Factors Associated with Populations of Plant-Parasitic Nematodes in Bentgrass Putting Greens in Oklahoma

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1 Ftors Assoited with Popultions of Plnt-Prsiti Nemtodes in Bentgrss Putting Greens in Oklhom N. R. Wlker, Deprtment of Entomology nd Plnt Pthology; C. L. God, Deprtment of Sttistis; H. Zhng, Deprtment of Plnt nd Soil Sienes; nd D. L. Mrtin, Deprtment of Hortiulture nd Lndspe Arhiteture, Oklhom Stte University, Stillwter ABSTRACT Wlker, N. R., God, C. L., Zhng, H., nd Mrtin, D. L Ftors ssoited with popultions of plnt-prsiti nemtodes in entgrss putting greens in Oklhom. Plnt Dis. 86: Numerous gener of plnt-prsiti nemtodes re frequently present t high popultions in golf ourse putting greens. The ojetives of this reserh were to identify nd quntify plnt-prsiti nemtodes from Oklhom entgrss putting greens nd to hrterize speifi soil physil nd hemil fetures nd mngement ftors tht my ount for differenes in or ssoited with the oserved nemtode popultions. In the fll of 2000, nemtodes were identified from 99 individul entgrss putting greens smpled from 46 different lotions in Oklhom. In ddition to green ge nd entgrss ultivr; soil ph, nitrte-nitrogen (NO 3 -N), plnt-ville phosphorus nd potssium, orgni mtter (OM), ulk density, nd prtile size distriution were determined for eh green. Expenditures on mngement tivities, inluding fertilizer, heriide, fungiide, nd insetiide, were determined for 20 of the smpled ourses nd ompred with nemtode popultions. Nemtodes from seven gener were found in Oklhom greens, with Crionemell spp. eing the most ommon. Prtrihodorus spp., Tylenhorhynhus spp., nd Heliotylenhus spp. lso were ommon. The logrithmi popultions of ll nemtodes omined inresed with greter green ge (r = 0.37). A negtive reltionship ws oserved etween soil ulk density nd ll nemtodes omined (r = 0.29). Soil NO 3 -N, plntville K, nd OM inresed with omined logrithmi popultions of ll plnt prsiti nemtodes (r = 0.23, 0.28, nd 0.37, respetively). A four-ftor model ounted for 75% of the totl vrition in the dt nd permitted groupings of ll vriles into four unorrelted ftors. Totl logrithmi nemtode popultions inresed with fungiide nd heriide expenditures (r = 0.31). This study suggests tht popultions of plnt-prsiti nemtodes my e influened y the putting green ioti soil environment nd possily indiretly y mngement prties on putting greens. Additionl keywords: Agrostis plustris, ulk density, Crionemell, Heliotylenhus, Hoplolimus, Prtrihodorus, Tylenhorhynhus Creeping entgrss (Agrostis plustris Huds.) is n importnt omponent of putting greens in the southern United Sttes. To hieve high-qulity putting surfe, entgrss is mintined t very low heights (<4 mm) nd is grown in root zone predomintely omposed of snd or sndpet mixture (19). Although tolernt of low mowing heights, entgrss green qulity n e redued y hot tempertures, resulting in redution in root growth nd susequent reovery from wer or disese. To Corresponding uthor: N. R. Wlker E-mil: wlkenr@okstte.edu Pulished with the pprovl of the Diretor, Oklhom Agriulturl Experiment Sttion, Stillwter. This projet ws supported in prt y the Oklhom Integrted Pest Mngement Progrm nd the Oklhom Agriulturl Experiment Sttion projet Aepted for pulition 1 Mrh Pulition no. D R 2002 The Amerin Phytopthologil Soiety mintin high-qulity putting surfe, greens re intensely mnged with pestiides, fertilizer, nd irrigtion to prevent disese, dmge from wer, nd defiienies in fertility nd moisture, nd to minimize deleterious effets due to extremes in environmentl onditions. In spite of efforts to mintin turf density, vigor, qulity, nd disese