Golf Course Management

MAR 2014

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84 GOLF COURSE MANAGEMENT 03.14 teria (using the previously described meth- ods) was positive for X. translucens. Etiolation symptoms persisted over multiple weeks, but a decline in turf quality was not observed. Etiolation has been previously suggested as a precursor to bacterial wilt, caused by X. translucens pv. poae, on annual bluegrass (Poa (Report) First report of stubby root caused by Trichodorus obtusus on zoysia and bermuda in South Carolina In September 2011, diagnostic samples were taken from Tifway bermudagrass (Cyn - odon dactylon × C. transvaalensis) tees and from Emerald zoysiagrass (Zoysia japonica) roughs of a golf course in Charleston, S.C. Additional samples were taken from a sod farm located near Charleston from a feld of Empire zoysiagrass. The soil was sandy loam, and the samples were taken at a depth of 4-6 inches (10-15 cen - timeters) from symptomatic turf. Symptoms on bermudagrass and zoysiagrass included stubby roots and lightly to severely chlorotic or dead patches of irregular sizes and shapes. Nematodes were extracted by sugar centrifu - gal-fotation and counted. The predominant nematode species recovered was a stubby root nematode, Tric odorus obtusus Cobb. Nema - tode densities were 30 to 170/6.1 cubic inches (100 cubic centimeters) of soil (average 94, n = 5) at the sod farm, and 30 to 230 (average 107, n = 7) at the golf course. Tri odorus obtusus has been reported as a pathogen of bermudagrass in Florida, where it is more damaging than Paratric odorus minor, the other stubby root nematode com - monly associated with turfgrass. In Florida, a density of 120 T. obtusus/6.1 cubic inches is considered high risk. We have encountered several additional samples from across South Carolina with similar or higher densities since our frst diagnosis. Infested soil (94 individuals/6.1 cubic inches) collected from the sod farm was put into columns and planted with Empire sod and maintained in the greenhouse. After 140 days, the population density increased to an average of 230 individuals/6.1 cubic inches of soil. Plants were prone to wilting, and new root growth showed symptoms similar to those observed in the feld. Morphologic and morphometric identi - fcation of T. obtusus was made by examin- ing male and female specimens in temporary water mounts. Males had ventrally curved spicules with three ventral precloacal papil - lae, with the posterior papilla just anterior to the head of the retracted spicules, one ven - tromedian cervical papilla anterior to the excretory pore, and tail with non-thickened terminal cuticle. Females had a deep, bar - rel-shaped, pore-like vulva, and one or two postadvulvar lateral body pores on each side. Males and females had distinctly offset esophagus. Females (n = 10) were 1,100 to 1,440 (1,250) micrometers long, body width 40 to 53 (45) micrometers, onchiostyle 63 to 75 (67) micrometers, and V 583 to 770 (673) micrometers. Males (n = 10) were 1,076 to 1,353 (1,222) micrometers long, body width 33 to 45 (39) micrometers, onchiostyle 62 to 69 (65) micrometers, and spicule 55 to 63 (59) micrometers. A section of the rDNA region was se - quenced from individuals representing the two locations. A search revealed no similar sequences to those of our two populations. As such, it appears that these are the frst se - quences of this portion of the rDNA for T. obtusus, although a different, non-overlap - ping portion was found under the synonym T. proximus. To our knowledge, this is the frst report of T. obtusus on zoysiagrass and the frst report of the species on bermuda - grass in South Carolina. Source: Plant Disease, June 2013, 97(6):852. http://dx.doi.org/10.1094/PDIS-10-12-0932-PDN J B. Shaver is a graduate student in plant and environ - mental sciences; P. Agudelo, Ph.D. (pagudel@clemson. edu), is an associate professor and nematologist; and S.B. Martin, Ph.D., is a professor in turfgrass pathology in the School of Agricultural, Forest and Environmental Sciences, Clemson University, Clemson, S.C. annua L.), and Acidovorax avenae has also been shown to produce etiolation on creep - ing bentgrass. To our knowledge, this is the frst confrmation of X. translucens as a cause of etiolation in creeping bentgrass. Source: Plant Disease, 2014, in press. http://dx.doi.org/10.1094/PDIS-05-13-0565-PDN Joseph Roberts, M.S., is a graduate research assistant; Lane Tredway, Ph.D., is an associate professor; and David F. Ritchie, Ph.D. (david_ritchie@ncsu.edu), is a professor and Extension specialist in the department of plant pathol - ogy, North Carolina State University, Raleigh, N.C. (Above) Trichodorus obtusus female from South Carolina (length = 1,235 micrometers). (Right) Root symptoms of the stubby root nematode, T. obtusus, on zoysiagrass. Photos by Brad Shaver 078-095_March14_TechwellCuttingEdge.indd 84 2/18/14 1:46 PM

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