Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Field research demonstrated that calcium nitrate fertilizer effectively controlled Ophiosphaerella korrae, one causal agent of spring dead spot, whereas the other causal agent, O. herpotricha, we suppressed by ammonium sulfate. We have developed two new techniques for assessment of spring dead spot severity in the field: aerial photography in combination with GIS analysis and reflectance-based mapping of the turf with a GPS-linked sensor mounted on a cart or mower. These methods will be used to assess treatment performance in large plot studies on golf courses and athletic fields. Field experiments were continued throughout North Carolina to determine the most common causes of fairy ring and develop effective strategies for its management. Multi-locus sequence data and mycelial compatibility groups were determined for a global subsample of Sclerotinia homoeocarpa populations. Results show that populations from warm-season grasses are subdivided from those from cool-season grasses. We have cloned and sequenced the CYP51 gene, which controls sensitivity to the DMI fungicides in most fungi. However, after sequencing this gene in a range of resistance and sensitive isolates, it is apparent that point mutations in CYP51 are not related to DMI sensitivity in S. homoeocarpa. PARTICIPANTS: Research was performed by myself, M.D. Soika, E.L. Butler, and B. Ma. Funding was provided by the Carolinas Golf Course Superintendents Association, the North Carolina Turfgrass Foundation, the NC State Turfgrass Center, the Golf Course Superintendents Association of America, and Bayer Environmental Science. TARGET AUDIENCES: The target audience is turfgrass managers and other turfgrass scientists. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
We have determined that certain nitrogen sources can provide effective suppression of spring dead spot in bermudagrass, opening new options to turfgrass managers dealing with this destructive disease. In addition, we have identified certain fungicide programs that provide effective control of both causal agents of this disease. Through this research, truly integrated management programs have been developed for this destructive bermudagrass disease. The majority of fairy ring pathogens in sand-based golf course putting greens are puffball fungi in the Lycoperdon, Vascellum, and Bovista genera, whereas mushroom fungi in the genera Marasmius and Coprinus have been more common in soil-based greens. We have developed rapid and specific methods for identification of the most common species from infested soils, negating the need for fruiting bodies to make an accurate identification. Effective and specific prevention programs have been developed and are being employed by the majority of golf course supertintendents in North Carolina. As a result, we have heard few reports of fairy ring problems over the last two years. Data collected to date shows that little diversity exists in Sclerotinia homoeocarpa populations from cool-season grasses, whereas considerable diversity has been detected in warm-season populations. In addition, we have detected no overlap in the populations associated with these different grass types, suggesting that strains of this pathogen are host-specific. Sclerotinia homoeocarpa apparently does not utilize the same DMI resistance mechanism as most other fungi. More research is needed to reveal the mechanisms that are responsible for DMI resistance in this pathogen so that we can develop methods to prevent its development.
