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.

Common bermudagrass [Cynodon dactylon (L.) Pers. #3 CYNDA] and johnsongrass [Sorghum halepense (L.) Pers. # SORHA] ecotypes were collected from seven locations in Texas. Ecotype responses to glyphosate [N-(phosphonomethyl)glycine], SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate), sethoxydim {2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, fluazifop {(+)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, and quizalofop {(+)-2-[4-[(6-chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid} were evaluated in 1982, 1983, and 1984. Johnsongrass ecotype-by-herbicide interactions and ecotype differences were detected in only one of three years. Differences were observed consistently among the herbicide treatments. Numerous bermudagrass ecotype-by-herbicide interactions were detected each year with greater diversity occurring with less-than-optimum herbicide rates. The interactions were herbicide-by-ecotype specific and were not predictable with respect to geographic site of collection.

A study was conducted to evaluate effects of application timing and sulfometuron rate on weed control and bermudagrass tolerance. Sulfometuron was applied at rates from 13 to 105 g ai/ha and compared to 1120 g ae/ha 2,4-D amine. Control of Italian ryegrass and common vetch was not affected by October, November, December, or March application dates and 39 to 105 g/ha sulfometuron provided equivalent control of both species 6 mo after the initial treatment. Percent green cover of bermudagrass at 6 mo after the initial treatment was 22% or less following March applications compared to 36% or greater when applied in October, November, or December. More bermudagrass injury occurred following March treatments of 52 g/ha or greater sulfometuron where green cover was 14% and less compared to 22 and 30% green cover following 13 g/ha sulfometuron or 1120 g/ha 2,4-D amine, respectively.

Oxadiazon [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] applied to dormant bermudagrass [Cynodon dactylon (L.) Pers. ‘Tifway’ ♯ CYNDA] retarded early foliar growth more than other herbicides evaluated. When bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] treatments were delayed until after bermudagrass initiated spring growth, foliar growth and quality were generally lower than when the treatments were applied to dormant turf. Retardation of early foliar bermudagrass growth by 2,4-D [(2,4-dichlorophenoxy)acetic acid] + mecoprop {2-[(4-chloro-o-tolyl)oxy] propionic acid} + dicamba (3,6-dichloro-o-anisic acid) was generally the same whether applied to dormant or semidormant turf. This combination of herbicides reduced the quality and density of bermudagrass when applied to growing but not to dormant turf. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] did not retard bermudagrass growth or affect density whether applied to dormant or semidormant turf, but turf quality was slightly lower when atrazine was applied to semidormant turf.

In two separate field experiments conducted over time, at-planting preemergence (PRE) applications of sulfometuron at 110 to 150 g ai/ha followed by March applications of sulfometuron at 30 g/ha or metribuzin at 2,580 g ai/ha at the start of the initial (plant cane) growing season controlled more bermudagrass and johnsongrass emerging in sugarcane from rhizome and stolon pieces than standard at-planting followed by March applications of atrazine at 2,240 g ai/ha (no control), metribuzin at 2,580 g ai/ha, or pendimethalin at 2,240 g ai/ha. Treatments containing at-planting applications of imazapyr at 280 g ai/ha or thiazopyr at 560 g ai/ha did not provide levels of control similar to sulfometuron. Crop injury in excess of 10% occurred only when imazapyr at 280 g/ha (18 to 42%) or sulfometuron at 30 g/ha (11 to 32%) was applied in March to emerging sugarcane. Sugarcane stalk numbers, stalk heights, and ultimately cane and sugar yields were increased when compared to the standards with all sulfometuron treatments and when thiazopyr was applied at planting and again in March.

CGA 163935 was evaluated for its growth regulating effect on common bermudagrass for two years and ‘Tifway’ bermudagrass for four years. The vegetative growth of mowed common bermudagrass was suppressed for 5 wk when CGA 163935 was applied at 0.2 kg ha–1 followed by 0.1 kg ha–1 2 wk later and mowed Tifway bermudagrass was suppressed for 4 wk after application of 0.2 kg ha–1. CGA 163935 suppressed vegetative growth of non-mowed common bermudagrass for 9 wk and non-mowed Tifway bermudagrass for 2 to 8 wk at the same rates. Common bermudagrass tolerated CGA 163935 when applied initially at 0.2 kg ha–1 and followed by 0.1 kg ha–1 at a 2-wk interval for a total 0.3 kg ha–1 rate. However, common bermudagrass was severely injured (> 30%) when CGA 163935 was applied at 0.2 kg ha–1 in each of two applications for a total rate of 0.4 kg ha–1. Tifway bermudagrass tolerated CGA 163935 when applied at 0.2 kg ha–1 as a single application or when the 0.2 kg ha–1 was followed by 0.1 kg ha–1 at a 4-wk interval. Tifway bermudagrass was severely injured (> 30%) when CGA 163935 was applied at 0.4 kg ha–1 as a single application or when 0.2 kg ha–1 was followed by 0.1 kg ha–1 at 2- or 3-wk interval. Seedheads were suppressed in common bermudagrass for 1 to 2 wk with CGA 163935 at 0.4 kg ha–1.

