...Using Science to Benefit Golf

Turfgrass and EnvironmentalResearch Online

Volume 8, Number 22November 15, 2009

Research at Clemson University continues to investigate Rhizoctonia leaf and sheath spoton bermudagrass. In recent years in South Carolina, North Carolina, Georgia, Mississippi,Alabama, Louisiana and Texas symptoms have been observed on bermudagrass puttinggreens. Shown above are typical field symptoms of Rhizoctonia leaf and sheath spot onbermudagrass putting greens where patches and rings typically are about 6 inches up to 2feet in diameter.

PURPOSE

The purpose of USGA Turfgrass and Environmental Research Online is to effectively communicate the results ofresearch projects funded under USGA’s Turfgrass and Environmental Research Program to all who can benefitfrom such knowledge. Since 1983, the USGA has funded more than 400 projects at a cost of $34 million. The pri-vate, non-profit research program provides funding opportunities to university faculty interested in working on envi-ronmental and turf management problems affecting golf courses. The outstanding playing conditions of today’sgolf courses are a direct result of using science to benefit golf.

Editor

Jeff Nus, Ph.D.1032 Rogers PlaceLawrence, KS 66049jnus@usga.org(785) 832-2300(785) 832-9265 (fax)

Research Director

Michael P. Kenna, Ph.D.P.O. Box 2227Stillwater, OK 74076mkenna@usga.org(405) 743-3900(405) 743-3910 (fax)

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USGA Turfgrass and Environmental Research Committee

Steve Smyers, Co-chairmanGene McClure, Co-chairman

Julie Dionne, Ph.D.Ron Dodson

Kimberly Erusha, Ph.D.Pete Grass, CGCSAli Harivandi, Ph.D.

Michael P. Kenna, Ph.D.Jeff Krans, Ph.D.

James MooreJeff Nus, Ph.D.

Paul Rieke, Ph.D.James T. Snow

Clark Throssell, Ph.D.Ned Tisserat, Ph.D.Scott Warnke, Ph.D.

James Watson, Ph.D.Chris Williamson, Ph.D.

There is no more interesting group ofpathogens of plants than those in the genusRhizoctonia. This group of fungi, as they say, is"older than dirt" and the best known representa-tives among Rhizoctonia solani were describedoriginally and coincident with the dawn of the dis-cipline of plant pathology. In order to understandmodern terminology and the context of turf dis-eases caused by different Rhizoctonia, including'leaf and sheath spot' and related diseases, we needto review a bit of history.

Rhizoctonia solani was first described byKühn in 1858 as a pathogen of potato (Solanumtuberosum), and since then has continued to be themost studied species group within the genus. Weknow now as a result of volumes of research, thatRhizoctonia solani is actually a group of separateand distinct biological species which we identifyas sub-specific groups.

In turfgrass, the disease ‘large brown

patch’ was first observed on a bentgrass puttinggreen in a golf course near Philadelphia, PA in1913. But it was not until experiments were con-ducted in 1917 by C. V. Piper and H. S. Coe thatthe suspected causal agent was consistently isolat-ed from 'large brown patch' in a red fescue turfgarden in Philadelphia, PA. and identified as R.solani. Members of the species group R. solaniaffect all of the major warm- and cool-season turfspecies. But, what are the characteristics of thegenus Rhizoctonia?

Most fungi produce spores that are theresult of sexual or asexual reproduction, but mem-bers of Rhizoctonia do not produce a spore in theasexual form. They are composed of mycelia andsclerotia only in the asexual state, so characteris-tics are few that can be used taxonomically.

Identification, Pathogenicity, and Control of RhizoctoniaLeaf and Sheath Spot of Bermudagrass Putting Greens.

Bruce Martin

SUMMARY

Research at Clemson University continues to investigateRhizoctonia leaf and sheath spot on bermudagrass. Theirobservations include:

Rhizoctonia leaf and sheath spot has increased in fre-quency and importance on bermudagrass putting greens.

Fungi identified as Rhizoctonia zeae have most consis-tently been associated with symptoms of the disease,although related fungi such as R. oryzae and R. circinatavar. circinata may also be involved.

Curative control with fungicides or masking of symp-toms with fertilizers has been largely ineffective.

Early curative control or preventive control with sever-al fungicides with good efficacy against Rhizoctonia dis-eases has been successful.

