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- Author or Editor: J.M. Goatley Jr. x
Research was conducted to evaluate crabgrass [Digitaria ischaemum (Schreb.) Muhl.] control, incidental dollar spot (incited by Lanzia and Moellerodiscus spp.) suppression, and turfgrass quality following sequential, low-level postemergence applications of DSMA to creeping bentgrass (Agrostis stolonifera var. palustris Farwell). DSMA was applied at 22 mg·m-2 at 7-day intervals for 15 consecutive weeks (DSMA-W) from May through Aug. 1986 and 1987 and for 10 consecutive weeks from June through Aug. 1988. DSMA also was applied in three split applications of 110 mg·m-2 every 10 days (DSMA-S) in June and July of each year. DCPA was applied in a single, preemergence application in May as a comparative standard for crabgrass control. Percent crabgrass in either DSMA-treated plot was 20% by 11 Sept., an infestation that was unacceptable for high-quality turf. Percent crabgrass infestation was 6% at all rating dates in 1987 or 1988 for DSMA-W and 11% at all dates in 1987 or 1988 for DSMA-S. DCPA significantly reduced percent crabgrass as compared to the nontreated control at all rating dates, but the percent crabgrass ratings tended to be higher than those for either DSMA treatment by the final rating dates of each year. The DSMA treatments significantly reduced dollar spot incidence in each year. Turfgrass discoloration was observed following the DSMA-S treatment in July 1987 as compared to the control, but the turf quality recovered by August. Turfgrass quality was higher for DSMA treatments than for either DCPA or the nontreated control due to season-long crabgrass control and disease suppression. Chemical names used: disodium methanearsonate (DSMA), dimethyl tetrachloroterephthalate (DCPA).
This study was conducted to determine if foliar-applied biostimulators could enhance harvestability and transplanting of Kentucky bluegrass (Poa pratensis L.) sod. The systemic triazole fungicides propiconazole at 42 mg·m-2 and triadimefon at 150 mg·m-2 enhanced post-transplant rooting and sod strength of bluegrass. Propiconazole had the best sod enhancement effect, increasing sod tensile strength 23% and increasing transplant root lift strength 64% across three experiments. The synthetic cytokinin benzyladenine (BA) at 6 mg·m-2 and seaweed extract (SWE, a freeze-dried extract of the seaweed Ascophyllum nodosum) at 0.3 ml product/m 2 had little effect. The response to triadimefon was intermediate. Foliar applications of chelated Fe phosphate citrate at 112 mg·m-2 did not enhance sod strength or rooting of Kentucky bluegrass when applied either alone or in combination with the biostimulator materials. Chemical names used: l-(2-(2,4 -dichlorophenyl)-4-propyl-l,3-dioxo1an-2-ylmethyl)-lH-l,2,4-triazole(propiconazole);1-(4-chlorophenoxy)-3,3-dimethyl-lH-(l,2,4-triazo1-l-yl)-butanone (triadimefon);6-benzylaminopurine (BA, benzyladenine).
This study was conducted to determine the potential anti-senescence activity of certain chemicals by monitoring changes in gross. CO2 exchange with senescence of excised leaves of Kentucky bluegrass (Poa pratensis L.). One day following foliar applications of benzyladenine (BA), triadimefon, and propiconazole, with and without chelated Fe (8% Fe phosphate citrate), Kentucky bluegrass leaves were excised, floated on distilled water in petri dishes, and placed in a darkened growth chamber. Gross CO2 exchange rates (CER) were recorded 1, 4, 7, and 10 days after excision (DAE). Foliar applications of Fe, BA, triadimefon, or propiconazole applied alone induced an anti-senescence response. Combinations of Fe with the chemicals delayed excision-induced leaf senescence, but no significant increase in anti-senescence activity was obtained from the Fe and chemical combinations as compared to the materials applied alone. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA); 1-(4-Chlorophenoxy)-3,3-dimethyl-1(1H-1,2,4-triazol-1yl)-2-butanone (triadimefon);1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole (propiconazole).