suppression, greens often fil to respond to mngement inputs nd to mintin desirle putting surfe. This often ours during wrm periods, when use is frequent nd environmentl onditions re onduive for disese. These onditions often re present when plntprsiti nemtodes re present t their highest popultions (17). Plnt-prsiti nemtodes re importnt yield-reduing pests of most gronomi rops worldwide. Nemtodes typilly feed on suterrnen plnt tissues, inluding roots, tuers, nd rhizomes. Feeding rrely uses plnt deth; however, nemtodes n rrest root growth nd use lesions, nerosis, or impired root funtion. For gronomi rops, ffeted plnts re hloroti, stunted in growth, hve lower yields, nd often re more suseptile to diseses used y fulttive miroes. Turf grss growth n e stunted y nemtodes nd stnds of turf n eome less dense. For speifi nemtode turf omintions, the ffeted turf grss my die. In ddition, lrge numers of plnt-prsiti nemtodes in entgrss putting green my interfere with the effetiveness of mngement inputs, suh s nutrient uptke y plnts. Plnt-prsiti nemtodes from numerous gener often re present in putting greens. Heliotylenhus, Crionemell, Hoplolimus, nd Tylenhorhynhus spp. were found in 55, 52, 47, nd 38%, respetively, of 81 greens from 20 Knss golf ourses (18). Men nemtode popultions in the study were 425, 900, 81, nd 242/100 m 3 soil for Heliotylenhus, Crionemell, Hoplolimus, nd Tylenhorhynhus spp., respetively. Similr results were found in n erlier study onduted in New York in whih Crionemell, Tylenhorhynhus, Hoplolimus, nd Heliotylenhus spp. were present in 78, 71, 55, nd 39%, respetively, of 295 smples olleted from 16 golf ourses; however, men popultion vlues were not reported (11). Flututions or distriution differenes of nemtode popultions re ommon in turfgrss eosystems. Flututing popultions of Belonolimus longiudtus prsitizing Bermudgrss in Cliforni were orrelted with soil tempertures (r 2 = 0.40) (2). In Illinois, Tylenhorhynhus nudus, Heliotylenhus ornurus, nd Crionemell urvt were more frequently reovered from the upper 2.5 m of entgrss putting green thn from 2.5- to 5.0- m depths (4). However, in New Englnd, nemtode popultions were not found to e onsistent within green over time (23). The effet of individul nd omined popultions of plnt-prsiti nemtodes on entgrss root nd shoot growth hs een hrterized. In greenhouse studies, only mixed popultions of Hoplolimus spp. nd T. duius redued shoot growth nd used entgrss lef hlorosis (9). A similr redution in shoot growth ws oserved for mixed popultions of Prtylenhus penetrns nd T. gri, ut not for individul nemtode speies (15). The effets of plnt-prsiti nemtodes on entgrss plnts in situ hs een more dif- 764 Plnt Disese / Vol. 86 No. 7

2 fiult to hrterize due to vrile ftors suh s temperture, dmge from other diseses, nd green onstrution. Effetive mngement of plnt-prsiti nemtodes in existing entgrss greens is limited to pplitions of orgnophosphorous pestiides. Conerns out orgnophosphorous pestiide sfety nd fte in the environment ould potentilly limit their use on golf ourses. Older greens tht do not provide eptle turfgrss qulity re either fumigted or reuilt using new root zone medi. These disruptive mngement options usully re reserved until the umultion of orgni mtter or presene of plnt pthogens re thought to e too high to e mnged y stndrd mngement prties suh s the removl of numerous, smll soil ores (erifition) prior to the pplition of snd to the surfe of the green. The snd-sed root zone, ontinul presene of plnts, nd sene of flututing soil wter ontent likely enourge n inrese in popultions of plnt-prsiti nemtodes. However, ommunities of plnt-prsiti