Dollar spot, caused by Sclerotinia homoeocarpa, is a severe disease of highly maintained turfgrass. Improving the efficacy of fungicides when applied in relatively low water volumes may be possible through the optimization of nozzle selection. The objectives of this research were to evaluate fungicide efficacy when delivered through five different nozzle types and to elucidate any potential interactions between fungicide mode of activity and nozzle type. Research was conducted at four locations in Pennsylvania and Connecticut in 2005. Chlorothalonil (contact mode of activity) and propiconazole (acropetal penetrant mode of activity) were applied alone or tank-mixed and delivered through five different nozzles. At all sites, no fungicide-by-nozzle interactions were observed, and dollar spot suppression was generally greatest when fungicides were tank-mixed. The TurfJet 1/4TTJ04 nozzle generally provided the poorest level of control when compared with all other nozzles (i.e., Air Induction AI11004, Turbo TeeJet TT11003, and XR TeeJet XR11003 or XR11004). Although the impact of nozzle type was not as pronounced under low to moderate disease pressure, nozzles that produce fine to coarse water droplets (i.e., Turbo TeeJet or XR TeeJet) or the Air Induction (AI) nozzle were associated with the best suppression under severe dollar spot pressure. Despite producing a very coarse droplet, the AI nozzle also facilitated excellent suppression of dollar spot under severe disease pressure. The use of AI-type nozzles may improve the efficacy of fungicides used to control foliar diseases while at the same time minimize the potential for drift to off-site targets.
John E. Kaminski and Michael A. Fidanza
Yu Huang, John E. Kaminski, and Peter J. Landschoot
Dollar spot, caused by Sclerotinia homoeocarpa F.T. Bennett, is an important disease of creeping bentgrass (Agrostis stolonifera L.) on golf courses in the northern United States. Canopy moisture in the form of dew plays an important role in the development of dollar spot and routine displacement has been shown to reduce disease severity. The use of plant growth regulators (PGRs) is a common management practice for maintaining creeping bentgrass fairways, but their influence on dollar spot is unclear. The objective of this field study was to elucidate the influence of dew removal at the time of fungicide application on dollar spot control in creeping bentgrass regulated by trinexapac-ethyl (TE). Main factors in the study included three dew removal strategies (non-treated, dew removed–mowed, and dew removed–not mowed) before the application of four fungicide treatments (non-treated, chlorothalonil, propiconazole, and iprodione). All fungicide treatments were applied once to turfgrass previously treated with TE or not treated. The presence or absence of dew at the time of fungicide application generally had no influence on fungicide performance with respect to dollar spot control. Based on the results of this study, dew removal before the application of fungicides targeting dollar spot is unnecessary. Applications of TE before fungicides reduced dollar spot severity in some cases, but reductions in symptom expression were limited and did not result in markedly improved dollar spot control.
John E. Kaminski, Peter H. Dernoeden, and Cale A. Bigelow
The tolerance of creeping bentgrass (Agrostis stolonifera L.) seedlings to many herbicides has not been evaluated. Three field studies were conducted between fall and spring from 1998 to 2002 to assess creeping bentgrass seedling tolerance to five herbicides and paclobutrazol. The primary objectives of this investigation were to assess bentgrass tolerance to these chemicals when applied at various timings following seedling emergence, and establishment of new seedlings as influenced by potential soil residues in the spring following a fall application of the chemicals. Treatments were applied 2, 4, or 7 weeks after either `Crenshaw' or `L-93' creeping bentgrass seedlings had emerged. Siduron (6.7 and 9.0 kg·ha-1) and bensulide (8.4 kg·ha-1) were noninjurious when applied two weeks after seedling emergence (2 WASE). Bensulide (14 kg·ha-1), ethofumesate (0.84 kg·ha-1), prodiamine (0.36 kg·ha-1) and paclobutrazol (0.14 kg·ha-1) were too injurious to apply 2 WASE, but they were generally safe to apply at 4 WASE. Chlorsulfuron (0.14 kg·ha-1) was extremely phytotoxic to seedlings when applied 2 WASE. Plots were treated with glyphosate and overseeded the following spring. The overwintering soil residuals of prodiamine and bensulide (14.0 kg·ha-1) unacceptably reduced spring establishment. All other herbicides and paclobutrazol had little or no adverse residual effects on spring establishment. Chemical names used: N-(phosphonomethyl)gycline (glyphosate); (±)-(R*,R*)-beta-[(4-chlorophenyl)methyl]-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol); 2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); S-(0,0-diisopropyl phosphorodithioate) ester of N-(2-mercaptoethyl) benzenesulfonamide (bensulide); [1-(2-methylcyclohexyl)-3-phenylurea] (siduron); N3,N3-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); 2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl] benzenesulfonamide (chlorsulfuron).