Field experiments conducted from 1990 through 1993 evaluated single and sequential applications of various postemergence graminicides for common bermudagrass control in peanut. UBI-1956 at 70 and 100 g/ha applied early POST (EP) or sequentially, controlled common bermudagrass equivalent to fluazifop-P applied EP or sequentially. Clethodim provided variable common bermudagrass control. Clethodim applied EP provided better control than sethoxydim while control from sequential clethodim applications were equivalent to fluazifop-P. Fenoxaprop-ethyl alone failed to control common bermudagrass while the addition of fluazifop-P to fenoxaprop-ethyl improved control at least 22% in two of three years. Quizalofop applied EP and fenoxaprop applied sequentially provided common bermudagrass control equivalent to fluazifop-P. Fenoxaprop-ethyl or sethoxydim applied once or twice controlled common bermudagrass similarly. Peanut yield increases from common bermudagrass control were erratic.

The influence of green kyllinga and white kyllinga on common bermudagrass growth was compared by planting one to three green or white kyllinga rhizomes with two bermudagrass stolons. White kyllinga reduced bermudagrass shoot fresh weight to 56% of the control, but green kyllinga did not reduce bermudagrass shoot fresh weight significantly. Increased planting densities of both kyllinga species linearly increased kyllinga shoot fresh weight and decreased bermudagrass shoot fresh weight similarly. White kyllinga produced more leaf fresh weight, leaf area, and roots and rhizomes than green kyllinga, which produced more shoots and inflorescences.

Control of natural infestations of dogfennel [Eupatorium capillifolium (Lam.) Small # EUPCP] and woolly croton (Croton capitatus Michx. # CYNCP) in a bermudagrass [Cynodon dactylon (L.) Pers. # CYNDA] – dallisgrass (Paspalum dilitatum Poir. # PASDI) sward ranged from 20 to 100% with surface-applied tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N-dimethylurea}. In general, efficacy increased with rate of application from 0.6 to 1.1 kg ai/ha, and with time to 107 days after treatment. Only 0.6 kg ai/ha controlled less than 90% of the weeds during the growing season. Dry matter yields of desirable forage ranged from 60 to 290 kg/ha more with tebuthiuron treatment than in the untreated check. There were no consistent differences in forage quality among treatments, which indicates that tebuthiuron had no detrimental effects upon the bermudagrass or dallisgrass.

Dithiopyr and prodiamine are new preemergence herbicides for crabgrass control in tall fescue and bermudagrass turf. A field experiment was conducted over a 2-yr period to determine the lowest rates of dithiopyr and prodiamine needed to control large crabgrass effectively in tall fescue and common bermudagrass. Prodiamine applied at 0.17 kg ai/ha in each of two applications controlled 92 to 93% of large crabgrass by late August in common bermudagrass and 78 to 85% in tall fescue. Dithiopyr applied at 0.11 kg ai/ha in each of two applications controlled 85 to 89% of large crabgrass in common bermudagrass, but the control was not consistent across years at any rate in tall fescue. Dithiopyr applied at 0.56 kg/ha on tall fescue controlled 91% of large crabgrass in 1993, but only 38% in 1994. The higher control with dithiopyr in common bermudagrass was due to greater competition with germinating large crabgrass seeds and emerging seedlings during the summer, compared with little or no competition from tall fescue. The quality of tall fescue and common bermudagrass treated with dithiopyr and prodiamine was generally higher in plots where large crabgrass was effectively controlled than in plots with poor control. In general, dithiopyr did not control large crabgrass as effectively in tall fescue as in common bermudagrass, while the control with prodiamine was similar for the two turfgrass species.

Plant growth regulators were evaluated on common and African ‘Tifway’ bermudagrass. Flurprimidol plus mefluidide applied at 1.1 plus 0.14 kg ha-1 and followed by 0.56 plus 0.14 kg ha-1 at 2- to 3-week interval suppressed vegetative growth of mowed common bermudagrass for 5 wk (17 to 23%) and unmowed turf for 6 wk (40%), but severely injured the turf. The injury ranged from 25 to 32% from 2 to 6 wk after treatment. The plant growth regulators that injured common bermudagrass less than flurprimidol plus mefluidide did not suppress the mowed turf for as long a period. Vegetative growth of common bermudagrass not mowed was suppressed for 6 wk when treated once with flurprimidol plus mefluidide and twice with flurprimidol, mefluidide, imazethapyr, paclobutrazol (1.1 plus 1.1 kg ha-1), and paclobutrazol plus mefluidide. Of the plant growth regulators evaluated, only imazethapyr suppressed common bermudagrass seedheads. The suppression was 70% for 4 wk, but reduced to <70% by 5 wk. Paclobutrazol applied initially at 1.1 kg ha-1 and followed at 0.56 kg ha-1 suppressed vegetative growth of mowed Tifway bermudagrass for 5 wk and unmowed turf for 8 wk without causing severe injury. The suppression of mowed Tifway bermudagrass with two applications of paclobutrazol was as good or better than with any other plant growth regulator. All plant growth regulators suppressed vegetative growth of unmowed Tifway bermudagrass for 8 wk.