Publications
- Miller, G. L. and L. P. Tredway 2009. "Impact of application method on the efficacy of preventive DMI fungicide applications for fairy ring control on golf putting greens." Phytopathology 99: S86-S86. Miller, G. L. and L. P. Tredway. "Optimal timing of preventative fungicide applications for fairy ring caused by Vascellum pratense in creeping bentgrass putting greens." Phytopathology 99: S199-S199. Taylor, T. A., I. Carbone, et al. "Multilocus sequence analysis of Sclerotinia homoeocarpa populations from turfgrasses." Phytopathology 99: S127-S127. Taylor, T. A., I. Carbone, et al. 2009. "Genetic structure of Sclerotinia homoeocarpa populations from turfgrasses in North America, Asia and Europe." Phytopathology 99: S201-S201. Tredway, L. P., M. D. Soika, et al. 2009. "Response of spring dead spot caused by Ophiosphaerella korrae and O. herpotricha to fertilization programs and preventive fungicide applications." Phytopathology 99:S129-S129. Tredway, L. P., G. G. Wilkerson, et al. 2009. "TurfFiles decision aids for diagnosis and management of turfgrass diseases." Phytopathology 99: S129-S129. Crouch, J. A., L. P. Tredway, et al. 2009. "Phylogenetic and population genetic divergence correspond with habitat for the pathogen Colletotrichum cereale and allied taxa across diverse grass communities." Molecular Ecology 18:123-135. Kerns, J. P., M. D. Soika, et al. 2009. "Preventive control of Pythium root dysfunction in creeping bentgrass putting greens and sensitivity of Pythium volutum to fungicides " Plant Disease 93: 1275-1280.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Field experiments were continued to compare the aggressiveness of Ophiosphaerella species toward bermudagrass and evaluate their differential response to management practices. We are collaborating with agricultural engineers to develop scanning and spray equipment to map and treat spring dead spot in bermudagrass using GPS technology. A mapping unit has been built and testing in the shop, and will be tested extensively in the field this spring when spring dead spot symptoms are evident. Field experiments were conducted throughout North Carolina to determine the most common causes of fairy ring and develop effective strategies for its management. Populations of Sclerotinia homoeocarpa were sampled in North Carolina, Connecticut, New Jersey, Oklahoma, Mississippi, Italy, Chile, and the United Kingdom. Multi-locus sequence data and mycelial compatibility groups are being determined for all of these isolates. Results of this research have been distributed to stakeholders through trade publications, refereed journal articles, websites (primarily www.turffiles.ncsu.edu) and conference presentations. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Turfgrass managers, and those that provide support to turfgrass managers (consultants, extension personnel, sales representatives) are the target audiences for our research results. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Ophiosphaerella herpotricha was more aggressive than O. korrae in inoculated field plots, with the primary difference between the two being the diameter of spring dead spot patches. Despite this difference in aggressiveness, both species are controlled effectively by preventative application of the fungicide fenarimol and by fertilization with ammonium sulfate as the sole nitrogen source. Through this research, management programs have been developed that are effective against the most common caused of spring dead spot in North Carolina. The majority of fairy ring pathogens in sand-based golf course putting greens are puffball fungi in the Lycoperdon, Vascellum, and Bovista genera, whereas mushroom fungi in the genera Marasmius and Coprinus have been more common in soil-based greens. Effective and specific prevention programs have been developed and are being employed by the majority of golf course supertintendents in North Carolina. As a result, we have heard few reports of fairy ring problems over the last year. Data collected to date shows that little diversity exists in Sclerotinia homoeocarpa populations from cool-season grasses, whereas considerable diversity has been detected in warm-season populations. In addition, we have detected no overlap in the populations associated with these different grass types, suggesting that strains of this pathogen are host-specific.
Publications
