall fungicide applications on the management of spring dead spot of bermudagrass Plant Dis. 100 473 482 https://doi.org/10.1094/PDIS-05-15-0565-RE
Dernoeden, P.H., Crahay, J.N. & Davis, D.B. 1991 Spring dead spot and bermudagrass quality as influenced by nitrogen source and potassium Crop Sci. 31 1674 1680 https://doi.org/10.2135/cropsci1991.0011183X003100060058x
Earlywine, D.T. & Miller, G.L. 2015 Evaluation of multiple fungicides in combination with a wetting agent for spring dead spot control on bermudagrass, 2013-2014 Plant Dis. Manag. Rep. 9 T018
Fermanian, T.W., Ahring, R.M. & Huffine, W.W. 1981 The isolation of a toxin from spring dead spot areas in bermudagrass (Cynodon L.C. Rich) turf Int. Turfgrass Soc. Res. J. 4 433 441
Hutchens, W.J., Henderson, C.A., Bush, E.A., Kerns, J.P. & McCall, D.S. 2021 Geographic distribution of Ophiosphaerella species in the mid-Atlantic United States Plant Health Prog. https://doi.org/10.1094/PHP-04-21-0076-S
Hutchens, W.J., Nagaoka, Y., Kerns, J.P., Goatley, J.M., Nita, M. & McCall, D.S. 2019 Variable sensitivity of Ophiosphaerella spp. causing spring dead spot to fungicides and temperature Abstract Crop Science Society of America Annual Meeting 2019
Iriarte, F.B., Wetzel, H.C. III, Fry, J.D., Martin, D.L., Vincelli, P., Dixon, E.W. & Tisserat, N.A. 2005a Aggressiveness of spring dead spot pathogens to bermudagrass Int. Turf. Res. J. 10 258 264
Iriarte, F.B., Fry, J.D., Martin, D.L., Todd, T.C. & Tisserat, N.A. 2005b Effect of cold acclimation and freezing on spring dead spot severity in bermudagrass HortScience 40 421 423 https://doi.org/10.21273/HORTSCI.40.2.421
Kaminski, J.E. & Dernoeden, P.H. 2005 Nitrogen source impact on dead spot (Ophiosphaerella agrostis) recovery in creeping bentgrass Int. Turfgrass Soc. Res. J. 10 214 223
Krogmeier, M.J., McCarty, G.W. & Bremner, J.M. 1989 Phytotoxicity of foliar-applied urea Proc. Natl. Acad. Sci. USA 86 8189 8191 https://doi.org/10.1073/pnas.86.21.8189
Martin, D.L., Taliaferro, C.M., Tisserat, N.A., Bell, G.E., Baird, J.H., Dobson, D.D., Anderson, J.A. & Kuzmic, R.M. 2001 Hardy bermudagrass sought with resistance to spring dead spot Golf Course Manage. June 75 79
Martinez, J.F.I., Flores, F.J., Koch, A.R., Garzon, C.D. & Walker, N.R. 2019 Multiplex end-point PCR for the detection of three species of Ophiosphaerella causing spring dead spot of bermudagrass Plant Dis. 103 2010 2014 https://doi.org/10.1094/PDIS-10-18-1727-RE
Martinez, A., Workman, J.B. & Waltz, F.C. 2014 Identification and control of spring dead spot in Georgia UGA Extension Circular 1012
McCarty, L.B., Lucas, L.T. & DiPaola, J.M. 1992 Spring dead spot occurrence in bermudagrass following fungicide and nutrient applications HortScience 27 10 1092 1093 https://doi.org/10.21273/HORTSCI/27.10.1092
Miller, G.L., Earlywine, D.T. & Fresenburg, B.S. 2017 Effect of fraze mowing on spring dead spot caused by Ophiosphaerella herpotricha of bermudagrass Int. Turfgrass Soc. Res. J. 13 225 228 https://doi.org/10.2134/itsrj2016.10.0839
Perry, D.H., Tomaso-Peterson, M. & Baird, R. 2010 Seasonal variation in frequency of isolation of Ophiosphaerella korrae from bermudagrass roots in Mississippi and pathogenicity and optimal growth of selected isolates Mycopathologia 169 395 402 https://doi.org/10.1007/s11046-010-9273-x
Tisserat, N.A. & Fry, J.D. 1997 Cultural practices to reduce spring dead spot (Ophiosphaerella herpotricha) severity in Cynodon dactylon J. Intl. Turf. Res. 8 931 936
Tisserat, N.A., Hulbert, S.H. & Sauer, K.M. 1994 Selective amplification of rDNA internal transcribed spacer regions to detect Ophiosphaerella korrae and O. herpotricha Phytopathology 84 478 482
Tredway, L.P., Soika, M.D. & Butler, E.L. 2009a Response of spring dead spot caused by Ophiosphaerella korrae and O. herpotricha to fertilization programs and preventative fungicide applications Phytopathology 99 6 S129
Tredway, L.P., Soika, M.D., Butler, E.L. & Kerns, J.P. 2020 Impact of nitrogen source, fall fertilizers, and preventative fungicides on spring dead spot caused by Ophiosphaerella korrae and O. herpotricha Crop Sci. Special Issue: International Turfgrass Research Conference 1 10 https://doi.org/10.1002/csc2.20306
Tredway, L.P., Tomaso-Peterson, M., Perry, H. & Walker, N.R. 2009b Spring dead spot of bermudagrass: A challenge for researchers and turfgrass managers. Online Plant Health Prog. https://doi.org/10.1094/PHP-2009-0710-01- RV
Venkatasubbaiah, P., Tisserat, N.A. & Chilton, W.S. 1994 Metabolites of Ophiosphaerella herpotricha, a cause of spring dead spot of bermudagrass Mycopathologia 128 155 159 https://doi.org/10.1007/BF01138477
Wadsworth, D.F. & Young, H.C. 1960 Spring dead spot of bermudagrass Plant Dis. 44 516 518
Walker, N.R. 2013 Evaluation of post fungicide application irrigation on control of spring dead spot of bermudagrass in Oklahoma, 2012-2013 Plant Dis. Manag. Rep. 8 T011
