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Jonathan M. Bokmeyer, Stacy A. Bonos, and William A. Meyer

( Beard, 1973 ). The most devastating disease of tall fescue is brown patch caused by Rhizoctonia solani Kühn. Brown patch can reduce the overall quality and aesthetics of the turf stand ( Couch, 1985 ; Martin and Lucas, 1984 ) and reduce stand density

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Matthew A. Cutulle, Jeffrey F. Derr, David McCall, Brandon Horvath, and Adam D. Nichols

. However, the major limiting factor to tall fescue’s success as a turf in the transition zone is its susceptibility to the fungal pathogen R. solani Kuhn ( Piper and Coe, 1919 ), which causes the disease brown patch in the summer months. Brown patch is

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Michael A. Fidanza and Peter H. Dernoeden

A field investigation was conducted during 1991 and 1992 to determine the effectiveness of enzyme-linked immunosorbent assay (ELISA) to predict brown patch (Rhizoctonia solani Kühn) infection events in `Caravelle' perennial ryegrass (Lolium perenne L.). Turfgrass samples were collected either between 7:00 and 8:00 am or 4:00 and 5:00 pm, and from plots mowed to a height of either 1.7 or 4.5 cm. Pathogen detection levels were generally higher in am-sampled turf and in plots mowed to a height of 4.5 cm. During 2 years, only 7 of 15 infection events were predicted from samples collected from high-cut turf and only three from samples collected from low-cut turf. While this technology is useful for confirming the presence of R. solani, it was unreliable for predicting infection events.

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Glenn A. Hardebeck, Ronald F. Turco, Richard Latin, and Zachary J. Reicher

Pseudomonas aureofaciens strain Tx-1 is suggested as a biological control for Sclerotinia homoeocarpa (F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn) on golf courses. To overcome application difficulties, a field bioreactor is used to grow Tx-1 daily and then inject into nightly irrigation on the golf course. Though Tx-1 shows some promise for disease control in vitro, it is relatively untested under field conditions. We conducted three field experiments to 1) evaluate the efficacy Tx-1 when applied through an irrigation system for the control of dollar spot and brown patch; 2) determine if there is an interaction between nitrogen fertility or fungicides on efficacy of Tx-1; and 3) determine if Tx-1 can extend the duration of dollar spot control by a single application of fungicide. Nightly applications of Tx-1 through irrigation did not affect brown patch on `Astoria' colonial bentgrass (Agrostis capillaris Sibth.) during the 2 years of our study. Tx-1 reduced dollar spot in `Crenshaw' creeping bentgrass (Agrostis palustris Huds.) by 37% in 1998 compared to non-Tx-1 treatments, but Tx-1 had no effect on dollar spot in 1999. Under low disease pressure, Tx-1 increased the dollar spot control of fungicides by 32% and increased the duration of control by 2.6 days. However, Tx-1 had no effect on fungicide efficacy or duration of control later in the summer when dollar spot pressure was high. Fungicides did not negatively affect Tx-1's control of brown patch or dollar spot, nor did fertilizer regime affect brown patch or dollar spot control by Tx-1. Although delivery of Tx-1 in our studies was optimized, disease control was marginal and occurred only under low disease pressure. Therefore, we conclude Tx-1 has limited practical value for turfgrass disease control on golf courses.

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Joon Lee, Jack Fry, and Ned Tisserat

There is interest in identifying cultural practices that may reduce fungicide requirements of creeping bentgrass (Agrostis palustris Huds.) putting greens. Our objective was to evaluate the plant defense activator ASM in combination with 12 biostimulants for the potential to reduce dollar spot (Sclerotinia homoeocarpa F.T. Bennett) and brown patch (Rhizoctonia solani Kuhn) in a blend of `Cato: `Crenshaw creeping bentgrass during 2000 and 2001. The experimental design was a split-plot with ASM as the whole plot, and biostimulants as the subplots. ASM was applied biweekly as a.i. at 35 g·ha-1 and biostimulants were applied according to manufacturers recommendations. Sclerotinia homoeocarpa infection centers were reduced by 38% with ASM, but levels were >1500/m2 in Aug. 2000, and turf quality was unacceptable through most of the study period. No suppression of brown patch occurred with ASM. None of the biostimulants reduced dollar spot or brown patch in creeping bentgrass when compared to biweekly applications of soluble N at 4.9 kg·ha-1. Dollar spot suppression achieved with ASM warrants additional studies to determine how it might be used to reduce fungicide inputs on creeping bentgrass putting greens. Chemical name used: acibenzolar-S-methyl (ASM).