BRUCE MARTIN, Ph.D., Interim Director, Pee Dee Research andEducation Center, Department of Entommology and PlantSciences, Clemson University, Florence, SC.

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Typical mycelia characteristics of Rhizoctonia fungi asviewed through the microscope. No spores or clamp con-nections are produced. Secondary hyphae tend to emergefrom primary runner hyphae at right-angle branches, andsepta are formed in secondary hyphae near the point of ori-gin of the secondary branch. These characteristics only pro-vide some information to tentatively place the fungus in thegenus Rhizoctonia.

USGA Turfgrass and Environmental Research Online 8(22):1-10.TGIF Record Number: 157568

Some of the characteristics that place asterile fungus into Rhizoctonia include: lack ofspores, septate hyphal strands, lack of clamp con-nections (a microscopically visible bridge acrosssepta in hypha present in mushroom fungi), andsclerotia of varying form and organization. Notmuch to go on, so it's no wonder many fungi pre-viously described as species of Rhizoctonia arenot related at all. Many, however, were shown tobelong to the Basidiomycete class of true fungi(which includes mushroom fungi, puffballs, andjelly fungi, as well as rusts and smuts) and that iswhere 'true' Rhizoctonia are presently placed taxonomically.

To be placed in the 'species' R. solani, thefungi posses the following characteristics:mycelia are tan to brown color, with right-angledbranching (although young hyphae can produceacute angular branching), septa near the origin ofhyphal branching, constriction of hyphal branchesnear their origin, multinucleate hyphal cells, andformation of dolipore septa. Conidia, clamp con-nections, and rhizomorphs are absent, and sclero-tia are not differentiated into a rind and medulla(like an orange). Rhizoctonia solani fungi have arapid growth rate and pathogenicity may or maynot be present.

Different forms of R. solani have beenidentified based on physiological and genetic dif-ferences that determine host range, pathogenicity,ecological niche, etc. We refer to ‘AG’ whichstands for 'anastomosis group' followed by num-bers and letters to identify specific forms. In turf,at least 4 AGs have been identified, with specificsubgroups beyond AG. These are: AG 1, AG 2,AG 4, and AG 5. To be more specific, R. solaniAG 1, 1A is a major cause of brown patch in tallfescue and perennial ryegrass. It also causes amajor disease of rice, called 'sheath blight'. AG 2-2IIIB is also found on tall fescue and ryegrass, butis the most frequently identified form on creepingbentgrass, causing brown patch.

Another subgroup of AG 2, is R. solaniAG 2-2 LP, which causes large patch disease onwarm-season grasses. We now distinguish the dis-eases and pathogen associations as 'brown patch'on cool-season turf and 'large patch' on warm-sea-son turf. These are distinct diseases with distinctcausal agents. AG 4 isolates are occasionally iso-lated, and are typically found on juvenile turfcausing damping off, or seedling disease. AG 5isolates have been infrequently isolated from tallfescue and other grasses, but are not major turfpathogens as far as we know now.

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Typical field symptoms of Rhizoctonia leaf and sheath spot on bermudagrass putting greens. Patches and rings typically areabout 6 inches up to 2 feet in diameter.

Other Rhizoctonia

From the original identification of R.solani on red fescue in the 1920s until the mid-1970s, R. solani was the only fungus associatedwith turf diseases, which were called 'brownpatch'. In the mid-70s, however, severalresearchers began to pay attention to 'cool season'brown patch which was shown to be caused by abinucleate species of Rhizoctonia that obviouslywas not R. solani (it is white to buff in color, bin-ucleate, and disease occurs in cold weather). The'cool season' brown patch was observed on bent-grass and Poa, and zoysia originally. Eventually,Lee Burpee (now at the University of Georgia)identified the fungus as R. cerealis, and named thedisease it causes 'yellow patch'.

In the late 1970s and early 1980s, I studiedunder Leon Lucas at NC State and worked to iden-tify specific Rhizoctonia associated with manyturfgrasses. We were the first to associateRhizoctonia zeae with turfgrasses in the UnitedStates, although the fungus had been associatedwith Gramineae since it's original description as acorn pathogen in 1932. We also identified R.oryzae on turf which was identified originally in1938 as a pathogen of rice, and the disease in ricewas called 'leaf and sheath spot' of rice.

