False-green kyllinga (kyllinga gracillima miq.) ecology and integrated managemnt strategies in cool-season turfgrass
Creators: name: Watson, Trevor Scott
Publisher: name: No Publisher Supplied
Year: 2024

description: False-green kyllinga (FGK; Kyllinga gracillima) is a common weed in cool-season turfgrass. Infestations can span across large areas and cause substantial turfgrass loss. Turfgrass practitioners will apply postemergence herbicides for FGK control, but efforts usually require sequential herbicide and overseeding applications. Although FGK infestations are especially prominent throughout the northeastern United States, there are few integrated management strategies that have been researched. Additionally, there is little known about the seedling competitiveness and the seedling response to preemergence herbicides used in cool-season turfgrass. The objectives of this research were to evaluate the establishment of FGK from seed in Kentucky bluegrass (Poa pratensis), evaluate the efficacy of preemergence herbicides used in cool-season turfgrass against FGK emergence from seed in soil, and to evaluate the impact of soil-applied nitrogen on effectiveness of single postemergence herbicide applications. The first experiment was conducted over a two-year period at one location in adjacent sites in New Jersey. This study evaluated the effects of two turfgrass density programs (high and moderate) and three weed seeding programs (FGK 5 and 500 kg ha-1 and smooth crabgrass (Digitaria ischaemum) at 500 kg ha-1) on FGK establishment. Seeding rates were designed to simulate a small infestation (5 kg ha-1) or a severe infestation (500 kg ha-1). Smooth crabgrass was included for comparison. The high turfgrass density program was designed to create a very dense stand of turf produced by high and moderate input programs, whereas the low density program was designed to produce a turf typical of a low low program. FGK establishment from seed was influenced more by turfgrass density than smooth crabgrass. Additionally, FGK re-established from rhizomes the after overwintering. Interestingly FGK cover was less affected by turfgrass density in the growing season after overwintering in one of two experimental runs. Most importantly, FGK established from seed in both high and low density turfgrass, reinforcing the need for further research in preemergence herbicides. A preliminary experiment was conducted over a two-year period at two locations in greenhouses in New Jersey and Indiana to evaluate the effects of 12 herbicides, two rates (100 and 10% of typical use rates for cool-season turfgrass) and two species (FGK and smooth crabgrass). Herbicides and 100% use rates included bensulide (11,200 g ha-1), corn gluten meal (880,000 g ha-1), dimethenamid (1,680 g ha-1), dithiopyr (560 g ha-1), isoxaben (1,120 g ha-1), mesotrione (280 g ha-1), methiozolin (516 g ha-1), oxadiazon (4,500 g ha-1), pendimethalin (3,360 g ha-1), prodiamine (840 g ha-1), siduron (13,500 g ha-1), and sulfentrazone (280 g ha-1). Dithiopyr, pendimethalin, and prodiamine were less effective against FGK than smooth crabgrass. Bensulide, dimethenamid, and oxadiazon were the most efficacious herbicides against both species at both locations. Further investigation conducted in a greenhouse in New Jersey involved seven herbicides (bensulide, dimethenamid, dithiopyr, isoxaben, oxadiazon, prodiamine, and sulfentrazone), six rates (100, 50, 25, 12.5, 6.3, 3.2% of typical use rate in cool-season turfgrass) and two species (smooth crabgrass and FGK). Bensulide, dimethenamid, and oxadiazon were the most effective herbicides (GR80 &lt; 4% of registered use rate) against FGK establishment from seed in both runs. Prodiamine and dithiopyr provided more smooth crabgrass control than FGK. To evaluate postemergence control with herbicides, a final experiment was conducted over a two-year period at two locations in New Jersey to evaluate a complete factorial of four nitrogen programs (0, 13, 25, 50 kg N ha-1), and three herbicide programs (sulfentrazone + carfentrazone at 280 + 30 g ha-1, halosulfuron at 70 g ha-1, and pyrimisulfan at 53 g ha-1) on herbicide effectiveness. At 52 weeks after treatment (WAT), halosulfuron application without nitrogen resulted in 70% FGK cover, whereas when 50 kg N ha-1 was added, cover decreased to 4%. Nitrogen did not affect FGK control from sulfentrazone + carfentrazone in either experiment. The effect of N on pyrimisulfan is unclear. In run 1 there was a non-significant tendency for pyrimisulfan efficacy to increase with N rate. In run 2, N applied at ≥13 kg decreased pyrimisulfan efficacy 12 WAT. Inconsistencies amongst treatments across years warrant a third experimental run planned for 2024. Results of the experiments suggest that practitioners should implement integrated management strategies that focus on maintaining a dense turfgrass stand and furthermore, it may be beneficial to use preemergence products such as bensulide, dimethenamid, and oxadiazon when controlling false-green kyllinga from seed in soil.