False-green kyllinga is a problematic C4 perennial Cyperaceae species. Previous research examined herbicide efficacy but has not integrated nonchemical practices with herbicides. Replicate field experiments were conducted to evaluate late-summer postemergence applications of herbicides in combination with turf-type tall fescue interseeding for false-green kyllinga control. Seven herbicide treatments and a nontreated control formed a complete factorial, with tall fescue interseeding or no seeding (eight-by-two factorial). Six herbicide treatments consisted of single postemergence applications of halosulfuron-methyl (70 g ha–1), imazosulfuron (420 g ha–1), and sulfentrazone + carfentrazone (280 + 30 g ha–1) applied 4 wk before tall fescue interseeding (WBS) and the day of interseeding. Glyphosate (220 g ae ha–1) applied the day of interseeding was the seventh herbicide treatment. Tall fescue was interseeded in September, and false-green kyllinga control was evaluated the following summer. In combination with tall fescue interseeding, imazosulfuron and halosulfuron applied 4 WBS as well as glyphosate applied the day of interseeding controlled false-green kyllinga better than all other treatments. In July, imazosulfuron and halosulfuron treatments applied 4 WBS and combined with interseeding had 1% to 6% false-green kyllinga cover, respectively, compared to 28% and 62% cover, respectively, without interseeding. Interseeding alone controlled false-green kyllinga <50%. Imazosulfuron, halosulfuron, and sulfentrazone + carfentrazone applied the day of seeding severely injured emerging tall fescue seedlings and reduced turfgrass quality the following spring. Applying imazosulfuron or halosulfuron in late summer and interseeding turf-type tall fescue 4 wk later or applying glyphosate the day of seeding are effective strategies for postemergence false-green kyllinga control. Integrating herbicides and the cultural practice of tall fescue interseeding provided more false-green kyllinga control than either practice alone.

Recent research reported synergism between glufosinate plus very low rates of protoporphyrinogen oxidase (PPO)–inhibiting herbicides on select broadleaf weeds. Two field studies, each consisting of four trials, were conducted in 2020 and 2021 in commercial fields with glyphosate-resistant (GR) horseweed in Ontario, Canada. Study 1 evaluated GR horseweed control with glufosinate plus five PPO inhibitors at 5% of the label rate; study 2 evaluated what dose of saflufenacil is needed when co-applied with glufosinate to improve GR horseweed control. In study 1, glufosinate plus very low rates of PPO-inhibiting herbicides provided low GR horseweed control. At site 1, despite the synergistic increase in GR horseweed control with saflufenacil (1.25 g ai ha–1) plus glufosinate (300 g ai ha–1), the level of control did not exceed 42% at 2 and 4 wk after application (WAA); the interaction was additive at 8 WAA. The co-application of glufosinate (300 g ai ha–1) with pyraflufen-ethyl (0.34 g ai ha–1), pyraflufen-ethyl/2,4-D (26.4 g ai ha–1), flumioxazin (5.35 g ai ha–1), fomesafen (12 g ai ha–1), or sulfentrazone (7 g ai ha–1) resulted in an additive interaction for GR horseweed control at 2, 4, and 8 WAA. However, glufosinate plus pyraflufen-ethyl or sulfentrazone was antagonistic at 8 WAA. In study 2, similar doses of saflufenacil were required for 50%, 80%, and 95% GR horseweed control whether glufosinate was included in the mixture or not. Interactions between glufosinate (300 g ai ha–1) plus saflufenacil at 1.56, 3.13, 6.25, and 12.5 g ai ha–1 were antagonistic at 2, 4, and 8 WAA at sites 1, 2, and 3; all other interactions were additive. The results of this research indicate there was little to no benefit of adding very low rates of PPO-inhibiting herbicides to glufosinate to improve GR horseweed control under field conditions.

We conducted research to evaluate various herbicides for POST false-green kyllinga control in cool-season turfgrass (primarily creeping bentgrass). In a preliminary evaluation, single and sequential applications of halosulfuron-methyl (70 g ai ha−1), mesotrione (175 g ai ha−1), and sulfentrazone (140 g ai ha−1), as well as a single application of imazosulfuron (740 g ai ha−1), were evaluated in New Jersey. Imazosulfuron and sequential applications of halosulfuron-methyl controlled false-green kyllinga >93% at 9 and 18 wk after initial treatment (WAIT). Sulfentrazone and mesotrione controlled false-green kyllinga <50%. Additional experiments were conducted to evaluate single and sequential applications of halosulfuron-methyl (70 g ha−1), imazosulfuron (420 and 740 g ha−1), and sulfentrazone (140 g ha−1) in New Jersey and Indiana at two locations in each state. At 12 WAIT, imazosulfuron generally controlled false-green kyllinga more effectively than other treatments at all locations. Sequential applications of imazosulfuron controlled false-green kyllinga 100% at 12 WAIT. Halosulfuron-methyl was less effective in Indiana than in New Jersey. Sulfentrazone controlled false-green kyllinga <40% at 12 WAIT. This research demonstrates that imazosulfuron is more effective than halosulfuron-methyl and sulfentrazone for POST false-green kyllinga control in cool-season turf.