Do you begin to see where names comefrom? Rhizoctonia zeae and Rhizoctonia oryzaeare the names given to the asexual state (nospores), but both R. zeae and R. oryzae have beenshown to form a sexual state, which is classifiedas Waitea circinata. It should be noted that thesexual state of turf isolates has not been identifiedin turf in nature and only once in the United Statesin the laboratory by Dr. Alan Windham,University of Tennessee.

Waitea circinata was described by Warcupas a soil-borne fungus and was not associated atthat time as a pathogen of plants (19). Warcupworked at the Waite Agricultural ResearchInstitute near Adelaide, South Australia, hence thename 'Waitea'. In 1979, Christensen identifiedWaitea circinata as a 'Rhizoctonia' disease on tur-fgrasses in New Zealand, but noted that the sexu-al state was not formed with his isolates.

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Typical culture characteristics of Rhizoctonia zeae (A),Rhizoctonia circinata var. circinata (B), and Rhizoctoniaoryzae (C). Cultures may be obtained that overlap acrossthe typical characteristics of color and sclerotial size andmorphology shown here.

A

B

C

Interestingly, he also reported his Waitea circina-ta isolates to be immune to benomyl. A couple ofyears later, our isolates of R. zeae from the UnitedStates were also shown to be immune to benomyl,and after many experiments by others, it is nowaccepted that R. zeae, R. oryzae, and R. circinatavar. circinata are tolerant of benzimidazole fungi-cides, including benomyl and thiophanate methyl.

Getting More Specific with Molecular Biology

In Japan recently, researchers led byTakeshi Toda distinguished fungi causing a 'brownring patch' disease in bentgrass to be caused byWaitea circinata var. circinata. Isolates were dis-tinguished from R. zeae and R. oryzae based onDNA sequences from ribosomal DNA which hasbecome a standard tool to aid in identification offungi and other organisms. In the United States,Dr. Frank Wong, University of California-Riverside has identified similar fungi, identifiedas Rhizoctonia circinata var. circinata, distinctfrom R. zeae and R. oryzae, as a causal agent ofbrown ring patch in Poa annua. Dr. Phil Harmon,University of Florida, has identified R. circinatavar. circinata as a cause of brown ring patch inPoa trivialis overseedings. To be proper and pru-

dent, since the Waitea sexual stage has not beenfound or induced in the lab, the fungus should becalled Rhizoctonia circinata var. circinata, and R.zeae could be called either R. zeae or as proposedby Carling: R. circinata var. zeae, and R. oryzaecould be called R. oryzae or as proposed byCarling: R. circinata var. oryzae. These fungi andthe diseases they cause are related, but appear tobe distinct.

What About Warm-season Grasses?

Much less work has been done with warm-season grasses, except for the important diseasecalled large patch, caused by R. solani AG 2-2 LP,which has been reported on virtually all warm-season grasses. However, outbreaks of a differentdisease on bermudagrass putting greens began tobe more frequent in 2002 up to recent years.Symptoms were distinct rings of a few inches upto greater than a foot in diameter that occurred inspring and fall on non-overseeded putting greens.These symptoms were initially prominent in thesoutheastern United States, gulf coastal region,but have been noted in many locations throughoutthe world on bermudagrass putting greens.

The disease became known as 'mini-ring'

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Figure 1. Curative fungicides applied with and without post-application irrigation. Fungicides were applied on September 18,2007 and again on October 9, 2007. Fungicides were not effective in controlling symptoms curatively.

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and a causal agent was unknown initially.However, symptoms of the disease correspondedexactly with leaf and sheath spot, caused by R.zeae, as described by Dr. Monica Elliott,University of Florida, in the late 1990s onbermudagrass in Florida and identified at aboutthe same time by me in South Carolina. The dis-eases Dr. Elliott identified initially occurred on‘Tifdwarf’bermudagrass.

Leaf and Sheath Spot on Bermudagrass

In recent years in South Carolina, NorthCarolina, Georgia, Mississippi, Alabama,Louisiana, and Texas (and in Argentina andUruguay), similar symptoms have been observedon bermudagrass putting greens. In SouthCarolina, R. zeae is a well-documented pathogenof creeping bentgrass putting greens, causingbrown-patch like symptoms in the heat of sum-mer. It has also been seen frequently causing sim-ilar symptoms to overseedings (primarily Poatrivialis) in fall and spring when temperatures arewarm and humidity is high and prolonged,although R. circinata var. circinata has recentlybeen identified on Poa trivialis in Florida

(Harmon). The fungus has been identified andpathogenicity documented as well on St.Augustinegrass, centipedegrass, and seashore pas-palum (Canegallo and Martin, unpublished). In allcases, the disease has not been controlled withbenzimidazole fungicides, as R. zeae, R. oryzae,and R. circinata var. circinata are essentiallyimmune to that chemistry.

