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  • Author or Editor: Peter H. Dernoeden x
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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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Abstract

The purpose of this study was: (a) to determine effective dosages of preemergence herbicides for season-long crabgrass [Digitaria ischaemum (Schreb.) Muhl.] control in the transition zone; and (b) to determine if reduced rates of herbicides applied in subsequent years would provide satisfactory crabgrass control. A single application of bensulide (8.5 kg ha-1) provided effective (>90%) crabgrass control in all 3 years of the study. Oxadiazon (4.5 kg ha-1) effectively controlled crabgrass, and reducing the rate of oxadiazon to 2.2 kg ha-1 in the 2nd year, or reducing the rate to either 1.1 or 1.1 + 1.1 kg ha-1 in the 3rd year also gave excellent crabgrass control. Single and sequential applications of benefin did not provide satisfactory control in the initial year of use. Benefin applied at 2.2 + 2.2 kg ha-l provided acceptable control in the 2nd year, whereas it was not until the 3rd year that a single application (2.2 kg ha-1) was efficacious. The lowest effective dosage of DCPA was 8.4 + 8.4 kg ha-1; however, consistently good results were provided by 11.8 + 5.9 kg ha-1 of DCPA. Single and sequential applications of siduron did not effectively control crabgrass in any year.

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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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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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Abstract

Fenoxaprop is an effective postemergence herbicide for summer annual grass weed control in cool-season turfgrasses. Following emergence of smooth crabgrass [Digitarla ischaemum (Schreb.) Muhl.] and goosegrass [Eleusine indica (L.) Gaertn.], fenoxaprop was applied alone or in combination with one of several preemergence herbicides. The objective of these field studies was to determine whether these herbicide combinations would provide both effective postemergence control of smooth crabgrass and goosegrass, as well as subsequent preemergence control of annual grass weed seed germinating thereafter. When fenoxaprop was applied alone in June or July to smooth crabgrass, the level of control ranged from poor (40%) to excellent (99%), depending on herbicide rate and timing of application. Smooth crabgrass control was erratic where plants had more than four tillers, particularly on a droughty site. When fenoxaprop (0.17, 0.20, or 0.39 kg·ha–1) was applied in combination with bensulide, benefin, DCPA, oxadiazon, pendimethalin, or prodiamine, excellent (90% to 100%) season-long smooth crabgrass control was achieved. Fenoxaprop + preemergence herbicide combinations exhibited complementary action, particularly in tank mixes applied to tillered smooth crabgrass. Fenoxaprop applied alone controlled goosegrass (two-leaf to three-tiller stage), but goosegrass reinfested treated plots from seed germinating after the herbicide application. When fenoxaprop (0.20 kg·ha–1) was applied with oxadiazon (2.2 kg·ha–1) to nontillered goosegrass, exceptional (99%) season-long goose-grass control was achieved. Chemical names used: (±)-ethyl 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy] propanoate (fenoxaprop); N-butyl-N-ethyl-2,6-dinitro-4-trifluoromethyl)benzenamine (benefin); O,O-bis(l-methylethyl)-S-[2-[(phenylsulfonyl)amino]ethyl]phosphorodithioate (bensulide); dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate (DCPA); 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-l,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin); 2,6-dinitro-N 1,N 1,-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine (prodiamine).

Open Access

Abstract

Stripe smut [Ustilago striiformis (West.) Niessl.] is a destructive disease of ‘Merion’ and several other cultivars of Kentucky bluegrass [Poa pratensis L.). Fungicides (all in kg·ha-1) were foliar-applied to a diseased stand of ‘Merion’ Kentucky bluegrass in spring while disease symptoms were evident. In the initial study, sequentially applied (14-day interval) triadimefon (3.0 + 3.0) and terbuconazole (1.6 + 1.6) provided excellent control and commercially acceptable turfgrass quality 2 years after fungicide application. Propiconazole (1.7 + 1.7) provided good disease control; however, benomyl (6.1 + 6.1), fenarimol (3.0 + 3.0), iprodione (6.1 + 6.1), and prochloraz (7.6 + 7.6) provided poor disease control when plots were rated 2 years following application. In the second study, a single application of terbuconazole (1.6) and diniconazole (1.5 or 3.0) provided excellent stripe smut control, and turf exhibited commercially acceptable quality 2 years following fungicide application. Triadimefon-(1.5 or 3.0), terbuconazole- (0.8), and propiconazole- (1.7) treated turf exhibited reduced disease injury after 2 years; however, turf quality was not as good as that provided by the other fungicide treatments. Observations and data collected over 3 years do not support the view that U. striiformis-infected plants die during summer stress periods, thereby controlling the disease by reducing large populations of perennially infected plants. Chemical names used: methyl[1-[(butylamino)carbonyl]-1H-benzimidazol-2-yl]carbamate (benomyl); α-(2-chlorophenyl)-α-(-4-chlorophenyl)-5-pyrimidinemethanol (fenarimol); 1-isopropylcarbamoyl-3-(3,5-dichlorophenyl) hydantoin (iprodione); 1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(l,2,4,-triazol-1-yl)-1-peneten-3-ol (diniconazole is proposed); N-propyl-N-[2-(2,4-6-trichlorophenoxy)ehyl]-1H-imidazole-1-carboxamide (prochloraz); 1-(2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl methyl)-1H,2,4-triazole (propiconazole); a-[2-(4-chlorophenyl)ethyl]-a-(1,1-dimethylethyl)-H-l,2,4-triazole-1-ethanol (terbuconazole is proposed); 1-(4-chlorophenoxy)-3,3-dimethyl-1-(lH-l,2,4-triazol-1-yl)-2-butanone (triadimefon).

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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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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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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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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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