Bermudagrass turfs in the southern United States often receive late growing season applications of nitrogen (N) in order to sustain turfgrass color prior to dormancy, even though such applications might increase winterkill potential. Yearly research trials were initiated in the last week of Sept. 1989 to 1991 at Mississippi State Univ. to evaluate fall and spring color responses and rhizome levels of total nonstructural carbohydrates (TNC) of `Tiflawn' and Arizona (AZ) Common bermudagrass [Cynodon dactylon L. (Pers.)] treated with various N sources delivering N at 98 kg·ha-1 in a single application. The fertilizers were ammonium nitrate (AN), sulfur-coated urea (SCU), a natural organic (`Milorganite', NO), isobutylidene diurea (IBDU), ureaformaldehyde (UF), and methylene urea (MU). Color responses from N fertilization were most prominent in the fall except when there was an early frost event in Oct. 1990. The most rapid greening response and highest color ratings were consistently observed for the water-soluble AN. Of the slow-release sources, SCU, MU, and IBDU provided color responses as long as temperatures remained warm enough to promote bermudagrass growth. The NO source provided an unexpected, significant greening response in Oct. 1989 and 1991 on `Tiflawn', but not on AZ Common. The UF consistently provided the lowest color ratings. There were virtually no differences in TNC levels between N treatments for either grass. At no time was there any indication that N fertilization increased bermudagrass winterkill potential; to the contrary, the predominant responses were better fall and spring color than the nontreated control.
Research was conducted over 2 years to evaluate efficacy of various levels and combinations of imazaquin and AC 263,222 for growth regulation of unimproved bahiagrass (`Pensacola') turf. Imazaquin at 0.42 kg·ha–1 caused only slight bahiagrass discoloration in all trials and reduced seedhead count (as compared to the nontreated control) by ≥80% for 8 weeks after treatment (WAT) following a July 1992 application. AC 263,222 at 0.042 or 0.056 kg·ha–1 applied in late May or June provided 100% seedhead control through 8 WAT. However, AC 263,222 applied in July 1992 and Aug. 1993 at 0.056 kg·ha–1 resulted in unacceptable discoloration through 8 WAT. AC 263,222 at 0.014 or 0.028 kg·ha–1 provided ≥90% seedhead control with only minimal discoloration following applications in July or Aug. 1993, indicating that lower rates of AC 263,222 provided acceptable seedhead control of bahiagrass during times when growth was slowed due to moisture stress. Chemical names used: (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid (AC 263,222); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin).
A truly soilless turfgrass sod may be produced on kenaf-based (Hibiscus cannabinus L.) fiber mat that offers the integrity of field-cut sod without the use of mineral soil growing medium. This research was conducted to determine the feasibility of producing warm-season turfgrass sod on such a biodegradable organic mat. Seeded turfgrass plots contained 4.9 lb/1000 ft2 (24 g.m−2) of pure live seed planted on a 66-lb/1000 ft2 (325-g.m−2) organic fiber mat carrier placed atop either 66- or 132-lb/1000 ft2 (325- or 650-g.m−2) organic fiber mats. In an experiment using vegetative material, stolons were applied at rates of 16.4 ft3/1000 ft2 (0.82 L.m−2) over 132- or 198-lb/1000 ft2 (650- or 975-g.m−2) organic fiber mats and covered with a rayon scrim. All plots were placed on 6-mil black plastic. Nitrogen was applied at 0.9 lb/1000 ft2 (4.4 g.m−2) weekly in addition to a monthly micronutrient application. Bermudagrass (Cynodon σππ.) had quicker establishment than other grasses in the study, with stolonized and seeded plots achieving ≈100% coverage by 9 weeks in 1995 and 6 weeks in 1996, respectively. By 15 weeks after planting in 1995, the plot coverage ratings for seeded centipedegrass [Eremochloa ophiuroides (Munro) Hack. `Common'] and all stolonized grass plots of centipedegrass, zoysiagrass (Zoysia japonica Steud. `Meyer'), and St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze `Raleigh'] were 91% or higher. The results were much less favorable in 1996 than 1995 due to a later planting date and an irrigation failure.
A bioorganic fiber seeding mat was compared to traditional seeding into a prepared soil to ascertain any advantages or disadvantages in turfgrass establishment between the planting methods. Bahiagrass (Paspalum notatum), bermudagrass (Cynodon dactylon), carpetgrass (Axonopus affinis), centipedegrass (Eremochloa ophiuroides), st. augustinegrass (Stenotaphrum secundatum), and zoysiagrass (Zoysia japonica) were seeded at recommended levels in May 1995 and July 1996. The seeding methods were evaluated under both irrigated and nonirrigated conditions. Plots were periodically rated for percent turf coverage; weed counts were taken about 4 weeks after study initiation. Percent coverage ratings for all grasses tended to be higher for direct-seeded plots under irrigated conditions in both years. Bermudagrass and bahiagrass established rapidly for both planting methods under either irrigated or nonirrigated conditions. Only carpetgrass and zoysiagrass tended to have greater coverage ratings in nonirrigated, mat-seeded plots in both years, although the percent plot coverage ratings never reached the minimum desired level of 80%. In both years, weed counts in mat-seeded plots were lower than in direct-seeded plots. A bioorganic fiber seeding mat is a viable method of establishing warm-season turfgrasses, with its biggest advantage being a reduction in weed population as compared to direct seeding into a prepared soil.
