Converting cool-season golf course fairways to creeping bentgrass (Agrostis palustris Huds.) is desirable because it affords excellent playability, enhanced recuperative potential, and enhanced disease tolerance compared to annual bluegrass (Poa annua sp. Timm.) or perennial ryegrass (Lolium perenne), which are common species in fairways. However, converting current golf course fairways to creeping bentgrass with nonselective herbicides is problematic because it disrupts play and decreases revenue, as fairways must be closed for an extended period of time. The objective of our study was to quantify the effect of trinexapac-ethyl (TE), overseeding date, and overseeding rate on the success on the gradual conversion of cool-season fairways to creeping bentgrass over 3 years. `Penneagle' creeping bentgrass was overseeded at 0, 49, or 98 kg·ha-1 in fall, spring, or fall+spring after aerification, and application of TE at 0.0, 0.2, or 0.4 kg·ha-1. Gradual conversion to creeping bentgrass was effective, on perennial ryegrass fairways, with up to 36% cover of creeping bentgrass after 3 years of overseeding. However, only a maximum of 3% creeping bentgrass cover was obtained after the third year of overseeding into primarily annual bluegrass fairways. Fall overseeding with bentgrass at 49 or 98 kg·ha-1 was equally effective and additional spring overseeding did not improve establishment. Applications of TE prior to overseeding did not enhance the conversion. Chemical name used: 4-cyclopropyl-a-hydroxy-methylene-3,5-dioxocyclohexanecarboxylic acid ethyl ester (trinexapac-ethyl).
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