Imazethapyr, glyphosate-isopropylamine salt, and glyphosate-sodium sesqui salt plus 2,4-D injured bahiagrass severely for 4 to 6 wk after treatment (WAT) but effectively controlled seedheads for 10 WAT without permanently reducing turf density. Imazethapyr applied twice at 0.08 kg ha-1 suppressed vegetative growth of mowed bahiagrass by 5 WAT while unmowed turf was suppressed 62% by 6 WAT. Glyphosate-isopropylamine salt suppressed vegetative growth by 3 WAT, but did not consistently suppress unmowed bahiagrass. Bahiagrass treated with glyphosate-sodium sesqui salt injured bahiagrass more than glyphosate-isopropylamine salt when each was applied at the same rate. CGA 163935 suppressed bahiagrass seedheads for 8 WAT and vegetative growth from 2 to 4 WAT. The activity of mefluidide, MON 4620 plus paclobutrazol, paclobutrazol plus mefluidide, and flurprimidol plus mefluidide was minimal on bahiagrass.

Mon 4620 at 2.8 kg ai/ha, paclobutrazol plus mefluidide at 1.1 plus 0.4 kg ai/ha, and flurprimidol plus mefluidide at 1.1 plus 0.4 kg ai/ha were applied on four dates to determine their influence on highly maintained tall fescue turf. Seedhead suppression was good to excellent by Mon 4620 applied March 1 or 18 and by paclobutrazol plus mefluidide and flurprimidol plus mefluidide applied anytime from March 1 until April 1. None of the plant growth regulators (PGRs) suppressed seedheads effectively when applied April 15 when the grass was near the end of the rapid growth cycle and just before seedhead emergence. Vegetative growth of mowed tall fescue was suppressed for 8 weeks in 1987 when PGRs were applied March 1 immediately after full green-up. Application dates were not as important in 1988 as in 1987. Tall fescue was injured the least by Mon 4620 applied in March and by flurprimidol plus mefluidide applied on March 18. Paclobutrazol plus mefluidide injured the turf severely regardless of application date.

CGA 163935, paclobutrazol, and paclobutrazol plus mefluidide were evaluated for their growth regulating effect on centipedegrass over 3 yr. Paclobutrazol did not effectively suppress seedhead production or vegetative growth. Paclobutrazol plus mefluidide at 1.1 + 0.3 kg ai ha–1 in each of two applications at a 2-wk interval suppressed seedhead development 77% (average of 3 yr) at 10 wk after the initial treatment without severe injury or loss of stand, but duration of vegetative growth suppression was variable (0 to 6 wk). CGA 163935 applied at 0.4 kg ai ha–1 and followed by 0.2 kg ai ha–1 2 wk later suppressed vegetative growth of mowed and nonmowed centipedegrass for 10 wk, while suppressing seedhead production for 3 to 5 wk. CGA 163935 caused severe injury and stand loss of centipedegrass.

Research was conducted in 1990 through 1992 to examine the vegetative and reproductive growth regulating activity of imazaquin and AC 263,222 on common bermudagrass. AC 263,222 at 0.06 kg ha−1, alone and in combination with imazaquin (0.21 kg ai ha−1), significantly reduced seedhead number, seedhead height, and vegetative canopy height for a 4-wk period after both May and July treatment. Imazaquin (0.42 kg ai ha−1) applied alone resulted in less turfgrass discoloration, but suppressed vegetative and reproductive growth of common bermudagrass less as compared with treatments containing AC 263,222.