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.
Peter H. Dernoeden, John E. Kaminski, and Jinmin Fu
Creeping bentgrass (Agrostis stolonifera L.; CBG) is a common weed in home lawns and golf course roughs in many regions of the United States. Currently, no herbicides are registered for selective control of CBG in cool-season grasses. The objective of this field study was to evaluate the ability of mesotrione and triclopyr ester to selectively remove CBG from Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.). Mesotrione (0.14 and 0.21 kg·ha−1 a.i.) and triclopyr ester (0.56 and 1.12 kg·ha−1 a.i.) were applied on a 2-week interval two, three, or four times in Connecticut and Maryland in 2005, and three or four times in Maryland in 2006. Two applications of mesotrione at 0.21 kg·ha−1 a.i. provided marginally acceptable CBG control, but three or four applications at 0.14 or 0.21 kg·ha−1 a.i. provided excellent CBG control. Mesotrione elicited little or no injury to Kentucky bluegrass, but generally caused objectionable injury in tall fescue for about 7 to 14 d after each application. Triclopyr applied at 0.56 kg·ha−1 a.i. reduced CBG cover, but the level of control generally was unacceptable, regardless of application frequency. Three or four applications of triclopyr (1.12 kg·ha−1 a.i.) effectively controlled CBG in Connecticut in 2005 and Maryland in 2006. Triclopyr caused no visual injury to tall fescue, regardless of rate or application frequency. Four triclopyr applications to Kentucky bluegrass, however, were phytotoxic and reduced stand density, especially at the high rate (1.12 kg·ha−1 a.i.). Three summer applications of mesotrione (0.14 kg·ha−1 a.i.) or triclopyr (1.12 kg·ha−1 a.i.) provided the best combination of turfgrass safety and CBG control. Chemical names used: [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr ester); 2-[4-(methylsulfonyl)-2-nitrobenzoyl]-1,3-cyclohexanedione (mesotrione)
Peter H. Dernoeden, Steven J. McDonald, and John E. Kaminski
Establishing creeping bentgrass [Agrostis stolonifera L. (CBG)] and perennial ryegrass [Lolium perenne L. (PRG)] from seed can be hampered by competition from annual bluegrass (Poa annua L.). Bispyribac-sodium (BPS) is a postemergence annual bluegrass herbicide that may have applications for use when establishing these grasses. This field study was undertaken to determine if BPS could be applied safely to CBG and PRG seedlings. Ethofumesate (ETHO) was applied sequentially (840 + 840 g·ha−1 a.i.) and served as a standard. In 2004, BPS was applied once (49, 74, 111, and 148 g·ha−1 a.i.) or sequentially (49 + 49 and 74 + 74 g·ha−1 a.i.) to CBG and PRG seedlings 4 weeks after emergence in Maryland. In 2004, BPS discolored CBG and PRG and reduced PRG cover, whereas ETHO reduced CBG cover but was not injurious to PRG. In 2005, a single (148 g·ha−1 a.i.) and sequential (25 + 25, 49 + 49 and 74 + 74 g·ha−1 a.i.) applications of BPS were made to CBG and PRG 2 and 4 weeks after seedling emergence (WASE) in Maryland and Connecticut. Treatments applied 2 WASE generally resulted in more injury when compared with applications made 4 WASE. In Maryland in 2005, CBG only sustained long-term loss of cover when treated 2 WASE with 148 g·ha−1 a.i. of BPS. The PRG was more sensitive to BPS and 148 g·ha−1 a.i. applied once and sequential treatments 49 g·ha−1 a.i. or greater applied 2 and 4 WASE generally caused the greatest loss in PRG cover. Conversely, CBG was severely injured by all BPS treatments and ETHO in Connecticut. In PRG, only 25 + 25 g·ha−1 a.i. of BPS and ETHO in both timings did not cause a loss in cover in Connecticut or Maryland. High levels of precipitation and probably other unknown factors may have enhanced the phytotoxicity observed in Connecticut. Ethofumesate generally was safer than BPS for use on PRG seedlings.
