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Peter H. Dernoeden

Annual bluegrass (Poa annua L.) is an intractable weed problem on golf courses. Much has been written about annual bluegrass, but there is little documentation of regional germination period(s) and the proper timing of preemergence herbicides targeted for the control of the annual biotype (P. annua ssp. annua [L.] Timm.=AB). The objectives of this field study were to determine the optimum prodiamine rate and timing for effective AB control. The turf was a mature stand of `Kenblue' Kentucky bluegrass (Poa pratensis L.) maintained under conditions similar to those imposed for golf course roughs. Three rates of prodiamine (0.36,0.73, and 1.1 kg·ha-1) were applied on three dates in 1995 (11 Aug., 14 Sept., and 13 Oct.) and 1996 (29 Aug., 16 and 30 Sept.). All rates applied 11 Aug. or 14 Sept. 1995, and 29 Aug. or 16 Sept. 1996 effectively controlled AB. None of the rates applied 13 Oct. 1995 reduced AB cover, and the 0.36 kg·ha-1 rate applied 30 Sept. 1996 provided relatively poor AB control. Data and observations indicated that the major germination period for AB was between late September and early December. Effective AB control was achieved whenever prodiamine, regardless of rate, was applied between mid-August and mid-September. These prodiamine rates and this application window may be effective only in relatively high cut turf (i.e., >5.0 cm) in the mid-Atlantic region. Chemical names used: O,O-bis(1-methylethyl) S-{2-[(phenylsulfonyl)amino]ethyl} phosphorodithioate (bensulide); N 3,N 3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine).

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Peter H. Dernoeden

Festuca species are being seeded into golf course roughs and natural or out-of-bound areas as alternative turfgrasses to replace perennial ryegrass (Lolium perenne L.) in the mid-Atlantic region. The tolerance of fine-leaf fescues to herbicides targeted for annual bluegrass (Poa annua L.) control, such as ethofumesate and prodiamine, is unknown. The objectives of this field study, therefore, were to assess the tolerance of `Rebel II' tall fescue (Festuca arundinacea Schreb.), and the fine-leaf fescue species `Reliant' hard fescue (Festuca longifolia Thuill.), `Jamestown II' Chewings fescue (Festuca rubra L. ssp. commutata Gaud.), and `MX 86' blue sheep fescue (Festuca glauca L.) to various rates, combinations, and times of application of ethofumesate and prodiamine. `Rebel II' was most tolerant of ethofumesate; however, sequential rates ≥0.84 + 0.84 kg·ha-1 reduced quality for 1 or more weeks and 2.24 + 2.24 kg·ha-1 caused unacceptable injury. Single applications of ethofumesate at rates of 0.56, 0.84, and 1.12 kg·ha-1, and sequential treatments of 0.56 + 0.56 and 0.84 + 0.84 kg·ha-1 reduced `Reliant' quality temporarily. Sequential treatments of high rates (i.e., 1.12 + 1.12 and 2.24 + 2.24 kg·ha-1), however, significantly reduced `Reliant' cover. `Jamestown II' was very sensitive to ethofumesate, but recovered from single applications of 0.56, 0.84, and 1.12 kg·ha-1; sequential applications (≥0.84 + 0.84 kg·ha-1) caused unacceptable injury, and rates ≥1.12 + 1.12 kg·ha-1 caused significant loss of cover. The cultivar MX 86 tolerated single applications of 0.56 to 2.24 kg·ha-1 of ethofumesate, but sequential treatments generally reduced quality to unacceptable levels. In one study, `Jamestown II' and `MX 86' were more severely injured when ethofumesate (1.12 or 2.24 kg·ha-1) was applied in October rather than in November. The fescues generally best tolerated a single, November application of ethofumesate at ≤1.12 kg·ha-1. Prodiamine (0.73 kg·ha-1) caused only short-term reductions in quality of `Jamestown II', but was generally noninjurious to the other fescues. Ethofumesate tank-mixed with prodiamine (0.84 + 0.36 or 1.12 + 0.73 kg·ha-1) elicited some short-term reduction in quality, but the level of injury was generally acceptable and injured fescues had recovered by spring. Chemical names used: [±]2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); N 3,N 3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridine-dicarbothioate (dithiopyr).

