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Warm-season turfgrass quality declines under shade due to reduced photosynthesis, increased disease pressure, reduced carbohydrate production, tree root competition, and reduced lateral stem growth. Another factor limiting turfgrass growth and development under tree shade is variable qualities of light fi ltered by trees. However, effects of various fi ltered wavelengths on turfgrass performance are lacking and deserve research. Therefore, a greenhouse project investigated the physiological and morphological responses of ‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.], ‘Sea Isle 2000’ seashore paspalum (Paspalum vaginatum Swartz.), and ‘Tifway’ and ‘Celebration’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] to variable light spectral qualities. Light treatments included a control without any shade cloths and four different color shade cloths fi ltering wavelengths 560 to 720 nm (blue shade cloth), 360 to 520 nm (yellow shade cloth), 360 to 560 nm (red shade cloth), and 360 to 720 nm (black shade cloth). The percent light reduction for each cloth was about 65% relative to the control. Data collected included visual turfgrass quality (TQ), relative clipping yield, relative chlorophyll concentration, relative shoot width, relative root biomass, relative root length density, relative specifi c root length, and root and shoot total nonstructural carbohydrates. Diamond was the least affected turfgrass by the color shade cloths, while Celebration and Sea Isle 2000 performed similarly. Tifway was the most sensitive turfgrass with the lowest TQ under color shade cloths. Yellow and red shades were least detrimental, while black shade most negatively inhibited parameters measured, followed by blue shade. This study implies different types of shade signifi cantly impact the TQ of warmseason turfgrasses.

Dwarf bermudagrass (Cynodon dactylon x C. transvaalensis Burtt-Davy) and creeping bentgrass (Agrostis stolonifera L.) are planted for golf greens in the U.S. transition zone, but management regimes, such as the use of a plant growth regulator (PGR), often vary for long-term culture of the two species. The objective of this experiment was to investigate application regimens of the PGR trinexapac-ethyl (TE), on growth, quality, and performance of creeping bentgrass and bermudagrass putting greens in Clemson, SC. 'L-93' creeping bentgrass and 'TifEagle' bermudagrass putting greens, established in summer 2002 and mowed at 3.2 mm, received TE over 12 wk in three regimens: 0.017 kg ha 1 wk -1 , 0.033 kg ha) -1 2 wk -1 (biweekly), or 0.05 kg ha -1 3 wk -1 (triweekly) from May to August 2003 and 2004. Creeping bentgrass was not discolored from TE, but unacceptable bermudagrass discoloration (>20%) occurred on one, two, and six dates for weekly, biweekly, and triweekly regimens, respectively. All TE regimens reduced bermudagrass clippings approximately 50% from nontreated bermudagrass across all dates, while creeping bentgrass clipping reductions, approximately 20 to 35% from nontreated grass, were inconsistent. The root masses of both species treated with TE regimens were similar to nontreated turf. Bermudagrass aerification recovery was reduced on two, two, and four dates after weekly, biweekly, and triweekly TE regimens, respectively. All TE regimens increased morning and evening bermudagrass golf ball roll distance approximately 25 cm from morning distances of nontreated turf.

Plant growth regulators (PGRs) improve turf color by inhibiting leaf growth and may reduce fertilization requirements of bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt-Davy] golf greens by reducing nutrients removed through clipping collection. To test this hypothesis, growth, color, and nutrient allocation of 'TifEagle' bermudagrass maintained at 3.2 mm were investigated in field experiments conducted in Clemson, SC, from April to August in 2003 and 2004. Ammonium nitrate was applied at 6,12,18, or 24 kg N ha -1 wk -1 with a PGR, trinexapac-ethyl {[4-(cydopropyl-[α]-hydroxymethylene)- 3,5-dioxo-cydohexane carboxylic add ethyl ester]) (TE), at 0 or 0.05 kg a.i. ha -1 3 wk -1 . Turf required 18 to 24 kg N ha -1 wk -1 from May to June and ≤12 kg N ha -1 wk -1 from July to August to maintain acceptable color (≥-7, 1-9 scale). Trinexapac-ethyl initially caused discoloration but bermudagrass recovered and had color enhanced 10 to 25% from nontreated. Trinexapac-ethyl reduced clippings 67% from nontreated while clippings, percentage of lateral regrowth, and aerification recovery increased with N rate. Bermudagrass treated with TE had similar root mass to nontreated but 5% greater stolon and rhizome mass, 18% higher chlorophyll concentration, up to 67% reduced lateral regrowth, and up to 38% reduced aerification recovery. Trinexapac-ethyl reduced leaf N, P, K, Mg, S, and Fe concentrations 10 to 25% and increased rhizome concentrations 8 to 36%. Nutrients recovered through clippings were reduced ≈70% from TE applications while TE-treated turf had increased N, P, K, Ca, Mg, S, Mn, and Fe retention in stolons and rhizomes. Overall, TE enhanced color while redudng nutrient translocation from rhizomes to leaves, thus increasing bermudagrass nutrient retention.