- Tredway, L.P. G.L. Miller, E.L. Butler, and M.D. Soika. Distribution of fungicide resistance in North Carolina populations of Sclerotinia homoeocarpa. Plant Disease. In preparation. Kerns, J.P. and L.P. Tredway. 2008. Pathogenicity of Pythium species associated with Pythium root dysfunction of creeping bentgrass and their impact on root growth and survival. Plant Disease. In press. Tredway, L. P., Butler, E. L., Soika, M. D., and Bunting, M. L. 2007. Etiology and management of spring dead spot of hybrid bermudagrass in North Carolina, USA. Acta Horticulturae In press. Roberts, J. A., and Tredway, L. P. 2008. First report of Curvularia blight of zoysiagrass caused by Curvularia lunata in the United States. Plant Disease 92:173. Dong, S., Shew, H. D., Tredway, L. P., Lu, J., Sivamani, E., and Qu, R. 2008. Expression of the bacteriophage T4 lysozyme gene in tall fescue confers resistance to gray leaf spot and brown patch diseases. Transgenic Research 17:47-57. Tredway, L. P., and Butler, E. L. 2007. First report of spring dead spot of zoysiagrass caused by Ophiosphaerella korrae in the United States. Plant Disease 91:1684. Dong, S., Tredway, L. P., Shew, H. D., Wang, G. L., Sivamani, E., and Qu, R. 2007. Resistance of transgenic tall fescue to two major fungal diseases. Plant Science 173:501-509. Kerns, J. P., and Tredway, L. P. 2007. First report of Pythium root dysfunction of creeping bentgrass caused by Pythium volutum in North Carolina. Plant Disease 91:632. Carley, D. S., Cappy, J., Tredway, L. P., and T.W.Rufty. 2007. Heat and nutritional interactions in bentgrass. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA. Dong, S., Tredway, L. P., Shew, H. D., Lu, J., Sivamani, E., Miller, E., and Qu, R. 2007. Resistance of transgenic tall fescues to gray leaf spot and brown patch diseases. Phytopathology 97:S29. Kerns, J. P., and Tredway, L. P. 2007. Determination of the optimal temperature range for infection of creeping bentgrass by Pythium volutum, a causal agent of Pythium root dysfunction. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA. Kerns, J. P., and Tredway, L. P. 2007. Effects of soil organic matter content and irrigation frequency on the severity of Pythium root dysfunction. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA. Kerns, J. P., and Tredway, L. P. 2007. Effects of temperature on infection of creeping bentgrass roots by Pythium volutum. Phytopathology 97:S59. Kerns, J. P., and Tredway, L. P. 2007. Characterization and pathogenicity of Pythium species associated with Pythium root dysfunction in North Carolina. Phytopathology 97:S59. Miller, G. L., Soika, M. D., and Tredway, L. P. 2007. Preventative control of fairy ring associated with Lycoperdon perlatum in creeping bentgrass. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA. Miller, G. L., Soika, M. D., and Tredway, L. P. 2007. Preventative control of fairy ring caused by Lycoperdon perlatum. Phytopathology 97:S77. Miller, G. L., and Tredway, L. P. 2007. Isolation and identification of the basidiomycete fungi causing fairy rings in golf course putting greens. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA. Miller, G. L., and Tredway, L. P. 2007. Isolation and identification of the basidiomycete fungi causing fairy rings in golf course putting greens. Phytopathology 97:S77.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: Research results and resulting management recommendations are disseminated to turfgrass managers and extension personnel in a variety of formats, including conference presentations, workshops, seminars, trade journal publications, and newsletters. In addition, information is incorporated into NC State's Turfgrass Program Website, www.turffiles.ncsu.edu as news items, information notes, and decision aids.
TARGET AUDIENCES: Turfgrass managers, and those that provide support to turfgrass managers (consultants, extension personnel, sales representatives) are the target audiences for our research results.
Impacts
Research of the etiology of turfgrass diseases has resulted in the description and documentation of three new turfgrass diseases: Pythium root dysfunction of creeping bentgrass, caused by Pythium volutum, spring dead spot of zoysiagrass caused by Ophiosphaerella korrae, and Curvularia blight of zoysiagrass caused by Curvularia lunata. We documented that these fungi are capable of inducing the disease in growth chamber and field experiments, and developed procedures for accurate diagnosis of these problems. Through a series of field experiments, effective management programs have been developed for each diseases. The impact of Pythium volutum infections on creeping bentgrass root function is being investigated. Data gathered in 2007 show that infected roots, once exposed to high temperatures, exhibit increased nitrate assimilation and water uptake in the first 48 to 72 hours. This is followed by a rapid decline in root function, which ultimately leads to dieback of the
foliage. We have begun to research the etiology and management of fairy rings in golf course putting greens in the United States. Previously, the most widespread cause of fairy ring in golf course putting greens was thought to be Lycoperdon perlatum, however, we have not isolated this species to date. Instead, we have found that two different puffball species, Lycoperdon pusilum and Vascellum pratense, are most widely distributed. We have developed effective and economical programs for preventative management of these species in creeping bentgrass putting greens.
