Aryloxyphenoxypropionate (AOPP) herbicides are used to control bermudagrass contamination in various turfgrasses. Applying AOPP herbicides alone can cause unacceptable injury to zoysiagrass but injury can be reduced when tank-mixed with triclopyr. There are limited data illustrating the extent of bermudagrass control and zoysiagrass cultivar tolerance when these compounds are combined. Research was conducted to determine the efficacy of multiple AOPP herbicides applied alone and tank-mixed with triclopyr for bermudagrass control in zoysiagrass turf. Treatments include three sequential applications of cyhalofop (0.32 kg ai ha−1), fenoxaprop (0.14 kg ha−1), fluazifop (0.11 kg ha−1), or quizalofop (0.09 kg ha−1) applied alone and tank-mixed with triclopyr (1.12 kg ae ha−1) applied to ‘Tifway’ bermudagrass, and ‘Diamond’, ‘Palisades’, and ‘Zenith’ zoysiagrass. Tifway bermudagrass control ranged from 41 to 69% and digital image analysis turf coverage data ranged from 18 to 50% for AOPP herbicides applied alone. The addition of triclopyr to AOPP herbicides increased bermudagrass control (64–79%) and reduced turf coverage (8–29%). Palisades and Zenith zoysiagrass exhibited less injury (1–18%) and greater turf coverage (84–86%) when AOPP herbicides were tank-mixed with triclopyr compared to AOPP herbicides applied alone. Diamond zoysiagrass was not tolerant to any AOPP herbicides applied alone or tank-mixed with triclopyr, except for fluazifop alone (18% injury and 93% turf coverage). Visual ratings and digital image analysis turf coverage data had a strong negative correlation over all tested turfgrasses. In general, AOPP herbicides plus triclopyr will control bermudagrass greater and injure zoysiagrass less compared to AOPP herbicides applied alone; however, these mixtures can cause unacceptable injury to Diamond zoysiagrass.

Realistic traffic simulation is crucial to the validity of athletic field research. Previously developed athletic field traffic simulators contain studded drums that turn at different speeds, creating shear forces at the playing surface. The Cady Traffic Simulator (CTS) (a modified walk‐behind core cultivation unit) was developed at Michigan State University in 2000. The objective of this study was to compare the magnitude and direction of the forces produced by two traffic simulators: the Brinkman Traffic Simulator (BTS), a pull‐behind unit, and the CTS. Both simulators were operated over an in‐ground force plate, which measured the forces in three directions: front to back, side to side, and vertical. The CTS produced a higher compressive stress and net shear stress when operated in either direction than the BTS. The average peak compressive stress produced by the feet of the CTS when operated in the forward direction was approximately 30 times higher than the combined compressive stresses of both BTS drums. The average peak net shear stress produced by the feet of the CTS when operated in the forward direction was approximately 15 times higher than the combined net shear stresses of both BTS drums. Operating in the reverse direction, the average peak compressive stress produced by the feet of the CTS was greater than five times the compressive stresses of both BTS drums combined. The average peak net shear stress produced by the feet of the CTS was approximately four times higher than the combined net shear stresses of both BTS drums.

Dinitroaniline‐resistant annual bluegrass (Poa annua L.) has been reported in several states; however, there are no standardized screening methods for detecting resistance. Research was conducted to evaluate screening techniques (Murashige and Skoog [MS] media, filter paper, hydroponics, and soil based) to detect herbicide resistance to dithiopyr, prodiamine, and pendimethalin in a suspected resistant ecotype of annual bluegrass from Chattanooga, TN (Chattanooga). A senstitive ecotype from Fresno, CA (Control) was also tested. All the bioassays were able to diagnose the ecotype from Chattanooga as resistant to prodiamine and pendimethalin. However, the degree of resistance was highly variable between bioassays. In hydroponics, the amount of prodiamine required to inhibit Chattanooga growth by 50% was 26 times more than Control. Comparatively, in MS media the amount of prodiamine required to inhibit Chattanooga growth by 50% was 80 times more than Control. Minor dithiopyr resistance from the Chattanooga ecotype was detected by the hydroponics, filter‐paper and soil‐based bioassays. Hydroponics provided the most rapid diagnosis of resistance, accessing resistance for a mature plant in 10 d. The MS‐media bioassay had the least amount of confounding variables. These findings highlight the potential variation in results that can occur in mitotic‐inhibiting herbicide resistance detection simply on the basis of how plant samples are assayed.

Data describing intraspecific differences in hybrid bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt Davy] traffic tolerance are linriited. Field research was conducted evaluating the effects of nnowing practices and perennial ryegrass {Lolium perenne L.) overseeding on the traffic tolerance of three hybrid and one improved common bermudagrass. Bermudagrass cultivars (Tifway', 'Patriot', 'Mississippi Choice', and 'Riviera') were subjected to mowing programs (reel mowing at 2.2 cm [RM] or RM plus grooming to a 1.9 cm depth [RMPG]) and perennial ryegrass overseeding (0 kg pure live seed [PLS] ha-1 or 593 kg PLS ha"^). Simulated traffic was applied twice weekly with a Cady traffic simulator. Percent green cover was measured after each simulated traffic event using digital image analysis. On >70% of evaluation dates, Tifway and Riviera yielded higher percent green cover compared to Patriot, while Mississippi Choice ranked intermediate. Reel mowing at 2.2 cm plus grooming to a 1.9 cm depth reduced percent green cover on the majority of rating dates in 2006; however, this response was not observed in 2007. Reel mowing at 2.2 cm plus grooming to a 1.9 cm depth did not reduce thatch accumulation either year. Reductions in bulk density and increases in green cover, thatch accumulation, and saturated hydraulic conductivity were associated with overseeding, suggesting that this practice may protect bermudagrass athletic fields from both components of traffic stress; wear and sou compaction.