The behavior of the methyl ester of 14C-haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} in common bermudagrass [Cynodon dactylon (L.) Pers. # CYNDA] stolons was examined in greenhouse experiments at two different seasons. The 14C from the herbicide applied on the leaves of a stolon node translocated no more than 3% of the applied radioactivity to the apex and base. Movement out of stolons was not significant. In early summer less than 1% translocated in each direction; in early fall more than 2% moved to the apex and less than 1% toward the base. Decrease of 14C recovery with time was evident in both seasons, particularly in early summer. Haloxyfop volatilization from the leaf surface apparently plays a significant role in recovery decrease. The 14C found in stolons in early summer was approximately the same as that of early fall, although herbicide remaining available for uptake on the leaf surface was lower in the former season. We suggest that environmental conditions that favor volatilization could enhance uptake.

Field experiments were established in 1989 and 1990 at the Southern Piedmont Conservation Research Center near Watkinsville, GA, to determine effects of coastal bermudagrass density on cotton in a conservation tillage system. Cotton height, canopy width, leaf area indices, and seed cotton yields were determined at coastal bermudagrass densities of 0 to 3600 kg ha−1 as achieved by herbicide inputs. Soil water measurements were recorded in cotton plots with a range of coastal bermudagrass densities using time domain reflectometry. Cotton growth and yields were reduced by coastal bermudagrass competition both years of the study. At the highest coastal bermudagrass density of 3600 kg ha−1, cotton height was reduced compared to cotton alone as early as 5 wk after planting. Seed cotton yields were reduced 25% at the highest coastal bermudagrass densities both years of the study. At the 15-cm soil depth, coastal bermudagrass significantly reduced soil water in cotton. Soil water in cotton at 30, 45, and 60 cm was not affected by coastal bermudagrass.

Field experiments were conducted to determine effects of adding 2.8 kg/ha (NH4)2SO4 and/or substituting BCH 81508 S for crop oil with sethoxydim applied to large crabgrass, corn, johnsongrass, and common bermudagrass. Adding (NH4)2SO4 did not affect control of johnsongrass or common bermudagrass but did increase control of large crabgrass and corn by 6 and 15%, respectively. Cora control was enhanced more by (NH4)2SO4 at lower sethoxydim rates. Substituting BCH 81508 S for crop oil increased seedling johnsongrass, large crabgrass, common bermudagrass, rhizome johnsongrass, and corn control by 7, 9, 9, 10, and 15%, respectively. A sethoxydim rate by spray adjuvant interaction was observed with seedling johnsongrass, common bermudagrass, and corn where response to BCH 81508 S decreased as sethoxydim rates increased. The effects of substituting BCH 81508 S for crop oil and adding (NH4)2SO4 were independent.

An undesirable bermudagrass [Cynodon dacytlon (L.) Pers. # CYNDA] often must be removed before converting to an improved bermudagrass turf or to a different turfgrass species. Because bermudagrass control with glyphosate [N-(phosphonomethyl)glycine] has been inconsistent, an experiment was initiated to determine the necessary application rates and frequency for glyphosate and SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) to control bermudagrass. Both glyphosate and SC-0224 applied in three applications (May, June, and August) had controlled three bermudagrass hybrids [Cynodon transvaalensis Burtt-Davy # CYNTR x C. dactylon (L.) Pers. Tifway’, Tifgreen’, and ‘Tifdwarf’] and ‘Ormond’ bermudagrasses when evaluated the next June. None of the cultivars were controlled effectively with either herbicide applied in one (May) or two (May and June) applications regardless of rate. Control with glyphosate and SC-0224 was similar.