Publications
- Dong, S., L.P. Tredway, H.D. Shew, J. Lu, E. Sivamani, E. Miller, and R. Qu. 2007. Resistance of transgenic tall fescues to gray leaf spot and brown patch diseases. Phytopathology. 97:S29.
- Kerns, J.P. and L.P. Tredway. 2007. Determination of the optimal temperature range for infection of creeping bentgrass by Pythium volutum, a causal agent of Pythium root dysfunction. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA.
- Kerns, J.P. and L.P. Tredway. 2007. Effects of soil organic matter content and irrigation frequency on the severity of Pythium root dysfunction. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA.
- Roberts, J.A. and L.P. Tredway. 2007. First Report of Curvularia Blight of Zoysiagrass Caused by Curvularia lunata in the United States. Plant Disease. In press.
- Tredway, L.P. and E.L. Butler. 2007. First report of spring dead spot of zoysiagrass caused by Ophiosphaerella korrae in the United States. Plant Disease. In press.
- Tredway, L.P., E.L. Butler, M.D. Soika, and M.L. Bunting. 2007. Etiology and management of spring dead spot of hybrid bermudagrass in North Carolina, USA. Acta Horticulturae. In press.
- Dong, S., L.P. Tredway, H.D. Shew, G.L. Wang, E. Sivamani, R.Qu. 2007. Resistance of transgenic tall fescue to two major fungal diseases. Plant Science. doi:10.1016/j.plantsci.2007.08.002.
- Dong, S., H.D. Shew, L.P. Tredway, J. Lu, E. Sivamani, and R. Qu. 2007. Expression of the bacteriophage T4 lysozyme gene in tall fescue confers resistance to gray leaf spot and brown patch diseases. Transgenic Research. 16:1-11. doi:10.1007/s11248-007-9073-3.
- Kerns, J.P. and L.P. Tredway. 2007. First report of Pythium root dysfunction of creeping bentgrass caused by Pythium volutum in North Carolina. Plant Disease. 91:632.
- Carley, D.S., J. Cappy, LP. Tredway, and T.W.Rufty. 2007. Heat and nutritional interactions in bentgrass. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA.
- Kerns, J.P. and L.P. Tredway. 2007. Effects of temperature on infection of creeping bentgrass roots by Pythium volutum. Phytopathology. 97:S59.
- Kerns, J.P. and L.P. Tredway. 2007. Characterization and pathogenicity of Pythium species associated with Pythium root dysfunction in North Carolina. 97:S59.
- Miller, G.L., M.D. Soika, and L.P. Tredway. 2007. Preventative control of fairy ring associated with Lycoperdon perlatum in creeping bentgrass. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA.
- Miller, G.L. and L.P. Tredway. 2007. Isolation and identification of the basidiomycete fungi causing fairy rings in golf course putting greens. ASA-CSSA-SSSA International Annual Meetings, New Orleans, LA.
- Miller, G.L. and L.P. Tredway. 2007. Isolation and identification of the basidiomycete fungi causing fairy rings in golf course putting greens. Phytopathology. 97:S77.
- Miller, G.L., M.D. Soika, and L.P. Tredway. 2007. Preventative control of fairy ring caused by Lycoperdon perlatum. Phytopathology. 97:S77.
