Smutgrass [Sporobolus poiretii (R. & S.) Hitchc.] in native grass and ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] pastures near Caldwell, Texas, was sprayed with herbicides in 1975 and 1976. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] at 4.5 kg/ha; dalapon (2,2-dichloropropionic acid) at 5.6 kg/ha; glyphosate [N-(phosphonomethyl)glycine] at 0.6 and 2.2 kg/ha; and bromacil (5-bromo-3-sec-butyl-6-methyluracil), tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] at 1.1 and 2.2 kg/ha reduced smutgrass foliar cover, particularly if applied from July to November. Dalapon, tebuthiuron, and hexazinone were the most effective herbicides for reducing smutgrass foliar cover. Other grasses generally replaced smutgrass controlled with hexazinone or tebuthiuron, while broadleaf species mostly replaced smutgrass in plots controlled with dalapon or glyphosate. Dalapon, glyphosate, bromacil, hexazinone, and tebuthiuron caused some injury to Coastal bermudagrass for 3 or 4 months following treatment. By fall of the year after treatment Coastal bermudagrass cover in treated plots was equal to or greater than that in untreated plots.

Between 1982 and 1986, spring treatments of haloxyfop, fluazifop, and sethoxydim all applied at 400 g ai/ha alone and combined with dalapon at 3400 g ai/ha were evaluated for quackgrass control and subsequent effect on established birdsfoot trefoil seed production. Haloxyfop alone and combined with dalapon were superior to fluazifop or sethoxydim alone or mixed with dalapon for controlling quackgrass and other grass weeds. Birdsfoot trefoil seed yield averages over 3 yr were 310, 160, 150, and 180 kg/ha after treatment with haloxyfop, fluazifop, sethoxydim, and dalapon, respectively, compared to a control yield of 80 kg/ha. Yields were lower, 220 kg/ha, with combinations involving haloxyfop plus dalapon compared to haloxyfop alone.

Twenty herbicides were applied to a rangeland pasture in the Post Oak Savannah Resource Area of Texas in April 1978 and May 1979. At time of treatment, total vegetation cover was 88 to 100%, with 36% grasses and 52 to 64% broadleaf cover. From May 31 through September, total, grass, and broadleaf covers were 89 to 100, 51 to 65, and 27 to 44%, respectively. One to 2 months after treatment, grass cover generally increased except where certain herbicides, particularly bromacil (5-bromo-3-sec-butyl-6-methyluracil), dalapon (2,2-dichloropropionic acid), glyphosate [N-(phosphonomethyl)glycine], or hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4 (1H, 3H)-dione] had been applied. By September or October in the year of application only dalapon consistently reduced grass cover. In the year following treatment, grass cover was still reduced on the dalapon-treated plots. Most herbicides reduced broadleaf cover in the year of treatment. Broadleaf cover returned most rapidly to those areas treated with dalapon. During the year following treatment, broadleaf cover remained low on plots treated with picloram (4-amino-3,5,6-trichloropicolinic acid), 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and picloram + 2,4,5-T. For plots treated in 1978, the grass and broadleaf standing-crop weights of untreated plots were 490 and 450 kg/ha, respectively, in October 1978, and 2707 and 1033 kg/ha in October 1979. In 1978, grass weight increased with several herbicide treatments whereas only dalapon increased the broadleaf weight. For plots treated in May 1979 and harvested in September 1979, grass and broadleaf standing-crop weights of untreated plots were 2629 and 607 kg/ha, respectively.

The influence of herbicide formulation and time of herbicide application on smutgrass [Sporobolus poiretii (Roem. & Schult.) Hitchc.] control and phytotoxicity to the major perennial forage-grass species were determined. Dalapon (2,2-dichloropropionic acid) applied at rates of 4.8 kg/ha and higher gave excellent control regardless of time of application. However, 4.8 kg/ha dalapon applied to Pensacola bahiagrass (Paspalum notátum Flügg ‘Pensacola′) and bermudagrass [Cynodon dactylon (L.) Pers.] in the spring, and to tall fescue (Festuca arundinacea Schreb. ‘Ky 31′) in the fall and spring, was phytotoxic. Applications of tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} 80W (80% wettable powder) formulation at 2.4 kg/ha, or fertilizer coated with tebuthiuron at 2.4 kg/ha, gave excellent smutgrass control. The pelleted formulation of tebuthiuron was less phytotoxic to the forage species than the other formulations.

