Turf managers combine ethephon with trinexapac-ethyl (TE) on bentgrass greens to suppress annual bluegrass, inhibit turf growth, and enhance turf quality; however, effects of this growth regulator combination have not been reported on bermudagrass greens. Two experiments were conducted at the Clemson University Greenhouse Complex to investigate the response of ‘TifEagle’ bermudagrass to ethephon and TE. TifEagle bermudagrass plugs were placed in pots with 23-cm depths, 324-cm2 total surface areas, and a soil medium of an 85:15 (v/v) sand and peat moss mix. Ethephon was applied at 0, 3.8 (EP1), and 7.6 (EP2) kg ai/ha/3 wk with TE at 0 and 0.04 kg ai/ha/ 3 wk over a 9-wk period. Initial responses of bermudagrass to ethephon included chlorotic leaves and severe thinning. Bermudagrass treated with ethephon had quality reduced as much as 33% from nontreated turf. TE enhanced turf quality 4 to 22% from 4 to 9 wk after initial treatment. TE helped mask ethephon-induced quality decline after the third application. In the presence of TE, bermudagrass clipping yield was reduced from nontreated turf by 57, 70, and 72% when ethephon was applied at 0, 3.8, and 7.6 kg/ha/3 wk. Ethephon linearly reduced root mass after 9 wk from nontreated turf by 20 and 33% at 3.8 and 7.6 kg/ha/3 wk, respectively. Compared with respective ethephon rates alone, bermudagrass treated with TE and ethephon at 0, 3.8, and 7.6 kg/ha/3 wk, averaged 28, 8, and 15% more root mass. Ethephon at 3.8 and 7.6 kg/ha/3 wk without TE reduced TifEagle bermudagrass root length 14 and 16%, respectively, compared with untreated turf. Bermudagrass treated with ethephon at 0, 3.8, and 7.6 kg/ha/3 wk with TE averaged 3, 11, and 17% higher root length compared with respective ethephon rates after 9 wk. Overall, ethephon may have negative effects on TifEagle root mass, root length, and turf quality. However, combining ethephon with TE may help reduce these deleterious effects.
Nomenclature: Ethephon, (2-chloroethyl)phosphonic acid; trinexapac-ethyl, 4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester; annual bluegrass, Poa annua L.; TifEagle bermudagrass, Cynodon dactylon × C. transvaalensis.
Additional index words: Dwarf bermudagrass, plant growth regulator, turf injury.
Abbreviations: GA, gibberellic acid; PGR, plant growth regulator; TE, trinexapac-ethyl; WAIT, weeks after initial treatment.