Preemergence (PRE) and postemergence (POST) herbicides were sequentially applied to common bermudagrass over a two-year period to determine the lowest herbicide rates required to maintain acceptable large crabgrass and goosegrass control. Large crabgrass control was consistently higher in late August when MSMA at 2.2 kg ha−1 was applied to plots previously treated with dithiopyr at 0.3 kg ha−1 (99%) in 1991, and either pendimethalin at 1.1 kg ha−1 (95%) or oxadiazon at 1.1 kg ha−1 (94%) in 1992 than when either herbicide was applied alone (≤ 79%). Goosegrass control was also higher in late August when MSMA plus metribuzin at 2.0 + 0.14 kg ha−1 was applied to plots treated with pendimethalin at 1.7 kg ha−1 (71%) in 1991, with oxadiazon at ≤ 2.2 kg ha−1 (≤ 89%) in 1992, and with dithiopyr at 0.4 kg ha−1 (≤ 96%) both years than when the herbicides were applied alone. Diclofop at 1.1 kg ha−1 applied alone as POST controlled ≥ 96% goosegrass throughout the two-year period.

Experiments were conducted over a 3-yr period to determine the rate and frequency of herbicide application needed to control common bermudagrass growing in a tall fescue turf. In Experiment I, fenoxaprop plus ethofumesate applied at 0.2 + 1.7 kg/ha in late April and repeated at the same rate at 3- to 4-wk intervals for a total of five applications resulted in excellent (≥ 97%) common bermudagrass suppression. The suppression was higher from combination of fenoxaprop and ethofumesate than when fenoxaprop was applied at 0.2 kg/ha in five applications (≤ 67%). In Experiment II, fenoxaprop plus ethofumesate applied at 0.2 +1.7 kg/ha required four applications per year to effectively suppress common bermudagrass (95%) in 1993, but five applications were needed to obtain similar suppression (96%) in 1994. Tifway bermudagrass was not suppressed during 1994 when fenoxaprop plus ethofumesate were applied at 0.2 +1.7 kg/ha in each of five applications (30%). In most instances, fenoxaprop plus ethofumesate applied at 0.2 +1.7 kg/ha caused only slight to moderate (< 30%) injury to tall fescue for 1 to 2 wk after treatment. When injury occurred, it was temporary as the turf fully recovered within 2 to 3 wk after treatment. An exception occurred in early July 1992 when fenoxaprop plus ethofumesate caused 44% injury to tall fescue after the four applications.

Field experiments were conducted in 1982 through 1986 to evaluate the effect of six postemergence grass herbicides, clethodim, the methyl ester of diclofop, the butyl ester of fluazifop-P, the methyl ester of haloxyfop, the methyl ester of quizalofop, and sethoxydim, on 31 seedling grass species. All herbicides except diclofop controlled most of the species tested. None of the herbicides controlled rattail fescue or red fescue. Only clethodim and haloxyfop controlled annual bluegrass.

Bermudagrass growing in a creeping bentgrass green is a severe problem where both grasses are grown. An experiment was conducted to determine the effects of multiple flurprimidol-herbicide applications on tolerance of bentgrass and on suppression of three bermudagrass cultivars in bentgrass. Application of 1.4 kg ai ha–1 flurprimidol on April 15 and 0.8 kg ha–1 repeated on June 1 injured creeping bentgrass 44% in 1988 and 22% in 1989. Bermudagrass was suppressed from the two flurprimidol applications until mid-June in 1988. Growth in 1989 was not influenced by number of applications since bermudagrass was suppressed only until late May. Application of 0.8 + 54 kg ai ha–1 flurprimidol plus siduron on April 15 and 0.4 + 27 kg ha–1 on June 1 injured creeping bentgrass 23 to 28% and suppressed bermudagrass until mid-July in 1988 and mid-June in 1989. Application of 0.8 + 1.7 kg ha–1 flurprimidol plus ethofumesate on April 15 and 0.4 + 0.8 kg ha–1 on June 1 injured creeping bentgrass 25 to 28% and effectively suppressed bermudagrass until late August in 1988 and late June in 1989. Application of 0.8 + 54 kg ha–1 flurprimidol plus siduron or 0.8 + 1.7 kg ha–1 flurprimidol plus ethofumesate applied in June or June and July to plots treated in April did not improve bermudagrass suppression. In most instances there was an inverse relationship between bermudagrass suppression and number of bermudagrass stolons. There were interactions between flurprimidol-herbicide treatments on bermudagrass cultivars on number of stolons but not on suppression.

The objective of this study was to determine how selected herbicides affect sod tensile strength and rooting of mature and immature turfs of ‘Tifway’ bermudagrass. Both immature and mature turf had 100% ground cover, but only mature turf had tensile strength adequate for harvesting and handling. Sod tensile strength at 2, 4, and 8 weeks after application generally was unaffected by herbicide treatment, although imazapyr killed bermudagrass top growth. Root number and root length initially were depressed by imazapyr, bensulide, napropamide, sethoxydim, and sulfometuron at most rates and intervals tested. Eight weeks after treatment, root length, root number, and sod tensile strength for all treatments, except those with imazapyr, were similar to that of the untreated control.