Zoysiagrass (Zoysia japonica Steud.) requires few inputs and provides high-quality turf in the transition zone, but is expensive to sprig or sod. Establishment by seed is less expensive than vegetative establishment, but little is known about renovation of existing turf to zoysiagrass using seed. Two experiments were performed to determine effects of herbicides and seeding rates on establishment of zoysiagrass in Indiana and Kentucky. In the first experiment, interseeding zoysiagrass into existing perennial ryegrass (Lolium perenne L.) without the use of glyphosate before seeding resulted in 2% zoysiagrass coverage 120 days after seeding (DAS). In plots receiving glyphosate before seeding, zoysiagrass coverage reached 100% by 120 DAS. In the second experiment, MSMA + dithiopyr applied 14 days after emergence (DAE) or MSMA applied at 14+28+42 DAE provided the best control of annual grassy weeds and the greatest amount of zoysiagrass establishment. Applying MSMA + dithiopyr 14 DAE provided 7% less zoysiagrass coverage compared to MSMA applied 14 DAE at one of the four locations. Increasing the seeding rate from 49 kg·ha-1 to 98 kg·ha-1 provided 3% to 11% more zoysiagrass coverage by the end of the growing season at 3 of 4 locations. Successful zoysiagrass establishment in the transition zone is most dependent on adequate control of existing turf using glyphosate before seeding and applications of MSMA at 14+28+42 DAE, but establishment is only marginally dependent on seeding rates greater than 49 kg·ha-1. Chemical names used: N-(phosphonomethyl) glycine (glyphosate); monosodium methanearsenate (MSMA); S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(triflurormethyl)-3,5-pyridinedicarbothioate (dithiopyr).
Preemergence (PRE) herbicides are used to control crabgrass (Digitaria spp.). Single spring applications are common in areas with relatively low crabgrass pressure, whereas sequential applications often are used to extend control in locations with high crabgrass pressure. Our objectives were to determine if changing a.i. in initial and sequential applications affects crabgrass control and if single spring applications of tank-mixed PRE herbicides provide season-long crabgrass control. Studies were conducted 2009, 2010, and 2011 in West Lafayette, IN, and 2011 in Wymore, NE. The PRE herbicides prodiamine, pendimethalin, and dithiopyr were tested using different application strategies. Sequential applications were applied mid-April and mid-June using all possible combinations of the three herbicides and untreated for the initial and sequential application. These herbicides also were applied mid-April as single full-rate PRE application or as a tank mixture of two PRE herbicides at half-plus-half or half-plus-quarter rate. Season-long crabgrass control was consistently achieved using sequential applications regardless which of the three herbicides was used for initial or sequential applications. Single applications of tank mixtures also provided consistent crabgrass control, equivalent to single full-rate applications of the individual PRE herbicides. Tank mixtures of half-plus-quarter rate and single half-rate applications resulted in more crabgrass cover than single full-rate or half-plus-half rate applications regardless of the herbicide applied.
Annual bluegrass (Poa annua L.) control with postemergence herbicides in cool-season turfgrass is often inconsistent. Amicarbazone and mesotrione have complementary modes of action but have not been evaluated in tank-mixtures for control of mature annual bluegrass in cool-season turfgrass. Field experiments were conducted during 2018 in New Jersey, and in Indiana, Iowa, and New Jersey during 2019 to evaluate springtime applications of amicarbazone and mesotrione for POST annual bluegrass control in cool-season turfgrass. On separate tall fescue (Festuca arundinacea Schreb.) and kentucky bluegrass (Poa pratensis L.) sites in 2018, three sequential applications of amicarbazone (53 g⋅ha−1) + mesotrione at 110 to 175 g⋅ha−1 provided >70% annual bluegrass control, whereas three sequential applications of amicarbazone alone at 53 and 70 as well as two sequential applications at 110 g⋅ha−1 provided <15% control at 14 weeks after initial treatment (WAIT). In 2019, results in New Jersey were similar to 2018 where amicarbazone alone provided less control than mesotrione + amicarbazone tank-mixtures. In Indiana, where the annual bluegrass infestation was severe and most mature, tank-mixtures were more effective than amicarbazone alone at 6 WAIT, but at 12 WAIT all treatments provided poor control. In Iowa, where the annual bluegrass infestation was <1 year old, all treatments provided similar control throughout the experiment and by >80% at the conclusion of the experiment. This research demonstrates that sequential applications of mesotrione + amicarbazone can provide more annual bluegrass control than either herbicide alone, but efficacy is inconsistent across locations, possibly due to annual bluegrass maturity and infestation severity.