The herbicides 2,4-D [(2,4-dichlorophenoxy) acetic acid], dalapon (2,2-dichloropropionic acid), glyphosate [(N-phosphonomethyl)glycine], paraquat (1,1’-dimethyl-4,4’-bypiridinium ion), and pronamide [3,5-dichloro-(N-1,1-dimethyl-2-propynyl)benzamide] were applied at selected rates and dates to quackgrass [Agropyron repens (L.) Beauv. ♯ AGRRE]-infested alfalfa (Medicago sativa L.) sod in 1979 and 1980 to suppress vegetation for subsequent establishment of alfalfa without tillage. The influence of herbicides on weed control, alfalfa seedling density and visual stand, and forage yield and quality was assessed for 3 yr. During establishment, all herbicides except 2,4-D effectively controlled quackgrass. Glyphosate applied broadcast increasingly suppressed the existing sod as the rate was increased from 0.6 to 1.6 kg ai/ha. The effectiveness of herbicides as measured by total (old and new) plant density was closely related to the suppression of the sward. While the substitution of new alfalfa plants for old ones was not necessary under dense (40 plants/m2) alfalfa stands, completely controlling the vegetation with glyphosate resulted in sustained productivity throughout the experimental period. After 3 yr, alfalfa percentage and yield were highest when glyphosate was broadcast at 1.6 kg/ha. Improvement in forage quality, as estimated by the concentrations of crude protein and neutral-detergent fiber, was closely related to grass control.

Dalapon (2,2-dichloropropionic acid), tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] were evaluated for smutgrass [Sporobolus poiretii (R.&S.) Hitchc] control in bahiagrass (Paspalum notatum Flugge.) pastures. Dalapon and hexazinone provided the best smutgrass control but injured the bahiagrass. Forage treated with hexazinone at 1.7 kg/ha or less recovered within 6 months; however, the effects of the initial injury from dalapon at 2.2 kg/ha could be detected for as long as 2 yr after treatment. Dogfennel [Eupatorium capillifolium (Lam.) Small] and broomsedge (Andropogon virginicus L.) replaced smutgrass and bahiagrass removed by dalapon. Higher rates of tebuthiuron than hexazinone (3.4 vs. 1.1 kg/ha) were required to control smutgrass adequately.

Field studies were conducted in 1984 and 1986 to identify herbicides that would control woolly croton and bitter sneezeweed on grazing land in the Blackland prairies of Texas. Herbicides included chlorsulfuron, clopyralid, dalapon, dicamba, 2,4-D, glyphosate, metsulfuron, picloram, tebuthiuron, 2,4,5-T, and triclopyr. Chlorsulfuron and metsulfuron applied at 0.018 kg ha-1 and 2,4-D, picloram, 2,4,5-T, and triclopyr at 0.28 kg ha-1 controlled >80% of the woolly croton. Metsulfuron controlled more than 90% of the bitter sneezeweed at 0.018 kg ha-1. Similar control was obtained with clopyralid, glyphosate, and picloram each at 0.28 kg ha-1. Bermudagrass cover increased with all herbicide treatments except dalapon at one of three sites.

A field study was conducted to develop systems using cultural and chemical methods for control of bermudagrass (Cynodon dactylon L.) in cotton (Gossypium hirsutum L.). Several control options were promising. On areas prepared either with a moldboard plow or a disk, the sodium and magnesium salts of dalapon (2,2-dichloropropionic acid) at 4.7 kg/ha directed to 25-cm-high cotton and repeated at the 40-cm height or the ethyl ester of difenopenten {4-[4-[4-(trifluoromethyl)phenoxy] phenoxy]-2-pentenoic acid} directed to 15-cm-high cotton and repeated at the 30-cm height, with either standard or close cultivation as needed, provided good bermudagrass control. On areas prepared with a moldboard plow, the isopropyl amine salt of glyphosate [N-(phosphonomethyl)glycine] at 4.4 kg/ha over-the-top as a fall application with cultivation as needed was promising.