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Progress 10/01/04 to 09/30/05
Outputs
Experiments were repeated to evaluate fungicides and application methods for spring dead spot control in bermudagrass turf. As in previous years, fungicides containing fenarimol and propiconazole were most effective in controlling spring dead spot, and application methods that delivered the fungicide to the soil were more effective than foliar applications. An additional field experiment was initiated to optimize the rate and timing of fenarimol applications for spring dead spot control. Applications were equally effective when made between mid-August and late October, corresponding to soil temperatures between 60F and 80F. No significant differences were detected among application rates of 6, 8, or 12 fluid ounces per 1000 square feet. Studies of spring dead spot etiology were continued, and isolates of Ophiosphaerella spp. were speciated using PCR-based assays and morphological characteristics. O. korrae is the dominant pathogen causing spring dead spot in North
Carolina, but O. herpotricha is present in certain locations in all regions of North Carolina.A real-time PCR assay for monitoring Ophiosphaerella growth in soil samples is currently under development, which will enable us to develop accurate and specific epidemiological models for spring dead spot development. Field plots were inoculated with strains of Sclerotinia homoeocarpa, the causal agent of dollar spot, with varying sensitivity to the DMI fungicide propiconazole. Fungicide treatments were applied to the inoculated plots to evaluate their curative effect on the different populations. DMI fungicides and fungicides in other chemical classes were less effective in populations with propiconazole ED50s of 0.002, 0.033, and 0.054 than in a wild-type population with an ED50 of 0.011. Significant progress has been made in the characterization of creeping bentgrass root diseases. In addition to our documenting Magnaporthe poae as a creeping bentgrass pathogen, we are also characterizing
a previously unknown disease called Pythium root dysfunction caused by Pythium volutum. Effective fungicide programs for control of Pythium root dysfunction have been developed based on a series of field trials conducted throughout North Carolina. Greenhouse experiments to determine the effect of soil type and soil temperature on Pythium volutum development are underway. Field trials were conducted in 2004 and 2005 to evaluate reduced rates of fungicides for brown patch control in susceptible and moderately resistant varieties of tall fescue. Overall, reduced rates of fungicides provided acceptable control on the moderately resistant variety Endeavor but not on the susceptible cultivar Coronado.
Impacts
This research has provided key pieces of information regarding the biology and management of turfgrass diseases in the Southeastern United States. Results from spring dead spot management research have enabled us to develop more specific and effective recommendations for control of the most destructive disease of bermudagrass in the southeastern United States. For dollar spot control, reductions in DMI efficacy occur at much lower ED50 values than was previously thought when these fungicides are applied on a curative basis. Reduced propiconazole sensitivity may also impact the efficacy of other fungicide chemistries. These results explain the difficulties that turf managers experience when attempting to manage these populations and highlight the importance of preventative management of dollar spot. The further characterization of creeping bentgrass root diseases has improved our ability to accurately diagnose disease problems in golf course putting greens and develop
effective management programs for management of golf course putting greens. Identification of fungicide treatments for brown patch in tall fescue that are safe and cost-effective will significantly improve the quality of tall fescue landscapes while reducing economic losses in the landscape industry and minimizing negative impacts on environmental quality. The use of moderately resistant cultivars, such as Endeavor, permits additional reductions in fungicide application rates, further maximizing safety and cost efficiency.
Publications
- Tredway, L.P. 2005. First report of summer patch of creeping bentgrass caused by Magnaporthe poae in North Carolina. Plant Disease 89:204.
- Butler, E.L. and L.P. Tredway. 2005. Comparison of methods for evaluation of spring dead spot incidence in hybrid bermudagrass. International Turfgrass Society Research Journal. 10:273-280.
- Reynolds, W.C., E.L. Butler, H.C. Wetzel, A.H. Bruneau, and L.P. Tredway. 2005. Performance of Kentucky bluegrass-tall fescue mixtures in the Southeastern United States. International Turfgrass Society Research Journal. 10:525-530.
- Tredway, L.P., K.L. Stevenson, and L.L. Burpee. 2005. Genetic structure of Magnaporthe grisea populations associated with turfgrass hosts in Georgia. Phytopathology. 95:463-471.
- Tredway, L.P. and E.L. Butler. 2005. Development of effective fungicide programs for spring dead spot control in hybrid bermudagrass. Phytopathology. 95:S104.
- Tredway, L.P. 2005. Sensitivity to benzimidazole, dicarboxamide, and DMI fungicides in North Carolina populations of Sclerotinia homoeocarpa. Phytopathology. 95:S104.
- Kerns, J.P. and L.P. Tredway. 2005. Pythium species associated with root dysfunction of creeping bentgrass in North Carolina. Phytopathology. 95:S202.
