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  • Author or Editor: Lambert McCarty x
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Absorption, translocation, and metabolism of foliar-applied 14C-labeled sethoxydim (14C-sethoxydim) in sethoxydim-tolerant centipedegrass [Eremochloa ophiuroides (Munro) Hack.] and sethoxydim-sensitive goosegrass [Eleusine indica (L.) Gaertn.] were determined. The distribution of 14C in treated leaves indicated that similar amounts (≈ 3%) were found in the epicuticular wax fraction (chloroform wash) of both species after 6 hours. After 2 hours, 16% of the applied 14C-sethoxydim was absorbed in the treated leaf by centipedegrass, but only 2% was absorbed by goosegrass. After 2 hours, centipedegrass also readily translocated greater amounts of 14C than goosegrass (4.3% vs. 0.4%). Six hours after treatment, however, no differences were found in amounts absorbed by the treated leaf and translocated to apical and basal leaves. Because sethoxydim-tolerant centipedegrass absorbed and translocated similar amounts of 14C compared to the sethoxydim-sensitive goosegrass, these two mechanisms do not appear to be a means of tolerance. The major difference found between the two species was in the metabolism of sethoxydim. After 6 hours, 81% to 98% of the 14C in goosegrass extracts remained as 14C-sethoxydim. In contrast, only 1% of the 14C found in apical leaves, basal leaves, and roots of centipedegrass was identified as 14C-sethoxydim. These data indicated that differences in tolerance to sethoxydim between these two species were based on metabolism. Chemical name used: 2-[1-(ethoxyimino) butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2 -cyclohexen-1-one (sethoxydim).

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‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.] has a potential to become a new alternative warm-season putting green turfgrass. The main objective of the study was to determine factors affecting establishment speed for ‘Diamond’ zoysiagrass as a putting green in the southern transition zone of the United States. Two sprigging rates, three nitrogen (N) sources, two N rates, and two mowing heights (2.5 and 3.2 mm) were compared at Clemson University, Clemson, SC. Sprigs of ‘Diamond’ zoysiagrass were planted at rates of 91 or 182 m3·ha−1 in 2007 and repeated in 2008. Urea, ammonium nitrate, and ammonium sulfate were applied at 1.7 or 3.4 g N/m2/week from weeks after sprigging (WAS) 3 to 10. Rates were halved from WAS 11 to 16. The N fertilizers were applied as solutions weekly for 16 weeks. Weekly percent cover, turf color ratings, root and clipping sample, and ball rolling were collected for both years. A significant difference occurred in turf cover between high and low sprig rates. Turf color and cover results show that high rates of fertility associated with high rates of sprigs produced 100% turf cover at WAS 11 and 13 in both years. At the 2.5-mm mowing height, ball rolling reached 258 cm in August and was significantly faster than the 3.2-mm mowing height. Results show ‘Diamond’ zoysiagrass can be established within the same growing season to meet a playable putting green quality, but the establishment speed may vary depending on summer monthly temperature fluctuations.

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Drainage is important to golf and athletic facilities trying to avoid lost play time. Native soil containing clay is sometimes incorporated into sand profiles with the intent to increase water and nutrient holding capacities. However, mixes high in silt and/or clay often have drainage problems. Research was conducted on soil physical properties from incremental 10% v/v additions of silt and clay (fines) to a U.S. Golf Association (USGA)-specification sand. Soils were evaluated based on volumetric water retention from 0 to 50 cm matric potential, saturated hydraulic conductivity (Ksat), porosity, and bulk density. The soil water characteristic (SWC) for 100:0 (sand:fines) had lower volumetric water content (θv) throughout the profile than any other mixture. Addition of 10% fines increased θv to more than 0.17 cm3·cm–3 throughout the 0- to 50-cm matric potential range, whereas 20% fines increased θv to more than 0.26 cm3·cm–3. The 70:30 mixture had greater θv throughout the profile than mixtures containing more than 70% sand. Mixtures with less than 70% sand produced similar SWCs. Increasing sand content increased bulk density, which altered saturated volumetric water content. Ksat was reduced from more than 265 cm·h–1 in 100:0 mixtures to 43 cm·h–1 for 90:10 mixtures, and to less than 5 cm·h–1 with ≥20% fines. The addition of ≥20% by volume of fines to a USGA sand increased water content in the soil to the point it was rendered unacceptable for trafficked turf sites. This research illustrates the influence fine particles, even in small amounts, can have on a USGA sand, and why they should not be added without prior evaluation.

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Clarireedia jacksonii sp. nov. formerly Sclerotinia homoeocarpa F.T. Bennett, one of the causal agents of dollar spot, is the most widespread pathogen in turfgrass systems. Dollar spot (DS) affects both cool- and warm-season grasses, during a wide range of environmental conditions. Field studies were conducted at Clemson University, Clemson, SC, on a creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds) cv. Crenshaw] putting green for 2 consecutive years from August to October in year 1 and July to September in year 2. The objective of the studies was to evaluate biological control agents (BCAs) and synthetic fungicides at reduced rates for their efficacy controlling dollar spot. Four replications of 1.5 × 1.5-m plots were used in the experimental design. Treatments included the following: Bacillus subtilis (BS); plant extract oils (EO) including clove oil + wintergreen oil + thyme oil; extract of Reynoutria sachalinensis (RS); Bacillus licheniformis (BL); chlorothalonil (CL); and azoxystrobin + propiconazole (AzP). Synthetic fungicides were used at reduced rates in combination with biological control agents, to evaluate curative control efficacy of various combinations. All reduced synthetic programs, except CL + EO, provided acceptable disease severity (≤15%) at the end of year 1 and acceptable (≥7) turfgrass visual quality. Azoxystrobin + propiconazole, CL, AzP + BL, AzP + EO, AzP + BS all provided ≤15% disease severity and ≥7 visual turfgrass quality 14 days after the last application in year 2.

Open Access