nemtodes in entgrss greens from the sme region n differ drmtilly (21). Previous studies of nemtode distriution in entgrss greens hve not exmined ftors whih ould ount for differenes in nemtode popultions. The ojetives of this reserh were to identify nd quntify plnt-prsiti nemtodes from Oklhom entgrss putting greens nd to hrterize speifi soil physil nd hemil fetures nd mintenne expenditures tht my ount for differenes in or re ssoited with the oserved nemtode popultions in the greens smpled. MATERIALS AND METHODS From Septemer through the first week of Novemer 2000, soil smples were olleted from 99 entgrss putting greens from 43 golf ourses nd 3 reserh filities in Oklhom. Smples, one from eh green, were olleted with up utter (10.8 m in dimeter) to depth of out 10 m. Green ge nd entgrss ultivr were reorded t the time of smpling for eh green. Soil smples were stored (<2 weeks) t 4 C nd thth ws removed prior to nlysis. Nemtodes were extrted from 100-m 3 susmple of soil y sieving nd entrifugl flottion (1). Plnt-prsiti nemtodes were identified to genus, nd totl popultions from 100 m 3 of soil were determined using ompound light mirosope. A portion of eh soil smple (>200 m 3 ) ssyed for nemtodes ws ir dried on greenhouse enh for minimum of 1 week, ground with rotry impt grinder, nd sieved (<2 mm). All smples were nlyzed for ph, nitrte-nitrogen (NO 3 -N), plnt-ville phosphorus (P) nd potssium (K), nd soil orgni mtter (OM). Soil ph ws mesured y glss eletrode in 1:1 soil:wter suspension (16). Soil NO 3 - N ws extrted with 1 M KCl solution nd quntified y the dmium redution method (7). Plnt-ville P nd K were extrted using the Mehlih 3 solution (10). Soil OM ws determined from orgni ron (C) using dry omustion C nlyzer (12) nd onversion ftor of (sed on orgni mtter ontining 58% C). To determine soil ulk density nd the distriution of snd prtile sizes, seprte soil susmple (31 m 3 ) ws dried for 24 h t 70 C in fored-ir oven nd then weighed. Smples then were heted to 510 C in furne for 24 h to remove orgni mtter. Dry snd frtions were seprted into United Sttes Deprtment of Agriulture defined limits for si soil texturl lsses y virting for t lest 1 min on nested sieves of 2,000, 1,000, 500, 250, 106, nd 53 µm over pn (3). Snd frtions olleted on eh sieve nd silt with ly frtion olleted inside the pn were weighed. For ll smples, nemtode popultions were trnsformed to log 10 (X + 1) sle for nlysis nd the reltionship etween popultion densities for individul nd totl nemtodes nd soil ftors were ssessed y orreltion nlysis using SAS (SAS Institute, Cry, NC). The reltionship etween golf ourse expenditures (5) on fertilizer, heriide, fungiide, insetiide, djuvnt, snd pplitions, nd nemtode popultions ws ssessed y orreltion nlysis for susmple of 20 different golf ourses from whih 43 greens were Tle 1. Plnt-prsiti nemtode gener present in entgrss putting greens in Oklhom Gener Greens (%) Men/100 m 3 soil SEM d Crionemell Tylenhorhynhus Prtrihodorus Heliotylenhus Prtylenhus Hemiyliophor Hoplolimus Nemtodes were olleted from 99 greens t 46 lotions in the fll of Popultions were determined for 100 m 3 of soil y sieving nd entrifugl flottion. Perent of greens ontining respetive nemtode. Men numer of nemtodes sed on greens hving the respetive nemtode. d Stndrd error of the men. smpled. These 20 ourses vried in mintenne expenditures. Only signifint orreltion oeffiients (P 0.05) re presented. To determine the effet of entgrss ultivr on nemtode popultions, smples ontining only the ultivrs Pennross (Tee-2-Green Corp., Cny, OR) nd SR1020 (Seed Reserh of Oregon In., Corvlis, OR) were seleted for nlysis of vrine. To identify