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Progress 10/01/03 to 09/30/04
Outputs
Methods for spring dead spot control in bermudagrass turf were evaluated for a second year in field experiments. Fungicides containing fenarimol and propiconazole were most effective in controlling spring dead spot. Application methods that delivered the fungicide to the soil were more effective than foliar applications. Fungicide applications were most effective when made in the fall when average soil temperature was between 60F and 80F. Studies of spring dead spot etiology have demonstrated that Ophiosphaerella korrae is the predominant pathogen in North Carolina, however, O. herpotricha has been identified in several locations. Field plots have been inoculated with each of these pathogens to determine if they differ in their aggressiveness or respond differently to spring dead spot control practices. We are currently developing a real-time PCR method for quantification of spring dead spot pathogen activity. This method will facilitate the development of an
epidemiological model for spring dead spot which could be used by turfgrass managers to time fungicide applications or other management practices. Over 600 isolates of Sclerotinia homoeocarpa were collected from golf course putting greens in North Carolina and were analyzed for resistance to common fungicides. All isolates tested were completely resistant to thiophanate-methyl. Most isolates were sensitive to iprodione, but a low frequency of moderate resistance to this fungicide was detected in two locations. A wide range of sensitivities to propiconazole were observed in populations, with mean relative growth values ranging from 0.47 to 0.87. Based on these results, fungicide resistance is not widespread in S. homoeocarpa populations in North Carolina. Difficulties in dollar spot control reported by turfgrass managers may be a result of varietal susceptibility, cultural factors, or fungicide application methods rather than fungicide resistance. Significant progress has been made in
the characterization of two previously unknown diseases in creeping bentgrass putting greens. One of these diseases is caused by Magnaporthe poae and has been named summer patch. Kochs postulates have been completed with this fungus in the growth chamber and in the field in two locations. This represents an expansion of the known host range of M. poae, which had previously been associated only with bluegrass and fescue species. A second disease of creeping bentgrass putting greens remains unknown, but evidence collected to date indicates that this is a root dysfunction disease caused by a species of Pythium. In 2004, potential pathogens were isolated from creeping bentgrass in NC, GA, SC, and VA exhibiting symptoms of this disease. Of 45 Pythium isolates collected, 36 have been identified as P. volutum and 9 have been identified as P. torulosum. Pythium volutum is known to be highly aggressive to creeping bentgrass seedlings, whereas P. torulosum is weakly virulent or non-pathogenic
to creeping bentgrass seedlings. Growth chamber experiments are underway to characterize the pathogenicity of these fungi to mature creeping bentgrass plants.
Impacts
The results of this research have provided key pieces of information regarding the biology and management of turfgrass diseases in the Southeastern United States. Results from spring dead spot management research have enabled us to develop effective recommendations for control of the most destructive disease of bermudagrass in the southeastern United States. A complete knowledge of the distribution of fungicide resistance in Sclerotinia homoeocarpa populations in North Carolina will enable turfgrass managers to select fungicides for dollar spot control that are likely to be effective in their location. Additional field research will be conducted to develop fungicide tank-mixtures or rotations that are effective for control of the most common resistance types in North Carolina. The characterization of unknown diseases in creeping bentgrass has improved our ability to accurately diagnose disease problems in golf course putting greens and will enable us to develop
effective management programs for this disease.
Publications
- Butler, E.L. and L.P. Tredway. 2004. Development of effective fungicide programs for spring dead spot control in bermudagrass. Agronomy Abstracts. 2004:5264.
- Butler, E.L. and L.P. Tredway. 2004. Distribution of Ophiosphaerella species causing spring dead spot of bermudagrass in North Carolina. Agronomy Abstracts. 2004:5249.
- Butler, E.L. and L.P. Tredway. 2004. Development of effective strategies for control of spring dead spot in bermudagrass. Phytopathology. 94:S167.
