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.

Much research has been conducted on mesotrione activity on crops and weeds, but information is lacking in regards to the relative contribution of soil and foliar absorption of mesotrione. Three experiments conducted at Virginia Tech's Glade Road Research Facility in Blacksburg, VA, evaluated the effects of 50 and 90% relative humidity (RH) on the activity of mesotrione applied to foliage, soil, and soil plus foliage. Tall fescue injury ranged from 0 to 21% and was significant in 6 of 20 comparisons. Three of these injury events were caused by soil plus foliar applications, which were always more injurious than foliar only applications, which were more injurious than soil-only applications. Both application placement and RH significantly influenced smooth crabgrass responses to mesotrione. Smooth crabgrass phytotoxicity was lowest when mesotrione was applied only to foliage and highest when mesotrione was applied to soil and foliage. Increasing RH from 50 to 90% caused a 4- to 18-fold increase in plant phytotoxicity when mesotrione was applied only to foliage. By dissecting the plant canopy, it was noted at 14 d after treatment, when averaged over RH, that white leaves comprise 16% of leaves when only foliage was treated and 55 and 62% when applied to soil plus foliage and soil only, respectively. Furthermore, white tissue was found predominately in the two youngest leaves when mesotrione was applied to soil or both soil and foliage, but in older leaves when applied only to foliage. Data indicate mesotrione entering plants through soil travels quickly to growing points and has an equal or greater effect on plant phytotoxicity than foliar-absorbed mesotrione. In addition, foliar-absorbed mesotrione appears to increase in plants significantly with increasing RH, but does not move rapidly to growing points.

Lolium perenne L. (perennial ryegrass) commonly contaminates Agrostis stolonifera L. (creeping bentgrass) on cool-season golf courses. Currently, few herbicide options are available for the selective control of L. perenne in A. stolonifera. Previous studies have indicated that flazasulfuron could be a potential solution, so trials were conducted at three sites in Blacksburg, VA to evaluate flazasulfuron rates and sequential treatments for L. perenne control and A. stolonifera response. Flazasulfuron applied once at 8.8 g a.i. ha −1 ; twice at 1.1, 2.2, and 4.4 g a.i. ha −1 ; and three times at 1.1 and 2.2 g a.i. ha −1 completely controlled L. perenne by 5 weeks after initial treatment (WAIT). Sulfosulfuron and bispyribac-sodium controlled L. perenne 68 and 35% 5 WAIT, respectively. All flazasulfuron treatments eliminated L. perenne cover, sulfofulfuron reduced cover from 34 to 11% at one site, and bispyribac-sodium did not influence cover 9 WAIT. All treatments generally caused up to 10% A. stolonifera injury within one week of each treatment but only flazasulfuron at 4.4 g a.i. ha −1 and sulfosulfuron caused unacceptable and persistent injury. Flazasulfuron applied in sequence at rates of ≤2.2 g a.i. ha −1 causes mild and transient discoloration of A. stolonifera but completely controls L. perenne.

Mesotrione typically requires multiple applications to control emerged weeds in turfgrass. Since it is absorbed by both foliage and roots, a controlled-release (CR) formulation could eliminate the need for multiple applications. Research was conducted evaluate simulated-release scenarios that mimic a potential CR mesotrione formulation. A soluble concentrate formulation of mesotrione was titrated to produce a stepwise change in mesotrione rates, which were applied daily to mimic predetermined release scenarios over a three-wk period. CR scenarios were compared to a broadcast treatment of mesotrione at 280 g ai ha-1 applied twice at three-wk intervals, and a nontreated. Mesotrione applied in three temporal release scenarios controlled creeping bentgrass, goosegrass, nimblewill, smooth crabgrass, and white clover equivalent to the standard sprayed mesotrione treatment in every comparison. However, each CR scenario injured tall fescue 2 to 7 times more than the standard treatment. Soil- and foliar-initiated repeat treatments were equivalent in most comparisons. Data indicates that mesotrione applied in a temporal range to simulate controlled release scenarios can deliver desired weed control efficacy comparable to sequential broadcast applications. More research is needed to elucidate proper timings and release scenarios to minimize turfgrass injury.