underlying ftors responsile for orreltions mong vriles, ftor nlysis on the soil vriles ws performed using SAS/FACTOR proedure (SAS Institute). Priniple omponent nlysis ws first used for ftor extrtion nd ll ftors with n eigenvlue greter thn one were sujeted to orthogonl rottion using vrimx rottion (SAS Institute). The vriles used were ph, NO 3 -N, plnt-ville P nd K, OM, ulk density, perent snd, nd prtile size distriutions. RESULTS The two most ommon entgrss ultivrs plnted were Pennross nd SR1020, whih were grown on 34 nd 31% of the greens smpled, respetively. Bentgrss mixtures, Pennlinks (Tee-2-Green Corp.), nd Penn A-4 (Tee-2-Green Corp.) were present on 8, 6, nd 6% of the greens, respetively. Five dditionl ultivrs were present on the remining 15% of greens. Plnt-prsiti nemtodes from seven gener were identified in Oklhom entgrss putting greens (Tle 1). Crionemell spp. were found most frequently nd hd the gretest popultion densities in greens where this nemtode ws present. In 28% of the greens with Crionemell spp., its popultions were ove 1,000/100 m 3 of soil. Prtrihodorus ws the seond most frequent nemtode genus found in smples. However, popultion densities of this nemtode genus were generlly the lowest of those nemtodes present in greens. Tylenhorhynhus spp. lso were present in nerly hlf of the greens smpled. Although Heliotylenhus spp. were present in only 32% of greens, popultion densities were usully high. The verge ge of putting greens smpled ws 12.8 yers. Totl omined popultion densities of plnt-prsiti nemtodes inresed with green ge (r = 0.37). Individul popultions of Crionemell, Tylenhorhynhus, nd Heliotylenhus spp. lso inresed with green ge (Tle 2). NO 3 -N, plnt-ville P nd K, nd OM in the soil lso inresed with inresing green ge (r = 0.34, 0.31, 0.26, nd 0.74, respetively). Soil ph rnged from 5.6 to 8.8, with n verge of 7.4. However, ph ws not orrelted with individul or omined nemtode popultion densities. Numers of Crionemell nd Tylenhorhynhus spp. inresed with inresing NO 3 -N ontent of greens. Popultions of Crionemell, Tylenhorhynhus, nd Heliotylenhus Plnt Disese / July

3 spp. inresed with greter plnt-ville P nd K, nd OM ontent. A negtive reltionship ws oserved etween soil ulk density (0.85 to 1.75 g/m 3, 1.21 g/m 3 verge) nd popultions of Prtrihodorus, Heliotylenhus, nd omined popultions of plnt prsiti nemtodes (r = 0.28, 0.27, nd 0.29, respetively). In ddition, only NO 3 -N, plnt-ville K, nd OM inresed with popultion densities of ll plnt-prsiti nemtodes omined (r = 0.23, 0.28, nd 0.37, respetively). Soil smples were omposed primrily of snd (85.2 to 98.9%, 94.7% verge) nd prtile size distriution ws primrily limited to prtiles less thn 1 mm in dimeter nd greter thn 106 µm in dimeter (>2 mm, 0.95%; 1 mm to 2 mm, 6.5%; 500 µm to 1 mm, 24.3%; 250 to 500 µm, 40.1%; 106 to 250 µm, 20.4%; 53 to 106 µm, 2.4%). Popultion densities of Hoplolimus spp. were negtively orrelted with the perentge of snd frtion etween 500 µm nd 1 mm (r = 0.22). Popultions of Hoplolimus nd Crionemell spp. inresed s the perent of snd frtion etween 106 nd 250 µm in dimeter inresed (r = 0.20 nd 0.21, respetively). Totl popultions of plnt-pthogeni nemtodes deresed s snd frtions greter thn 1 mm inresed (r = 0.26 [1 mm] nd 0.21 [2 mm], respetively). Popultions of Crionemell spp., Tylenhorhynhus spp., nd ll omined plnt-prsiti nemtodes were greter in greens plnted with v. Pennross (P 0.001). However, the ge of greens plnted with the entgrss v. Pennross ws, on verge, 12.6 yers older thn greens plnted with SR1020 entgrss (P ). In the ftor nlysis, eigenvlues for the first four ftors were greter thn one nd