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Peter H. Dernoeden

Annual bluegrass (Poa annua L.) is an intractable weed problem on golf courses. Much has been written about annual bluegrass, but there is little documentation of regional germination period(s) and the proper timing of preemergence herbicides targeted for the control of the annual biotype (P. annua ssp. annua [L.] Timm. = AB). The objectives of this field study were to determine the optimum prodiamine rate and timing for effective AB control. The turf was a mature stand of `Kenblue' Kentucky bluegrass (Poa pratensis L.) maintained under conditions similar to those imposed for golf course roughs. Three rates of prodiamine (0.36, 0.73, and 1.1 kg·ha-1) were applied on three dates in 1995 (11 Aug., 14 Sept., and 13 Oct.) and 1996 (29 Aug., 16 and 30 Sept.). All rates applied 11 Aug. or 14 Sept. 1995, and 29 Aug. or 16 Sept. 1996 effectively controlled AB. None of the rates applied 13 Oct. 1995 reduced AB cover, and the 0.36 kg·ha-1 rate applied 30 Sept. 1996 provided relatively poor AB control. Data and observations indicated that the major germination period for AB was between late September and early December. Effective AB control was achieved whenever prodiamine, regardless of rate, was applied between mid-August and mid-September. These prodiamine rates and this application window may be effective only in relatively high cut turf (i.e., >5.0 cm) in the mid-Atlantic region. Chemical names used: O,O-bis(1-methylethyl) S-{2-[(phenylsulfonyl)amino]ethyl} phosphorodithioate (bensulide); N 3,N 3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine).

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Jinmin Fu and Peter H. Dernoeden

This field study was conducted to investigate carbon metabolic responses to deep and infrequent (DI) versus light and frequent (LF) irrigation in ‘Providence’ creeping bentgrass (Agrostis stolonifera L.). LF irrigation was performed daily to wet soil to a depth of 4 to 6 cm, whereas DI irrigation was performed at leaf wilt to wet soil to a depth of ≥24 cm. The creeping bentgrass was seeded into a sand-based root zone in 2005 and was maintained as a putting green during the 2006 and 2007 study years. Canopy net photosynthesis (Pn) and whole plant respiration (Rw) were monitored, and water-soluble carbohydrates [WSC (i.e., glucose, fructose, and sucrose)], storage carbohydrates [SC (i.e., fructan and starch)], and total nonstructural carbohydrates [TNC (i.e., the sum of water soluble and storage sugars)] in leaf and root tissue were quantified. Creeping bentgrass subjected to DI irrigation had a lower Pn and a generally similar Rw compared with LF-irrigated bentgrass. DI irrigated bentgrass generally had greater levels of WSC and TNC in leaf tissue in 2006 and similar levels in 2007 when compared with LF-irrigated bentgrass. Leaf SC levels were higher in DI- than LF-irrigated bentgrass in both years. Creeping bentgrass roots subjected to DI irrigation generally had greater SC and TNC levels in both years than were found in LF-irrigated plants. Root WSC levels were higher (2006) or similar (2007) in DI- versus LF-irrigated bentgrass. Irrigating creeping bentgrass at wilt rather than daily to maintain moist soil generally resulted in higher carbohydrate levels in leaves and roots, which may enable creeping bentgrass to better tolerate and recover from drought and other stresses.

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Jinmin Fu and Peter H. Dernoeden

Carbohydrates provide energy required to maintain healthy plant growth in summer. Coring is performed periodically on creeping bentgrass (Agrostis stolonifera L.) putting greens for numerous reasons; however, its impact on carbohydrate metabolism in creeping bentgrass is unknown. The objectives of this 2-year field study were to examine the effects of coring on rates of photosynthesis (Pn) and whole plant respiration (Rw), and to quantify water-soluble carbohydrates [WSC (i.e., glucose, fructose, and sucrose)], storage carbohydrates [SC (i.e., fructan and starch], and total nonstructural carbohydrates [TNC (i.e., WSC + SC)] in creeping bentgrass leaves and roots during the summer. The study site was ‘Providence’ creeping bentgrass grown on a sand-based root zone and was maintained as a putting green. Three coring treatments were assessed as follows: spring-only coring, spring plus three summer corings, and a noncored control. Pn and Rw were measured about 21 d following coring with hollow tines. Pn and Rw rates generally were similar among all three coring treatments in both years. Hence, summer coring had no apparent negative impact on Pn or Rw. Leaf and root WSC, SC, and TNC levels were similar among coring treatments throughout the summer of each year. However, root TNC levels were lower in July of each year in spring plus summer-cored bentgrass versus other coring treatments. By September, leaves and roots from spring plus summer-cored creeping bentgrass had higher TNC levels when compared with spring-only or noncored bentgrass. Leaf and root SC levels from spring plus summer-cored bentgrass were also higher in September than were observed in noncored bentgrass. Spring plus summer coring benefited creeping bentgrass by promoting an accumulation of carbohydrates in late summer, which could assist plants in their recovery from summer stresses.

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Mei Zhang and Peter H. Dernoeden

Determining anastomosis groups (AGs) of Rhizoctonia solani Kühn isolates is tedious and time-consuming. Three previously described methods (i.e., cellophane strip, glass slide, petri dish) were compared to determine which was the most rapid and accurate. Colony characteristics also were assessed to tentatively identify AGs. All techniques were accurate. The cellophane strip method was most time-consuming, and the time required for hyphal overlap with the glass slide method was not generally predictable. Pairing isolates in a petri dish containing a thin layer of water agar was reliable and was the simplest technique. There was little variation in colony pigmentation or sclerotia color, shape, or formation patterns within AG-1 IA (n = 34), AG-2-2 IIIB (n = 46), and AG-4 (n = 5); the former two AGs are the ones most commonly isolated from cool-season turfgrasses. Accordingly, R. solani isolates from turfgrasses may be assigned tentatively to an AG based on colony pigmentation and sclerotial characteristics.