Recent outbreaks have occurred on all ofthe common ultradwarf bermudagrass cultivars onputting greens (‘TifEagle’, ‘Champion’, and‘Mini-Verde’) as well as ‘TifDwarf’ and even‘TifGreen’ in the southeastern United States.Although timing varies, generally the disease isfirst noticed in late August to early fall months. InFlorida, spring symptoms have been described.Initial symptoms are bronze patches of a few inch-es up to a foot or more in diameter. If not con-trolled quickly with fungicides, the pathogenblights and bleaches the lower leaves whichresults in a persistent distinct patch symptom thatis very hard to heal when days are becomingshorter and night temperatures cooler.

This difficulty in healing the disease likelyis more problematic in transition zone climatesthan in more tropical or subtropical environments

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Figure 2. Fertilizer effects on symptoms of Rhizoctonia leaf and sheath spot. Terrain 16-1-2-7 Fe reduced symptoms tem-porarily but effects were not prolonged greater than 2 weeks post application.

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where turf recuperative potential is prolonged.Disease has been known to recur in spring monthsafter turf emerges from dormancy, and presum-ably can detrimentally affect spring transition inoverseeded systems.

Why are these new outbreaks increasing infrequency? Possible reasons include: a) reducedfertility b) nutrient deficiency due to increasedirrigation of sand-based greens planted to shallowrooted ultradwarf bermudagrass cultivars c)increased use of thiophanate methyl in summerfor bermudagrass decline, thereby inducing anincrease in this non-target disease. In severalinstances, 'stress' induced by aggressive verticut-ting has induced severe outbreaks of persistentdisease symptoms. Low nutrition or reduced recu-perative potential by any of the reasons outlinedwould be expected to increase disease severityand prolong healing.

Research at Clemson University hasfocused on the following objectives: 1. Collect isolates of Rhizoctonia from sympto-matic bermudagrass and complete Koch's postu-lates in greenhouse tests. Identify isolates to sub-

group of the Waitea circinata complex .2. Measure disease severity in greenhouse-inocu-lated pots of ‘Champion’ and ‘TifEagle’ bermuda-grass treated with various rates and ratios of N andK. Proposed treatments would be 0.5, 1 and 2 lbN/1000 sq.ft./ 14 days supplemented with 0, 1 or2 lb K in all combinations. Equal amounts of othernutrients would be applied to all treatments.3. Induce the disease in the field.4. In ‘TifEagle’ and ‘Champion’ bermudagrassUSGA putting greens at the Pee Dee Research andEducation Center, determine the influence ofPrimo and thiophanate-methyl and Heritage treat-ments on disease severity in plots treated with twolevels of fertility (0.125 lb N/1000 ft2/ wk and0.25 lb N/1000 ft2/wk).

Results to Date

Many isolates of Rhizoctonia have beencollected from bermudagrass over the past threeyears and fall into the R. circinata complex. Thesefungi have been identified as R. zeae, R.. oryzae,and R. circinata var. circinata. At this time, it has

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Figure 3. Early curative effects of single component fungicides applied 3 times at 2 week intervals, beginning July 15, 2008.Only Heritage TL and Banner Maxx significantly reduced symptoms of severe disease.

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not been determined if one or all can be responsi-ble for the symptoms consistently observed ongolf course bermudagrass putting greens.

In the fall of 2007, the disease occurred onseveral golf courses in South Carolina andthroughout portions of the southeastern UnitedStates. Cultivars were ‘TifEagle’, ‘Champion’,‘TifDwarf’ and in one case, ‘MiniVerde’. Fungimost closely resembling Rhizoctonia zeae or relat-ed fungi were isolated from some samples whenthey were submitted to the lab before treatmentwith fungicides.

