Eleven herbicides applied in May, were evaluated for yankeeweed control in East-Central Texas. Yankeeweed cover 1 yr later was reduced to 5% or less by 0.28 kg ha-1 of picloram; 0.56 kg ha-1 of clopyralid, glyphosate, or dicamba; 0.28 + 0.84 kg ha-1 of dicamba + 2,4-D, and 1.1 kg ha-1 triclopyr compared with 30% cover in the untreated area. Chlorsulfuron and metsulfuron at 0.07 kg ha-1 reduced yankeeweed cover to 12 and 7%, respectively. Dalapon, 2,4-D, and tebuthiuron were relatively ineffective. Most herbicides, reduced woolly croton cover within 1 mo after treatment compared to the untreated areas, but 2,4-D at 0.28 kg ha-1 and chlorsulfuron at 0.02 kg ha-1 and 0.07 kg ha-1 were most effective after 4 mo. All herbicides, except dalapon at 1.1 kg ha-1 or less and most rates of 2,4-D and tebuthiuron, reduced partridgepea cover during the year of application. Total grass cover was increased 4 and 12 mo following treatment with clopyralid, picloram, dicamba, and triclopyr. On separate sites, bahiagrass and coastal bermudagrass accounted for most of the increased grass cover.

A 3-yr study investigated highbush blackberry control in bahiagrass turf using selective herbicides. Triclopyr applied alone at ≤ 0.56 kg/ha and in combination with other herbicides provided best (75 to 95%) control for up to 52 wk after treatment with minimal damage to bahiagrass turf. Triclopyr formulations (3A vs 4EC) provided similar highbush blackberry control and bahiagrass tolerance. The addition of either 2,4-D, dicamba, hexazinone, or sulfometuron to triclopyr provided slightly better blackberry control, but increased bahiagrass turf damage. Fluroxypyr applied at 0.14 to 0.28 kg/ha provided 60 to 80% control of highbush blackberry 12 WAT. Glyphosate and glufosinate treatments provided unacceptable highbush blackberry control and/or unacceptable bahiagrass turf injury. The addition of oxadiazon for residual control of subsequent highbush blackberry emergence was ineffective.

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.

Field studies were conducted at Charleston, SC to evaluate the effects of six chemical treatments on bahiagrass and the potential of these treatments to reduce mowing operations. Sulfometuron, maleic hydrazide, and imazethapyr plus imazapyr, in decreasing order of effectiveness, were the most consistent treatments evaluated during the 2-yr study. Sulfometuron reduced bahiagrass vegetative height (23%) for 6 to 8 WAT and suppressed 87 to 92% of seedheads without adversely affecting turf quality. All treatments temporarily discolored turf; however, effects were not objectionable for medium- to low-quality turf settings. Sulfometuron, maleic hydrazide, and imazethapyr plus imazapyr controlled growth and maintained acceptable turf quality for an average of 9, 9, and 8 wk, respectively; thereby reducing mowing operations by an average 29%. Mefluidide plus fluazifop-P, mefluidide plus sulfometuron, and chlorosulfuron were the least effective and/or consistent treatments evaluated.

Growth-regulating characteristics of trinexapac-ethyl, paclobutrazol, and flurprimidol were investigated on ‘Tifway’ bermudagrass and four turfgrass weeds (large crabgrass, goosegrass, bahiagrass, and purple nutsedge). All treatments reduced the height of Tifway bermudagrass (25 to 37%) and large crabgrass (14 to 34%), but the height of purple nutsedge, goosegrass, and bahiagrass was not consistently changed. In 1995, all rates of trinexapac-ethyl reduced clipping weights of Tifway bermudagrass (70 to 87%) and bahiagrass (53 to 59%) more than large crabgrass, goosegrass, or purple nutsedge (< 39%). Trinexapac-ethyl (0.4 kg ai/ha) and paclobutrazol (1.1 kg ai/ha) applications increased both large crabgrass clipping weight and canopy visible density. Increased large crabgrass density was attributed to greater tiller numbers with trinexapac-ethyl (60 tillers/pot) and paclobutrazol (63 tillers/pot) compared to untreated large crabgrass plants (53 tillers/pot). Weed growth was not suppressed as much as Tifway bermudagrass growth; therefore, turfgrass stands may be adversely affected by plant growth regulator use under weedy conditions.

Field studies were conducted in 1993–1994 and 1994–1995 to evaluate the effects of preherbicide mowing and herbicide rate on tropical soda apple (TSA) control. Mature TSA plants were mowed one, two, or three times to a 7.5-cm stubble with a 60-d interval between mowings. Triclopyr was applied at 0, 0.6, and 1.1 kg ai/ha at 375 L/ha at 207 kPa 60 d after each mowing treatment. Mowing TSA plants twice before an application of 0.6 kg ai/ha triclopyr resulted in 100% control. Tropical soda apple control (2-yr average) for the triclopyr treatment increased between one (28% control) and two (82% control) preherbicide mowings, with no additional control benefits from three mowings (84% control). In a second study, TSA control increased from 10% 60 d after a single mowing to 92% after three consecutive mowings at 60-d intervals with no herbicide. Total nonstructural carbohydrates in TSA crowns decreased from 19.1% for unclipped plants to 4.3% 60 d after three preherbicide mowings.

Hexazinone (1.12 kg ai/ha), triclopyr (1.12 kg ai/ha), metsulfuron (0.008 kg ai/ha), dichlorprop + 2,4-D, glyphosate (2.8%), and triclopyr (2%) + diesel oil (98%), applied as a broadcast or spot (individual plant) treatment, were evaluated over two years in south Florida for tropical soda apple (TSA) control and their effects on grass ground cover. For broadcast treatments, triclopyr (98%) and hexazinone (93%), had significantly (P < 0.05) higher percent control of marked TSA plants 90 d after herbicide application. However, triclopyr (99%) had significantly higher grass ground cover than hexazinone (78%). Hexazinone severely damaged Pangola digitgrass, but had no effect on bahiagrass. For spot treatments, dichlorprop + 2,4-D (100%) had the highest percent total control of TSA and least effect on grass ground cover (96%) 90 d after herbicide application, followed by glyphosate (96% control) and triclopyr + diesel oil (95% control). Based on acceptable (>90%) TSA control and grass ground cover, triclopyr broadcast or dichlorprop + 2,4-D spot provided the greatest control. With either application method, repeated herbicide applications will be necessary to eliminate TSA because of rapid seedling emergence following control of existing plants.

Sulfometuron, when applied as a foliar and/or soil application, prevented regrowth of bahiagrass. Sulfometuron application did not reduce regrowth of centipedegrass regardless of method of application. Sulfometuron was absorbed by the roots and foliage of centipedegrass and bahiagrass. Symplasmic translocation of the herbicide was evident in both species. Translocation of foliar-applied sulfometuron increased from approximately 1% at 48 h after application to 23% at 72 h in bahiagrass. Metabolism of sulfometuron was greater in centipedegrass (69% of foliar-applied, 10% of root-applied) at 72 h after application than in bahiagrass (30% of foliar-applied and 4% of root-applied). Tolerance of centipedegrass to sulfometuron appeared to be related to a high degree of herbicide metabolism in this species.