- Butler, E.L. and L.P. Tredway. 2004. Brown patch control in creeping bentgrass using Serenade AS, 2003. Biological and Cultural Tests for Control of Plant Diseases. 19:T001.
- Butler, E.L. and L.P. Tredway. 2004. Evaluation of Serenade AS for control of dollar spot in creeping bentgrass, 2003. Biological and Cultural Tests for Control of Plant Diseases. 19:T002.
- Butler, E.L. and L.P. Tredway. 2004. Preventative control of brown patch and dollar spot in creeping bentgrass putting greens, 2003. Fungicide and Nematicide Tests. 59:T023.
- Butler, E.L. and L.P. Tredway. 2004. Preventative control of spring dead spot in bermudagrass putting greens, 2002-2003. Fungicide and Nematicide Tests. 59:T026.
- Tredway, L.P. and E.L. Butler. 2004. Evaluation of fungicides for control of dollar spot in creeping bentgrass, 2003. Fungicide and Nematicide Tests. 59:T022.
- Tredway, L.P. and E.L. Butler. 2004. Evaluation of fungicides for maintenance of summer quality in creeping bentgrass, 2003. Fungicide and Nematicide Tests. 59:T024.
- Tredway, L.P. and E.L. Butler. 2004. Evaluation of Chipco Signature tank-mix partners for maintenance of summer quality in creeping bentgrass, 2003. Fungicide and Nematicide Tests. 59:T025.
- Tredway, L.P. and E.L. Butler. 2004. Control of brown patch in tall fescue with monthly fungicide applications in Raleigh, NC, 2003. Fungicide and Nematicide Tests. 59:T030.
- Butler, E.L. and L.P. Tredway. 2004. Preventative control of spring dead spot in bermudagrass athletic fields, 2002-2003. Fungicide and Nematicide Tests. 59:T027.
- Gregg, J.P., C.H. Peacock, H.D. Shew, and L.P. Tredway. 2004. Herbicide and nutrient effects on the development of gray leaf spot of tall fescue. Agronomy Abstracts. 2004:3953.
- Lee, D.J., L.P. Tredway, H.D. Shew, and C.H. Peacock. 2004. Structure and dynamics of Rhizoctonia populations in creeping bentgrass in response to fungicide programs. Phytopathology. 94:S58.
- Tredway, L.P. 2004. Summer patch of creeping bentgrass caused by Magnaporthe poae in North Carolina. Phytopathology. 94:S103.
- Tredway, L.P. and E.L. Butler. 2004. Curative control of algae invasion in creeping bentgrass, 2003. Fungicide and Nematicide Tests. 59:T021.
- Tredway, L.P. and J.H. Monroe. 2004. Control of brown patch in tall fescue with monthly fungicide applications in Charlotte, NC, 2003. Fungicide and Nematicide Tests. 59:T029.