Chlorsulfuron, diclofop, and sulfometuron were evaluated for potential use in selective control of tall fescue (Festuca arundinacea Schreb.) in Kentucky bluegrass (Poa pratensis L.). Polynomial trend analyses indicated highly significant linear and quadratic response curves for percentage of tall fescue reduction for each herbicide. Fall and spring treatments with chlorsulfuron and diclofop provided significant tall fescue control, with slight to moderate initial Kentucky bluegrass phytotoxicity. Fall and spring applications of sulfometuron resulted in excellent tall fescue control, but initial Kentucky bluegrass damage was severe and would be unacceptable for high maintenance turf. Chemical names used: 2-chloro- N -[[(4-methoxy-6-methyl-l,3,5-triazin-2-yl)amino]carbonyl]-benzenesulfonamide (chlorsulfuron); 2-[4-(2,4-dichlorophenoxy)phenoxy]proponoate (diclofop); N -[[(4,6-dimethylpyrimidin-2-yl)amino]carbonyl]-2-methoxycarbonyl-benzenesulfonamide (sulfometuron).
Laboratory studies were conducted to determine the basis for chlorsulfuron selectivity between Kentucky bluegrass (Poa pratensis L. cv. Kenblue) and tall fescue (Festuca arundinacea Schreb. cv. Rebel). Tall fescue absorbed and translocated more foliar-applied [14C]-labeled chlorsulfuron from the treated leaf than Kentucky bluegrass. The two species absorbed similar amounts of chlorsulfuron from nutrient solution into the roots, but tall fescue translocated more of the absorbed radioactivity to the shoots. Tall fescue metabolized chlorsulfuron in the shoots slightly more slowly than Kentucky bluegrass. Allof these factors apparently contributed to the higher tolerance of Kentucky bluegrass than of tall fescue to chlorsulfuron. Chemical name used: (2-chloro-N-[[4-methoxy-6-methyl-1,3,5 -triazin-2-yl)amino]-carbonyl] benzenesulfonamide) (chlorsulfuron).
Creeping bentgrass (Agrostis stolonifera) is used extensively on temperate zone golf course greens, tees, and fairways, but often performs poorly in shade. Previous research has indicated that sequential applications of gibberellic acid (GA) inhibiting plant growth regulators (PGRs) such as trinexapac-ethyl (TE) increase cool-season turfgrass performance in 70-90% shade. This research was conducted to: 1) confirm appropriate TE application rates and frequencies for maintaining `Penncross' creeping bentgrass in dense shade in the mid-Atlantic region of the U.S.; 2) determine the efficacy of other PGRs, biostimulants, and iron (Fe); and 3) assess whether the addition of a biostimulant with TE would have additive, synergistic, or negative effects. The other compounds tested against TE and the control were: propiconazole (PPC), iron sulfate, CPR (a seaweed and iron containing biostimulant), and a generic seaweed extract (SWE) (Ascophyllum nodosum) plus humic acid (HA) combination. These treatments were applied to 88% shaded bentgrass every 14 days from May or June through October in 2001 and 2002, with turf quality, leaf color, root strength, photochemical efficiency, and antioxidant enzyme superoxide dismutase (SOD) activity being determined. While the quality of control plots fell below a commercially acceptable level by the second month of the trial, repeated foliar TE application provided 33% to 44% better quality throughout the experiment. Propiconazole resulted in 13% to 17% better quality through September of each year. Trinexapac-ethyl and PPC resulted in darker leaf color and increased mid-trial root strength by 27% and 29%, respectively. Canopy photochemical efficiency and leaf SOD activity were also increased due to TE in August of both years. Treatment with Fe, CPR, or SWE+HA did not have an effect on quality, root strength, SOD, or photochemical efficiency, but periodic increases in color were observed. The addition of CPR to TE in 2002 provided results that were not different from those of TE-alone. This and previous studies indicate that restricting leaf elongation with anti-GA PGRs is of primary importance for improving shade tolerance, while treatments that increase leaf color or chlorophyll levels without restricting leaf elongation are relatively ineffective.