Peter H. Dernoeden, Cale A. Bigelow, John E. Kaminski, and John M. Krouse
Smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Muhlenb.] is an invasive weed of cool-season turfgrasses. Previous research has demonstrated that quinclorac is an effective postemergence herbicide for crabgrass control, but performance has been erratic in some regions. Furthermore, quinclorac may elicit objectionable levels of discoloration in creeping bentgrass (Agrostis stolonifera L.). The objectives of this 3-year field study were to determine optimum rates and timings of quinclorac applications that provide consistent levels of effective crabgrass control and to assess creeping bentgrass quality responses to quinclorac. To evaluate crabgrass control, quinclorac was applied in early-, mid- and late-postemergence timings at various rates to a perennial ryegrass (Lolium perenne L.) turf. Similar treatments were applied to creeping bentgrass to determine if application timing and rate influenced the level and duration of discoloration. Quinclorac was applied alone or was tank-mixed with either urea (N at 6.1 kg·ha-1) or chelated iron (Fe)+nitrogen (N) (FeSO4 at 1.1 kg·ha-1+N at 2.2 kg·ha-1) to determine if they would mask discoloration. Crabgrass control generally was more effective in the early- and midpostemergence application timings. A single application of quinclorac (0.84 kg·ha-1) was effective where crabgrass levels were moderate, but sequential (i.e. multiple) applications were required where crabgrass levels were severe. The most consistent level of crabgrass control where weed pressure was severe occurred with three, sequential quinclorac (0.37 or 0.42 kg·ha-1) applications. Creeping bentgrass exhibited 2 to 11 weeks of unacceptable discoloration in response to sequential quinclorac applications. Chelated Fe+N was more effective than urea in masking discoloration. In general, chelated Fe+N tank-mixed with quinclorac masked discoloration and turf had quality equivalent to untreated bentgrass on most, but not all rating dates. Chemical names used: 3,7,-dichloro-8-quinolinecarboxylic acid (quinclorac).
John E. Kaminski, Tim T. Lulis, and Travis R. Russell
Equipment with hydraulic implements are often used to maintain turfgrass surfaces. Hydraulic implements can malfunction and lead to leaks or spills of hydraulic fluid, which is phytotoxic to turfgrass. Previous research has documented extensively hydraulic fluid injury on warm-season turfgrasses, but these effects have not been evaluated on cool-season grasses and warrant further investigation. Therefore, the objectives of this study were to compare phytotoxicity of petroleum, vegetable, and synthetic hydraulic fluids on a creeping bentgrass (Agrostis stolonifera) putting green and to evaluate the influence of postapplication remediation practices on reducing turfgrass injury. Turfgrass injury was evaluated over a 4-week period in 2011 and 2012 after simulated hydraulic fluid leak and remediation practices were applied. Complete necrosis was observed after 28 days for all hydraulic fluid types. However, water rinse (RO) or detergent soap solution drench followed by brushing in/water rinse (SBR) remediation practices effectively eliminated turfgrass injury by the end of the 4-week period for synthetic polyalkylene glycol fluid treatments, but no other hydraulic fluid types. Turfgrass managers might consider the synthetic polyalkylene glycol hydraulic fluid tested in this study as a less phytotoxic alternative to petroleum hydraulic fluids if a remediation practice is implemented after a leak or spill.