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Progress 10/01/02 to 09/30/03
Outputs
Methods for spring dead spot control in bermudagrass turf were evaluated. Experiments were designed to evaluate the effects of product selection, application timing, and application method on spring dead spot control. Fungicides containing fenarimol and propiconazole were most effective in controlling spring dead spot. Application methods that delivered the fungicide to the soil were more effective than foliar applications. Fungicide applications were most effective when made in the fall when average soil temperature was between 60F and 80F. Certain fungicides slowed bermudagrass recovery from spring dead spot injury in the spring. Studies of spring dead spot etiology were initiated by collecting samples of bermudagrass exhibiting disease symptoms. Several hundred isolates of Ophiosphaerella spp. were obtained from these samples, and are currently being identified to species using PCR-based assays and DNA sequencing. Core samples of bermudagrass turf were also
collected on a monthly basis from August to November for epidemiological studies. The samples are being analyzed with real-time PCR in order to develop an epidemiological model for spring dead spot development based on soil temperature. Nearly 400 isolates of Sclerotinia homoeocarpa were collected from golf course putting greens in North Carolina, and are being analyzed for resistance to common fungicides. Most isolates tested were completely resistant to thiophanate-methyl. Most isolates were completely sensitive to iprodione, but a low frequency of moderately resistance to this fungicide was detected in two locations. A wide range of sensitivities to propiconazole were observed in populations, with relative growth values ranging from 0.33 to 0.80. The sensitivity of these isolates to additional fungicides are being analyzed currently. Epidemiological models were evaluated for their ability to predict brown patch development in creeping bentgrass. The Fidanza model was most
effective, but correctly predicted disease development only 50% of the time. Most false negatives occurred when the previous days high temperature was greater than 30C, and most false positives occurred when heavy rainfall occurred during the night. A more accurate disease prediction model may be developed by taking these factors into account. Significant progress has been made in the characterization of an unknown disease in creeping bentgrass putting greens. A fungus has been consistently isolated from samples of creeping bentgrass, and this fungus has been identified as a species of Magnaporthe. Kochs postulates have been completed with this fungus in the growth chamber and in the field in two locations. Field trials were established in summer 2003 in Mecklenburg and Wake Cos. to evaluate fungicides for control of brown patch in tall fescue landscapes. Three fungicides provided excellent control of brown patch in both locations when applied on 4 week intervals: Prostar (3 oz),
Systar (3 oz), and Heritage (0.2 oz). Of these treatments, Heritage is most cost-effective and is similar in price to several less-effective products that are widely used in the landscape management industry.
Impacts
The results of this research have provided key pieces of information regarding the biology and management of turfgrass diseases in the Southeastern United States. Results obtained from spring dead spot management research have enabled us to develop effective recommendations for control of the most destructive disease of bermudagrass in the southeastern United States. Additional information provided by studies of spring dead spot etiology and epidemiology will help to make recommendations more site-specific. A complete knowledge of the distribution of fungicide resistance in Sclerotinia homoeocarpa populations in North Carolina will enable turfgrass managers to select fungicides for dollar spot control that are likely to be effective in their location. Additional field research will be conducted to develop fungicide tank-mixtures or rotations that are effective for control of the most common resistance types in North Carolina. The characterization of an unknown disease
in creeping bentgrass has improved our ability to accurately diagnose disease problems in golf course putting greens and will enable us to develop effective management programs for this disease. Identification of fungicide treatments for brown patch in tall fescue that are safe and cost-effective will significantly improve the quality of tall fescue landscapes while reducing economic losses in the landscape industry and minimizing negative impacts on environmental quality.
Publications
- Abad, Z.G., Abad, J.A., and Tredway, L.P. 2003. Characterization of a new subgroup of Rhizoctonia solani AG 2-2 associated with creeping bentgrass in North Carolina. Phytopathology 93:S1.
- Burpee, L.L., Mims, C.W., Tredway, L.P. and Jung, G. 2003. Pathogenicity of a novel biotype of Limonomyces roseipellis in tall fescue. Plant Disease. 87:1031-1036.
- Tredway, L.P. and Butler, E.L. 2003. Evaluation of fungicides for maintenance of turfgrass quality and control of brown patch and algae, 2002. Fungicide and Nematicide Tests. 58:T005.
- Tredway, L.P. and Butler, E.L. 2003. Evaluation of fungicides for curative control of brown patch, 2002. Fungicide and Nematicide Tests. 58:T006.
- Tredway, L.P. and Butler, E.L. 2003. Control of brown patch and algae in creeping bentgrass in North Carolina, 2002. Fungicide and Nematicide Tests. 58:T018.
- Tredway, L.P., Stevenson, K.L. and Burpee, L.L. 2003. Mating type distribution and fertility status in Magnaporthe grisea populations associated with turfgrass hosts in Georgia. Plant Disease. 87:435-441.
- Tredway, L.P., Stevenson, K.L. and Burpee, L.L. 2003. Components of resistance to Magnaporthe grisea in Coyote and Coronado tall fescue. Plant Disease. 87:906-912.
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