This project highlights one component of a broader portfolio of center-funded research initiatives focused on developing novel approaches to complex scientific challenges.

Weed management in St. Augustinegrass is challenging due to sensitivity of this turfgrass to several postemergence (POST) herbicides. Due to enhanced stress tolerance, Sola St. Augustinegrass may demonstrate better tolerance to herbicides compared to Raleigh cultivar. A field study was conducted in Raleigh, NC in 2025 to evaluate the effect of ten POST herbicide treatments on turfgrass injury and cover of ‘Sola’ and ‘Raleigh’ St. Augustinegrass cultivars. The study was implemented as a two-factor factorial (cultivar and herbicide), and treatments were arranged in randomized complete block design (RCBD) with four replications. Herbicide treatment significantly affected turfgrass injury, with a premix of foramsulfuron + halosulfuron + thiencarbazone (Tribute Total), quinclorac (Drive XLR8), triclopyr (Triclopyr 4), and a premix of 2,4-D + dicamba + mcpp (Trimec Classic) caused unacceptable injury at 8 weeks after initial treatment (WAIT) (Figure 1). Sequential application of dicamba + fluroxypyr + mcpa premix (Change Up), dicamba + iodosulfuron + thiencarbazone premix (Celsius WG), fluazifop (Fusilade II) tank mixed with metcamifen + trifloxysulfuron (Recognition), mesotrione (Tenacity) and asulam (Asulox) caused minimal injury and can be used for weed control in St. Augustinegrass (Figure 1). Triclopyr (Triclopyr 4) and 2,4-D + dicamba + mcpp (Trimec Classic)-treated ‘Sola’ had at least 30% more green cover than ‘Raleigh’ St. Augustinegrass at 8 WAIT. St. Augustinegrass cultivars recovered from transient herbicide injury by 12 WAIT, except triclopyr-treated plots. St. Augustinegrass cultivars recovered from transient herbicide injury by 12 WAIT, except triclopyr-treated plots. Future research will evaluate these herbicide programs over additional growing seasons to validate the consistency of the current findings across temporal scales.

Bosc’s mille graines, a perennial broadleaf weed in the Rubiaceae family, has emerged as a significant management challenge in NC sod production fields. Bosc’s mille graines form dense mats through prolific tillering, reducing turfgrass aesthetics in lawns and sod quality. Other Rubiaceae weeds, such as poorjoe, Virginia buttonweed, etc. are difficult to control and often require sequential applications of synthetic auxin-based herbicide mixtures. However, information on how to achieve selective POST control of Bosc’s mille graines in turfgrass is not known. Two field studies were conducted in Council, NC in 2025 to assess POST Bosc’s mille graines control and turfgrass tolerance following sequential application of herbicide admixtures or premixes in St. Augustinegrass and zoysiagrass sod production fields. Trials were conducted at two sites – ‘Sola’ St. Augustinegrass site and ‘Empire’ zoysiagrass site, both heavily infested with Bosc’s mille graines. Treatments were arranged in a RCBD with four replications. Treatments included ten herbicide programs and a nontreated control, with all treatments applied sequentially at 4-week interval. Bosc’s mille graines control and density were affected by herbicide treatment but not by site or site by herbicide treatment interaction; therefore, data were pooled across both sites. By 12 WAIT, all treatments provided over control of 80% Bosc’s mille graines and reduced weed density by at least 88%, except dicamba + metsulfuron (Fahrenheit) and a premix of 2,4-D + carfentrazone + dicamba + dichlorprop (SpeedZone Southern). Turfgrass injury was transient, with no herbicide treatment effects on turfgrass by 10 WAIT. Sequential applications of a 2,4-D + dicamba + mcpp (Trimec Classic) admixture with carfentrazone (QuickSilver) effectively controlled Bosc’s mille graines with minimal injury to St. Augustinegrass. In zoysiagrass, either a 2,4-D + dicamba + mcpp premix (Trimec Classic) or admixture of 2,4-D + dicamba + mcpp (Trimec Classic) with carfentrazone (QuickSilver) provided effective Bosc’s mille graines control (Figure 2). Future research will focus on repeating the current study at additional sites and evaluating preemergence herbicide programs for Bosc’s mille graines control to develop season-long management strategies.