ounted for 75% of the totl vrition for the soil vriles (Tle 3). The first ftor ounted for 33.8% of the totl vrition in the soil vriles, nd hd high positive ftor loding on the 106- to 250- µm snd frtion grouping, moderte lodings for N nd K, nd negtive lodings for the frtion groupings etween 0.5 nd 2 mm in dimeter (Tle 3). The seond ftor ounted for 17.9% of the totl Tle 2. Vlues nd orreltion oeffiients for soil ftors nd nemtode popultions from entgrss putting greens in Oklhom Ftors (kg/h) Green ge (yers) NO 3 -N Mehlih 3, P Mehlih 3, K Orgni mtter (%) Men d Minimum Mximum Correltion oeffiients e Crionemell Tylenhorhynhus Heliotylenhus 0.33 NS Determined y extrtion with 1 M KCl solution nd quntified y the dmium redution method; NO 3 -N = nitrte-nitrogen. Determined y extrtion using Mehlih 3 solution; P = phosphorus, K = potssium. Determined using dry omustion ron nlyzer. d Nemtodes were olleted from 99 greens t 46 lotions in the fll of Popultions were determined for 100 m 3 of soil y sieving nd entrifugl flottion nd trnsformed prior to nlysis log 10 (X + 1). e r vlues signifint t P 0.05, NS = not signifint. Tle 3. Rotted ftor lodings nd ommunlities of four-ftor model for physil nd hemil soil properties of golf ourse putting greens nd plnt-prsiti nemtode popultions Ftor lodings Soil vrile Communlities ph Nitrogen Phosphorus Potssium Orgni mtter Bulk density Perent snd Frtion >2 mm mm mm µm µm µm Eigenvlues Proportion of totl S vrition for the soil vriles nd hd moderte to high positive lodings for ph, plnt-ville P nd K, ulk density, nd OM. The third ftor ounted for 13.8% of the totl vrition for the soil vriles nd hd high positive lodings for perent snd nd snd frtion etween 250 nd 500 µm in dimeter nd high negtive loding for the frtion etween 53 nd 106 µm. The fourth ftor ounted for 9.5% of the totl vrition in the soil vriles nd hd high positive loding for only the frtion greter thn 2 mm. In regrd to ommunlities (the perent of the vrine of eh vrile ounted for y the ftor nlysis), the four-ftor model explined nerly 80% or etter the vrine for perent snd nd ll snd frtion distriution groups (Tle 3). However, the four-ftor model only explined 53 to 68% of the vrine for the soil ftors, NO 3 -N, plnt-ville P nd K, ph, ulk density, nd OM. Ftor nlysis seprted the set of highly orrelted soil hrteristi vriles into four unorrelted (orthogonl) ftors. Using the ftor sores ssoited with these four ftors, regression nlysis ws performed to model the popultions of plnt-prsiti nemtodes from golf ourse putting greens sed on the informtion in the soil hrteristi vriles. Eh of the four ftors ws termed pg1 (ftor 1), pg2 (ftor 2), pg3 (ftor 3), nd pg4 (ftor 4), where the respetive ftors were desried previously. By using the ftor sores ssoited with these ftors in regression nlysis, multiollinerity prolems inherent in the dt re voided. The resulting regression eqution ws otined: Log popultion = pg pg pg4 (r 2 = 0.25). Fertilizer, insetiide, djuvnt, nd oring or snd pplition expenditures did not orrelte with totl popultion densities of plnt-prsiti nemtodes (dt not shown). Totl plnt-prsiti nemtode popultions inresed with fungiide nd heriide expenditures (r = 0.31 nd 0.43, respetively). Numers of Crionemell spp. inresed with expenditures on djuvnt, fungiide, oring or snd pplition, nd heriide (Tle 4). Popultions of Tylenhorhynhus spp. inresed only with inreses in heriide expenditures, wheres popultions of Prtrihodorus spp. inresed with ll expenditures. In ontrst, numers of Heliotylenhus spp. were not orrelted with ny golf ourse expenditures. DISCUSSION Plnt-prsiti nemtodes were ommon in Oklhom entgrss putting greens. These results re onsistent with those from other studies throughout the United Sttes (4,8,11,13). Crionemoides spp. were the most ommon nemtodes found in these studies, s ws the se in New 766 Plnt Disese / Vol. 86 No. 7