In one case, only thiophanate methyl hadbeen used, and Rhizoctonia was easily and readilyisolated from all leaf tissues that were plated. Inmany cases, after multiple fungicides had beenapplied, R. zeae or other potential causal agentscould not be isolated. So, superintendents thatwish to get the best diagnosis of submitted sam-ples are encouraged to simply pull the samplebefore spraying, as a number of broad-spectrumfungicides complicate the isolation and identifica-tion of a purported causal agent.

Identification of R. zeae has been basedpreviously solely on cultural characteristics, basedprimarily on sclerotia size, color, and abundance:R. zeae typically has multiple very small sclerotia(< 1 mm) which are produced both submerged andon culture media surfaces. Rhizoctonia circinatahas been described to have somewhat larger scle-rotia which typically turn brown in culture after afew days. However, these fungi are obviouslyclosely related and cultural characteristics invari-ably will overlap, so final identification and asso-ciation to a variety of R. circinata (zeae, circina-ta, oryzae) depends on separation using DNAtechnology.

Chemical Control Trials

During initiation of this project, severedisease outbreaks in South Carolina made it nec-essary to concentrate on field control of symptomsto develop better recommendations for control.Field trials were initiated on golf courses withsevere disease outbreaks to attempt curative con-

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Figure 4. Early curative effects of fungicides in tank-mix or rotation on Rhizoctonia leaf and sheath spot. Program 2 was: spray1- Heritage + Medallion (1 +0.5 oz), spray 2 - Headway (1.5 oz) and spray 3 - Renown + Medallion (4.5 + 0.5 oz). Program 3was: spray 1 - Heritage TL (1 oz), spray 2 - Medallion (0.5 oz), and spray 3 - Headway (1.5 oz). Programs 2 and 3 were appliedwith or without post-application irrigation at 0.5 inches water.

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trol and provide additional information on fungi-cide efficacy or the influence of fertilizers.

In a separate trial, some fertilizer productsfrom Geoponix company were applied inSeptember and October, 2007 to determine if fer-tilizers could assist in healing or in masking ofsymptoms. In all cases where control was attempt-ed for existing disease that had developed in earlyfall, results were disappointing as symptoms per-sisted throughout the dormancy period, but someslight improvement was noted in one experimentfrom Tartan applications (Figure 1).

In Experiment 2 with fertilizers fromGeoponix, only treatments with Terrain (16-1-2-7Fe) reduced symptoms slightly and temporarily,as might be expected with iron applications(Figure 2). Trials were conducted in lateSeptember when symptoms were already severeand day length and temperatures were not favor-able for bermudagrass growth.

In 2008, trials were initiated to look at pre-ventive treatments of fungicides to determine ifpreventive control was more efficacious (Figure 3and 4). Data shown in Figure 3 represent anothertrial to examine the effects of fungicides withknown efficacy against Rhizoctonia-induced dis-eases. Data shown in Figure 4 represent a simpleexperiment to look at tank-mixes and rotation of 3treatments as 'programs' and determine if post-application irrigation assisted in control.

In these experiments in 2008, even thoughthe first application of fungicides was placed onJuly 15, symptoms had already occurred at asevere level. In Experiment 3, only Heritage TLand Banner Maxx reduced the symptoms in earlycurative applications (Figure 3). Although BannerMaxx and other DMI fungicides can induceddetrimental growth regulation of bermuda in sum-mer, detrimental effects noted in these trials werenegligible.

It should be noted however that we can'trely on multiple applications of DMI fungicidesfor control due to unwanted growth regulationproblems that will result. Best results wereobtained with rotations and post application irri-gation experiment (Figure 4), where we looked attank-mixes or rotations of some fungicides that

previously had shown some efficacy. The besttreatment was a simple rotation of Heritage TL (1fl oz) followed by Medallion (0.5 oz) after 2weeks, and then a final application of Headway (apremix of azoyxystrobin and propiconazole) at1.5 fl oz. Efficacy was boosted in both programsby applying irrigation immediately after sprayswere applied with 0.5 inches of water.

In 2009 to date, the disease has been muchless severe overall, although a few notable epi-demics have occurred. Courses with a history ofthis disease have adopted a strategy of increased,judicious fertilization throughout summer, as wellas preventive fungicide applications. In trialsshown here and in other trials, fungicides withexcellent activity against Rhizoctonia-induceddiseases have been beneficial, but applicationsmust be applied preventively.