Excessive (>1.3 cm) thatch and mat layering of turfgrass is considered undesirable because it reduces hydraulic conductivity, water infiltration, increases localized dry spots and pest problems, and reduces pesticide effectiveness and turf tolerance to temperature extremes. The objective of this 2-yr study was to determine the efficacy of topdressing alone and in combination with several mechanical and biological methods to control thatch-mat accumulation in a newly established 'L-93' creeping bentgrass [Agrostis stolonifera L. var palustris (Huds.) Farw.] sand-based golf green. Mechanical and biological methods included vertical mowing at various depths and timings, core cultivation, grooming, a biological thatch control agent (Thatch-X), and combinations of core cultivation with grooming, core cultivation with vertical mowing, and core cultivation combined with grooming and vertical mowing. No treatment prevented thatch-mat accumulation, and thatch-mat depth for all treatments were similar to, or greater than, the untreated at the end of the study. Increases in percent organic matter content during the study ranged from 53% for core cultivation combined with grooming and vertical mowing to 123% for the untreated. Combinations of core cultivation plus vertical mowing with or without grooming were the most effective at minimizing thatch-mat accumulation. These treatments decreased percent organic matter 38 and 45%, respectively, compared with the untreated. Surface hardness was reduced an average of 19% by treatments that included core cultivation, and the cultivation treatments increased water infiltration rates an average of 58% in 2001 and 188% in 2002 compared with the untreated. Turf quality was not adversely affected by any management practice and remained acceptable (greater than or equal to 7.0) throughout the study.

St. Augustinegrass [(Stenotaphrum secundatum (Walt.) Kuntz.] is the preferred warm-season turfgrass for Florida's commercial and residential landscapes with an estimated 0.7 million hectare under growth and management. Limited published information is available on St. Augustinegrass response to plant growth retardants (PGRs). A 2-yr study was implemented to monitor St. Augustinegrass turf quality, lateral stolon growth, percent cover, mowing frequency, cumulative turfgrass clippings, and seedhead suppression following PGR application. Treatments were applied on 23 June 1995 and 22 June 1996 as a single application (SIA) at label use rate (LUR) or as twin split applications (TSA) at half LUR each: the sequential application was only used when mowing interval equaled the untreated. The PGRs and rates were flurprimidol [α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl]-5-pyrimidine-methanol] and paclobutrazol [(+/-)-(R*,R*)-β-[(4-chloro-phenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol] at 1.12 kg ha -1 for SIA and 0.56 kg ha -1 for TSA, trinexapac-ethyl [4-(cyclopropyl-α-hydroxymethylene)-3,5-dioxocyclohexane carboxylic acid ethylester] and mefluidide [N-[2,4-dimethyl-5-[[trifluoromethyl)sulfonyl]amino]phenyl]acetamide] at 0.28 kg ha -1 for SIA and 0.14 kg ha -1 for TSA, and imazapic [(±)-2-[4,5-dihydrol-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridine-carboxylic add] at 0.028 kg ha -1 for SIA and 0.014 kg ha -1 for TSA. Responses were observed for a 12-wk period following initial application, and turf quality was acceptable (>7) for all PGRs. Turf quality for imazapic was generally better than the untreated for Weeks 6 to 10. Greatest control of lateral stolon growth 10 wk after initial application was achieved with TSA of imazapic (68%) and mefluidide (61%). Percent cover 12 wk after initial application was lowest for SIA and TSA imazapic (66 and 53%, respectively). Greatest reduction in mowing frequency was provided by trinexapac-ethyl (50%), while flurprimidol and mefluidide reduced mowing frequency by 26 and 20%, respectively. The only PGR that reduced cumulative turfgrass clippings (CTC) was trinexapac-ethyl (63%). Greatest seedhead inhibition during peak production (about 35%) was provided by imazapic and mefluidide. The two most effective PGRs were trinexapac-ethyl (reduced mowing frequency and CTC) and imazapic (controlled lateral stolon growth and seedhead production), while mefluidide demonstrated some potential. Combinations of these products could be examined in future studies.