4 York nd Ohio putting greens (11,14). Nemtode popultions hve een reported to vry mong golf ourses nd greens from single ourse (21). Nemtode popultions lso vried onsiderly mong the greens smpled in this study (dt not shown). Greenhouse studies with the entgrss vs. Pennross, SR1020, nd Pennlinks (70% of the ultivrs smpled) indited tht popultion densities of Tylenhorhynhus spp. were not ffeted y turf grss ultivr (22). However, popultion densities of nemtodes were different for the two prominent ultivrs smpled in this study. This proly is due to the greter ge of Pennross-plnted greens, not differenes in entgrss ultivrs. Inresing nemtode popultions, OM, nd plnt-ville P nd K were orrelted with greter green ge. The orreltion of these vriles with ge proly is result of pplitions of fertilizers whih ontin P nd K nd plnt growth whih results in the umultion of orgni mtter in greens over time. In Oklhom, new greens usully re onstruted of snd whih my ontin few free-living ut rrely plnt-prsiti nemtodes. The greter nemtode popultions found in older greens is proly result of nemtodes first eoming estlished nd, susequently, popultions inresing over time. Soil texture hs een doumented to influene plnt-prsiti nemtode popultions. Numerous studies onduted with soils differing in texture hve demonstrted the influene of soil physil hrteristis on nemtode popultion density (20,22). For exmple, Rotylenhulus reniformis popultions were higher thn Meloidogyne inognit for soils hving less snd (6). The mehnism of influene ws suggested to e not result of nemtode exlusion ut rther one whih fvors popultions tht hve ompetitive dvntge over nother speies (6). The uniform snd mixture ontined in putting greens does not permit studies of soil texture ut rther soil prtile size, ulk density, nd hemil differenes s possile ftors in the differenes in nemtode popultions. A limited influene of snd prtile size on nemtode popultions ws found in this study. Although negtive reltionships were present etween nemtode popultion densities nd frtions greter thn 1 mm, this represents less thn 10% of the totl soil prtiles present in greens in this study nd n e onsidered to hve limited effet on nemtode popultions. The results of this study indite tht ulk density ppers to hve n dverse impt on nemtode popultions. Differenes in ulk density ould y ttriuted to the prtile size distriution of snds used in green onstrution nd n inrese over time s result of omption. The mehnism y whih ulk density dversely ffets nemtode popultion density in greens is not known, ut it my e used y greter wter-holding pity of the soil, resulting in derese in nemtode tivity. Ftor nlysis, method to identify underlying ftors tht re responsile for the orreltion mong vriles, n e used to identify reltionships nd mke interprettions not resulting from univrite nlysis. Beuse the ftors re orthogonl to eh other, it is possile to identify the independent effets eh ioti vrile hs on nemtode popultions. The loding of ll soil ftors with the exeption of prtile size on two ftors suggests their importne in ffeting nemtode popultions. However, ommunlities estimted the portion of vrine from eh vrile tht ws explined y the four-ftor model, nd the ommunlities for these vriles were low, whih indites tht muh of the vrile s vrine is not explined. In ontrst, the prtile size grouping for snd loded on ll ftors; however, these lodings were very high nd the ommunlities indite