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Michael A. Fidanza and Peter H. Dernoeden

Rhizoctonia blight (RB), incited by Rhizoctonia solani Kühn, is a common disease of cool-season turfgrasses. This 2-year field study was conducted to determine the influence of N source, N application timing, and fungicide treatment on RB severity in `Caravelle' perennial ryegrass (Lolium perenne L.). Ringer Lawn Restore (Ringer), a slow-release N source, was compared to water-soluble urea. Nitrogen was applied according to either a spring (March, May, June, and September) or fall (September, October, November, and May) schedule. Plots received either N only or N plus the fungicide iprodione (3.1 kg a.i./ha applied at 21-day intervals). RB was reduced with fall-applied Ringer compared to spring-applied urea in both years in fungicide-free plots. Nitrogen generally enhanced foliar mycelium growth and RB during the initial infection periods (i.e., late June to late July). By mid- to late August there were extremely high levels of blighting among all fungicide-free treatments. Nitrogen source and N application time had no effect on the level of blighting in iprodione-treated plots. During early disease outbreaks, iprodione did not always prevent foliar mycelium from appearing, but it did protect turf from severe RB. Iprodione reduced blighting, but the level of disease suppression and resulting turfgrass quality provided on the extended spray interval was not acceptable for high-quality golf course fairways. Chemical name used: 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidine carboxamide (iprodione).

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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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John E. Kaminski, Peter H. Dernoeden and Cale A. Bigelow

Natural organic fertilizers require microbial degradation for nitrogen (N) release, but their ability to promote rapid turfgrass establishment has not been well documented in newly constructed sand-based rootzones. This 2-year field study evaluated the influence of two general fertilizer and soil amendment programs for their effect on establishment and quality of three creeping bentgrass (Agrostis stolonifera L.) cultivars—`Crenshaw', `Penn G-2', and `Providence'. Turf was grown on a 4 sand: 1 sphagnum peat (by volume) rootzone mixture. Four treatments consisting of surface-applied synthetic fertilizer (SF; mostly water-soluble N in 1999 and methylene urea thereafter); surface-applied hydrolyzed poultry meal (PM); preplant-incorporated granular humate (GH) with surface-applied SF; and preplant-incorporated PM with surface-applied PM. Turf cover data collected 42 days after seeding (DAS) showed that the rate of establishment was SF+GH incorporated = SF surface-applied >PM surface-applied + PM incorporated >PM surface-applied. Turf cover was ≥96% among all treatments 90 DAS. Rootmass density was greater (18% to 29%) at 103 DAS in GH incorporated plots combined with SF, when compared to all other treatments, but no rootmass differences subsequently were observed. Soil microbial activity generally was highest in PM-treated plots during the first 14 months following seeding, but not thereafter. Turf treated with SF had less microdochium patch (Microdochium nivale (Fr.) Samuels and I.C. Hallett) and more bentgrass dead spot (Ophiosphaerella agrostis Dernoeden, M.P.S. Camara, N.R. O'Neill, van Berkum et M.E. Palm), when compared to PM-treated plots. Slightly less thatch developed in PM-treated turf when compared to plots receiving SF alone by the end of the second year. Penn G-2 and SF generally provided the best overall turf quality. This study demonstrated the beneficial effects of readily available N from SF for rapid establishment and that preplant incorporation of GH initially aided root development.

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Christopher P. Ryan, Peter H. Dernoeden and Arvydas P. Grybauskas

This 3-year field study evaluated the incidence and severity of dollar spot (Sclerotinia homoeocarpa F.T. Bennett) in six creeping bentgrass (Agrostis stolonifera L.) cultivars maintained as a golf course fairway. Comparison of area under the disease progress curve (AUDPC) data clearly indicted two resistance groups among the six cultivars. ‘Crenshaw’ and ‘Backspin’ were classified as highly susceptible (HS) and the other four cultivars (i.e., ‘Penncross’, ‘Providence’, ‘L-93’, and ‘007’) were classified as moderately susceptible (MS) to dollar spot. In all three study years, there were three epidemics that began in May. Data could not be collected in HS cultivars after the first epidemic in each year as a result of severe damage. In MS cultivars, the first epidemic ended and a second began between early July and late August. The second epidemic ended approximately mid-October and a third epidemic appeared in MS cultivars between late October and early December. The second epidemic was longest and most severe, and the third fall epidemic was least severe and of shortest duration. The first epidemic in HS cultivars developed up to two weeks earlier and progressed more rapidly and severely than in MS cultivars. A growing degree-day (GDD) model, using a base air temperature of 15 °C and a start date of 1 Apr., was accurate in predicting the onset of the first epidemic in HS (60 to 70 GDD) and MS (105 to 115 GDD) cultivars during each of the three study years. Growing degree-day models are greatly influenced by the many microclimates found on golf courses and need to be evaluated for accuracy in diverse environments.