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Ken Obasa, Jack Fry, and Megan Kennelly

light brown to straw-colored sunken patches with or without bright orange margins ( Green et al., 1993 ; Smiley et al., 2005 ; Tisserat et al., 1994 ). Patches can range in size up to 6 m or more in diameter ( Green et al., 1993 ; Tisserat et al

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Travis C. Teuton, John C. Sorochan, Christopher L. Main, Thomas J. Samples, John M. Parham, and Thomas C. Mueller

( Puccinia graminis Persoon subsp. graminicola Urban) and dollar spot ( Sclerotinia homoeocarpa Bennett) in Kentucky bluegrass and brown patch [ Rhizoctonia solani (Kühn)] in tall fescue can occur under these stressful conditions ( Landshchoot and Park

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J.H. Dunn, D.D. Minner, B.F. Fresenburg, and S.S. Bughrara

We evaluated the effect of fertilization treatments in combination with clippings disposal on perennial ryegrass (Lolium perenne L.) in two adjacent locations. Clippings left on turf during mowing decreased dollar spot (Sclerotinia homoeocarpa F.T. Bennett) in both locations during three summers compared with clippings removed in mower baskets. However, brown patch (Rhizoctonia solani Kuhn) increased during July and Aug. 1995 when clippings were left on turf. Dollar spot was more severe with N (kg·ha–1·year–1) at 120 compared to 240; brown patch was more severe at 240. While clippings disposal had significant effects on disease incidence, implementation may not be practical because of the contrary responses of the observed diseases to this management approach.

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Christopher J. Clark and Douglas M. Burmeister

Development of browning induced in `Braeburn' apple (Malus ×domestica Borkh.) fruit by a damaging CO2 concentration was monitored weekly using magnetic resonance imaging (MRI) during a 4-week storage trial (0.5 °C, 2 kPa O2/7 kPa CO2). Discrete patches of high-intensity signal, distributed randomly throughout the fruit, were observed in multislice images of samples after 2 weeks of storage; these patches were eventually confirmed as being sites of browning reactions after dissection at the end of the trial. Subsequently (weeks 3 and 4), signal intensity at sites of incipient damage increased and patches enlarged and coalesced. After 2 weeks of storage, the extent of affected tissue, averaged across all image slices, was 1.5%, increasing to 15.9% and 21.3% after 3 and 4 weeks. The average rate at which tissue damage spread in individual slices was 0.81 (range: 0–3.70) cm2·d–1 between weeks 2 and 3, declining to 0.32 (range: 0–1.55) cm2·d–1 in the final week. Tissue damage induced under these conditions did not spread at the same rate at all locations within individual fruit, nor was it preferentially located toward the stem or calyx ends of the fruit.

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P.H. Dernoeden and M.S. McIntosh

Little is known about deleterious or beneficial nontarget effects of fungicides applied to turfgrasses. Five fungicides from several chemical classes were applied six times annually over 5 years to field plots of either `Regal' or `Fiesta' perennial ryegrass (Lolium perenne L.). All fungicides improved turfgrass quality during Spring 1984, Summer 1984 and 1985, Fall 1984, and Winter (except benomyl and chlorothalonil) 1985. Improved quality in Spring 1984 was attributed to red thread [Laetisaria fuciformis (McAlp.) Burds.] control; whereas, improved quality in Summer 1985 was due to brown patch (Rhizoctonia solani Kuhn.) control. For other years and seasons, the mechanism of improved quality provided by the fungicides was not determined. Other than red thread and brown patch control, few nontarget benefits and no nontarget detriments were observed visually with multiple applications of the fungicides evaluated. Chemical names used: methyl[1-butylamino carbonyl]-1H-benzimidazol-2-yl]carbamate(benomyl); tetrachloroisophthalonitrile (chlorothalonil); 1-isopropyl-carbamoyl-3-(3,5-dichlorophenyl) hydantoin (iprodione); bis(dimethyl-thio-carbamoyl) disulfide (thiram); and 1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-y1)-2-butanone (triadimefon).