tht most of the vrine ws explined. Golf ourses vry gretly in the intensity of greens mintenne due to udgetry llownes. It hs een suggested tht the high irrigtion, pestiide, nd fertilizer inputs tht entgrss putting greens reeive my redue the detrimentl effets of nemtodes on turf grsses (11,18). The orreltion etween nemtode densities nd expenditures on heriide nd fungiide might support this suggestion, given Tle 4. Correltion oeffiients (r) for golf ourse mintenne expenditures nd plnt-prsiti nemtode popultion densities. Expenditures Gener Adjuvnts Fertilizer Fungiide Heriide Insetiide Snd Correltion oeffiients Crionemoides 0.35 NS NS 0.34 Tylenhorhynhus NS NS NS 0.37 NS NS Prtrihodorus Heliotylenhus NS NS NS NS NS NS Nemtodes were olleted from 43 greens t 20 lotions in the fll of Popultions were determined for 100 m 3 of soil y sieving nd entrifugl flottion nd trnsformed prior to nlysis log 10 (X + 1). Aerifition prior to pplition of snd to the surfe of the green. r vlues signifint t P 0.05, NS = not signifint. the ssumption tht the greter the finnil expenditure the greter the intensity of greens mintenne nd ility of the mnger to ret to the nemtode dmge. The orreltion etween NO 3 -N nd nemtode densities suggests tht the higher NO 3 -N ontent in green soils is the result of greter N use y the greens mnger to offset the effets of low-vigor greens ontining high nemtode popultions. However, it is diffiult to determine if mngement tivities, suh s fertiliztion, re in response to high nemtode popultions or ttriuted to high nemtode popultions, or if mngement tivities possily id plnts in supporting higher nemtode popultions without redution in turf grss qulity. ACKNOWLEDGMENTS We thnk C. E. Mrtin for tehnil ssistne with this study. LITERATURE CITED 1. Ayou, S. M Plnt Nemtology: An griulturl trining id. NemAid Pulitions, Srmento, CA. 2. Bekl, S., nd Beker, J. O Popultion dynmis of the sting nemtode in Cliforni turf grss. Plnt Dis. 84: Blke, G. R., nd Hrtge, K. H Prtile density. In: Methods of Soil Anlysis. Prt 1. Physil nd Minerlogil Methods. SSSA Book Ser: 9. A. Klute, ed. SSSA nd ASA, Mdison, WI. 4. Dvis, R. F., Wilkinson, H. T., nd Noel, G. R Vertil distriution of three nemtode gener in ent grss putting green in entrl Illinois. J. Nemtol. 26: Duxury, D., Mrtin, D., Woods, M., Willoughy, C., Wooten, M., Bloyd, B., nd Mloney, R Oklhom golf ourse mintenne ost survey. Okl. Agri. Stt. Serv., Stillwter, OK. 6. Koenning. S. R., Wlters, S. A., nd Brker, K. R Impt of soil texture on the reprodution of Rotylenhulus reniformis nd Meloidogyne inognit on otton. J. Nemtol. 28: LACHAT QuikChem Method B. LACHAT Instrument, Milwukee, WI. 8. Lus, L. T., Blke, C. T., nd Brker, K. R Nemtodes ssoited with ent grss nd Bermud grss golf greens in North Crolin. Plnt Dis. Rep. 58: Lukens, R. J., nd Miller, P. M Injury to turf grsses y Tylenhorhynhus duius nd Hoplolimus spp. (Astr.) Phytopthology 63: Mehlih, A Mehlih 3 soil test extrtnt: A modifition of Mehlih 2 extrtnt. Commun. Soil Si. Plnt Anl. 15: Mudoh, C. L., Tshiro, H., nd Hrrison, M. B Plnt-prsiti nemtodes ssoited with golf putting-green turf in New York. Plnt Dis. Rep. 62: Nelson, D. W., nd Sommers. L. E Totl ron, orgni ron, nd orgni mtter. In: Methods of Soil Anlysis. Prt 3. Chemil Methods. SSSA Book Ser: 5. D. L. Sprks, ed. SSSA nd ASA, Mdison, WI. 13. Tshiro, H., Mudoh, C. L., nd Apt. W. J Plnt-prsiti nemtodes ssoited with golf putting-green turf in Hwii. J. Nemtol. 61: Sfford., J., nd Riedel, R. M Crionemoides speies ssoited with golf ourse turf in Ohio. Plnt Dis. Rep. 60: Plnt Disese / July

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