Mesotrione is a carotenoid biosynthesis inhibiting herbicide, which is being evaluated for use in turfgrass. Carotenoids are important light harvesting and photoprotecting pigments that dissipate and quench excess light energy. The effects of mesotrione on carotenoid concentrations in turf and weed species, such as perennial ryegrass (Lolium perenne L.), are poorly understood. Mesotrione injury to perennial ryegrass has been reported, and symptomology may differ due to postapplication environmental factors such as irradiance and temperature. Research was conducted to investigate the effects of mesotrione on perennial ryegrass under varying irradiance (600, 1100, or 1600 micromol/m (2)/s) at three different temperatures (18, 26, and 34 degrees C). Postapplication irradiance and temperature levels did not affect visual injury symptoms in perennial ryegrass. Bleaching of treated plants was highest 7 days after treatment (DAT; 8%) and recovered to nontreated levels by 21 DAT. Mesotrione applications did not decrease perennial ryegrass foliar biomass accumulations. Carotenoid concentrations of nontreated plants were similar to those reported in creeping bentgrass and many green leafy vegetable crops. However, chlorophyll a and b, beta-carotene, lutein, and violaxanthin concentrations decreased due to mesotrione applications, while phytoene and zeaxanthin, a photoprotecting carotenoid, increased. The photochemical efficiency (F v/ F m) of treated plants was lower than nontreated plants at 3 and 7 DAT; however, treated plants recovered to nontreated levels 21 DAT. Results indicate that postapplication irradiance and temperature levels may not affect mesotrione efficacy in perennial ryegrass. Preferential accumulation of zeaxanthin following mesotrione applications may be a stress-related response, which may reduce light harvesting complex size and directly quench excess light energy.

New turfgrass varieties and management practices have introduced new options for transition zone athletic field managers. Our objectives were to determine the wear tolerance of four turfgrasses in the transition zone with and without crumb rubber under simulated athletic field conditions, and to determine if improved cool and warm‐season turfgrass species can be used for transition zone athletic fields. Field trials evaluated the use of four turfgrass species with and without crumb rubber topdressing in Knoxville, TN, and Fayetteville, AR. Experimental design was a randomized complete block with a split‐strip plot treatment arrangement. Plots containing ‘Thermal Blue’ hybrid Kentucky bluegrass (Poa pratensis L. × P. arachnifera Torr.) or ‘Riviera’ [Cynodon dactylon (L.) Pers.], ‘Quickstand’ (C. dactylon), or ‘Tifway’ (C. dactylon × C. transvaalensis Burtt‐Davy) bermudagrass were evaluated. Crumb rubber treatments were topdressed to achieve a 2‐cm depth. Traffic was applied to each plot using a Cady Traffic Simulator to simulate athletic field wear. Traffic applications coincided with actual fall athletic seasons ranging from October to December 2005. Hybrid Kentucky bluegrass proved to be acceptable for use in transition zone athletic fields, Riviera and Tifway showed comparable wear tolerance, and Quickstand showed the lowest wear tolerance of the varieties tested. Crumb rubber topdressing resulted in a significant increase in turfgrass wear tolerance, and a decrease in surface hardness, soil bulk density, and shear resistance.

The Brinkman Traffic Simulator (BTS) has been a useful tool to simulate sports field traffic. However, rate of traffic stress produced by the BTS, a pull‐behind unit with two differentially connected studded rollers, has been questioned. The Cady Traffic Simulator (CTS), a modified walk‐behind core cultivation unit, was developed and tested to potentially produce more aggressive traffic stress. A comparison study was initiated between the BTS and CTS to evaluate these simulators on a Kentucky bluegrass (Poa pratensis L.) stand. Playing surface data collected were surface hardness, traction, soil moisture, bulk density, porosity, and plant counts. Higher surface hardness, lower traction, and lower plant count values resulted when the CTS applied 10 passes per week (PPW) compared with other treatments. Surface hardness, traction, and bulk density values were statistically similar when the CTS applied 2 PPW, and BTS applied 10 PPW.

Secondary effects of strobilurin applications may improve creeping bentgrass tolerance to high temperature stress. This research evaluated the effects of two strobilurin fungicides on the rooting of ‘Penncross’ and ‘Penn A‐1’ creeping bentgrass (Agrostis stolonifera L.) managed under two irrigation regimes during high temperature conditions in a greenhouse. The light and frequent (LF) regime irrigated to 100% evapotranspiration daily, and the deep and infrequent (DI) regime irrigated at leaf wilt to a 30 cm depth. Plants were maintained in a greenhouse that averaged a maximum daily temperature of 31°C. Fungicide treatments were pyraclostrobin (556 g a.i. ha−1), pyraclostrobin + boscalid (431 + 288 g a.i. ha−1), azoxystrobin (610 g a.i. ha−1), and a nontreated control. Azoxystrobin reduced visual root length and root biomass of Penncross plants compared to nontreated plants. Root length, root length density, and root biomass of azoxystrobin‐treated Penn A‐1 plants were also lower than nontreated plants under LF irrigation. Pyraclostrobin increased the visual root length of both cultivars under DI irrigation, and resulted in Penn A‐1 plants exhibiting increased total root length, root surface area, root length density, root volume, and root biomass compared to nontreated plants. Changes in rooting were not associated with changes in turfgrass quality for either cultivar. Additional research is needed to determine if these responses are present following applications in the field.