Effects of preemergence herbicides on establishment of little bluestem and sideoats grama golf course rough

Abstract

AbstractNative warm‐season grass (NWSG) roughs provide environmental and aesthetic value to golf courses; however, weed competition is a constraint during establishment. This research evaluated the effects of common turfgrass preemergence herbicides on establishment of newly seeded 1:1 mixture of little bluestem [Schizachyrium scoparium (Michx.) Nash] and sideoats grama [Bouteloua curtipendula (Michx.) Torr.] (14.3 lb total seed acre−1) rough. Herbicides applied immediately after drill‐seeding included: atrazine (1.0 lb a.i. acre−1), dimethenamid‐P (1.5 lb acre−1), dithiopyr (0.38 lb acre−1), imazapic (0.06 lb acre−1), indaziflam (0.029 lb acre−1), isoxaben (1.0 lb acre−1), S‐metolachlor (2.48 lb acre−1), oxadiazon (4.0 lb acre−1), pendimethalin (1.47 lb acre−1), prodiamine (0.75 lb acre−1), and simazine (1.0 lb acre−1). Effects upon NWSG plant density and biomass, as well as smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.] control, were evaluated in 2017 and 2018. Across years, imazapic, dimethenamid, oxadiazon, and metolachlor controlled crabgrass >90%. In 2017, little bluestem plant density assessed 4 months after treatment was 2 to 13 times greater in imazapic‐treated plots than all other treatments except for those treated with isoxaben and simazine. Application of imazapic resulted in greater little bluestem aboveground biomass than all other herbicide treatments, except simazine, in 2017. In 2018, imazapic resulted in greater little bluestem plant density than the untreated control, atrazine, prodiamine, oxadiazon, isoxaben, or simazine. Although it was a minor component of the sward, sideoats grama was generally tolerant of imazapic. Imazapic application during seeded establishment of little bluestem and sideoats grama golf course rough provides acceptable crop tolerance and smooth crabgrass control.