It is suggested that superintendents beaware of the potential for this disease to developand scout greens routinely beginning in earlysummer. If off-color (bronze) rings begin to devel-op, take a sample and submit to a lab with a quickturn-around time before treating. Rhizoctonia candevelop quickly in a sample that has not beentreated with fungicides, so an answer should beforthcoming and can give some information thatmay be valuable in determining if fungicide treat-ments are warranted.

Acknowledgements

I wish to thank the USGA’s Turfgrass andEnvironmental Research Program and Syngentafor providing funds to support the research con-ducted to date with this disease.

Literature Cited

1. Aoyagi T., K. Kageyama, and M. Hyakumachi.1998. Characterization and survival ofRhizoctonia solani AC 2-2 LP associated withlarge patch disease of zoysiagrass. Plant Disease82:857-863. (TGIF Record 53270)

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2. Burpee, L. 1980. Rhizoctonia cerealis causesyellow patch of turfgrasses. Plant Disease64:1114-1116. (TGIF Record 1401)

3. Burpee, L., and S. B. Martin. 1996. Biology ofturfgrass diseases incited by Rhizoctonia species.Pages 359-368. In B. Sneh, S. Jabaji-Hare, S.Neate, and G. Dijst (eds.) Rhizoctonia Species:Taxonomy, Molecular Biology, Ecology,Pathology, and Disease Control. KluwerAcademic Publ., Dordrecht, The Netherlands.(TGIF Record 155038)

4. Carling, D. E. 1996. Grouping in Rhizoctoniasolani by hyphal anastomosis reaction. Pages 37-47. In B. Sneh, S. Jabaji-Hare, S. Neate, and G.Dijst (eds.) Rhizoctonia Species: Taxonomy,Molecular Biology, Ecology, Pathology, andDisease Control. Kluwer Academic Publ.,Dordrecht, The Netherlands.

5. Christensen, M. J. 1979. Rhizoctonia speciesassociated with diseased turfgrasses in NewZealand. N.Z. Journal of Agricultural Research22:627-629. (TGIF Record 2240)

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7. Elliott, M. L. 1999. Comparison of Rhizoctoniazeae isolates from Florida and Ohio turfgrasses.HortScience 34:298-300. (TGIF Record 21289)

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11. Martin, S. B., L. T. Lucas, and C. L. Campbell.1984. Comparative sensitivity of Rhizoctoniasolani and Rhizoctonia-like fungi to selectedfungicides in vitro. Phytopathology 74:778-781.(TGIF Record 355)

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13. Mushika, T., K. Kageyama, and M.Hyakumachi. 1994. Genetic identification of largepatch fungus of warm-season turfgrass,Rhizoctonia solani AG 2-2 (LP), based on PCR-RFLP analysis. Ann. Phytopath. Soc. Japan60:772. (TGIF Record 155128)

14. Oniki, M. , A. Ogoshi, T. Araki, R. Sakai, andS. Tanaka. 1985. The perfect state of Rhizoctoniaoryzae and R. zeae and the anastomosis groups ofWaitea circinata. Trans. Mycol. Soc. Japan26:189-198. (TGIF Record 155120)

15. Ryker, T. C., and F. S. Gooch. 1938.Rhizoctonia sheath spot of rice. Phytopathology28:233-246.

16. Stiles, C. M., P. F. Harmon, and K. E.Kenworthy. 2008. Relative pathogenicity andfungicide sensitivity of isolates of Rhizoctoniaand other fungal pathogens and the diseaseresponses of seashore paspalum and zoysiagrasscultivars. Page 6. In J. L. Nus (ed.) 2008 USGATurfgrass and Environmental Research Summary.USGA, Far Hills, NJ. (TGIF Record 144225)

17. Toda, T., T. Mushika, T. Hayakawa, A. Tanaka,T. Tani, and U. Hyakumachi. 2005. Brown ring

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patch: a new disease on bentgrass caused byWaitea circinata var. circinata. Plant Disease89:536-542. (TGIF Record 111601

18. Voorhees, R. K. 1934. Sclerotial rot of corncaused by Rhizoctonia zeae, n.sp. Phytopathology24:1290-1303.

19. Warcup, J. H., and P. H. B. Talbot. 1962.Ecology and identity of mycelium isolated fromsoil. Transactions of the British MycologicalSociety 45:495-518.

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