Dalapon (2,2-dichloropropionic acid), TCA ester [ethyleneglycol bis(trichloroacetate)], MSMA (monosodium methanearsonate), and glyphosate [N-(phosphonomethyl)glycine] were evaluated for their effectiveness as spot spray treatments to johnsongrass [Sorghum halepense (L.) Pers.] 30, 75, or 100 cm tall from rhizomes. Glyphosate was also applied as a spot spray to soybeans [Glycine max (L.) Merr. ‘Pickett 71′] to determine its effect on stand losses and subsequent soybean yields. Glyphosate at a concentration of 6 or 12 g/L of water was the most effective treatment regardless of johnsongrass height. A single application provided excellent-to-complete seasonal control within 2 weeks after application. Repeated applications of dalapon, MSMA, and TCA ester would be needed for season-long control. Glyphosate at a concentration of 6 g/L of water applied to 0.5 m long spots of soybeans in late August reduced soybean yields 9, 17, and 28% while the stand was reduced 5,10, and 20%, respectively.

Various chemical and cultural treatments were evaluated for smutgrass [Sporobolus poiretii (R.&S.) Hitchc], control and their effects on pangolagrass (Digitaria decumbens Stent.) and bahiagrass (Paspalum notatum Flügge). Herbicide treatments were dalapon (2,2-dichloropropionic acid) at 1.7, 3.3, and 5.0 kg/ha with Sunoco HE spraying oil at 0, 9.4, 19.0 and 37.0 L/ha. Five weeks after herbicide treatment plots were clipped (clipped vs. nonclipped) and fertilized (0 vs. 112 kg/ha N). Increasing dalapon from 1.7 to 5.0 kg/ha increased smutgrass control and decreased the number of smutgrass plants/plot. Pangolagrass ground cover generally increased with fertilization, as the rate of dalapon increased up to 3.9 kg/ha. Bahiagrass ground cover decreased with rates of dalapon above 1.7 kg/ha. Increasing the rate of oil increased bahiagrass ground cover after 90 days. Nitrogen applied 5 weeks after dalapon treatment and semi-annually for 5 yr generally decreased ground cover of smutgrass and bahiagrass, but increased pangolagrass. Clipping treated smutgrass plants increased pangolagrass and bahiagrass ground cover while decreasing the ground cover of smutgrass.

Loss in activity of foliar-applied methyl ester of diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} occurred under low soil moisture conditions. A loss in control of yellow foxtail [Setaria lutescens (Weigel) Hubb.], wild oats (Avena fatua L.), little-seed canarygrass (Phalaris minor Retz.), and barnyardgrass [Echinochloa crus-galli (L.) Beauv.], was observed under greenhouse and growth chamber conditions. When soil was maintained at 2 to 3% above wilting point as compared to near field capacity, herbicide activity was decreased by 15 to 50%. High soil moisture (at or above 67% of field capacity) for at least 2 to 4 days following treatment was needed to achieve maximum effectiveness of the herbicide. Daily furrow irrigations for a period of 10 days following treatment of barnyardgrass in the field resulted in highest activity as compared to that under single irrigation regimes within the 10-day period. The effect of low soil moisture was minimized by increased rates of herbicide application. Hoe-29152 {methyl-2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoate} showed similar losses in activity associated with low soil moisture. No consistent changes in uptake or translocation of 14C-labeled diclofop could be detected in association with altered soil moisture status.

A continuous-belt herbicide wiper was developed to apply herbicides to weeds that are taller than cranberry (Vaccinium macrocarpon Ait.) plants. An endless belt with a sponge attached to the entire length of the belt moves through a reservoir containing a herbicide solution. A variable pressure wheel squeezes the excess liquid out of the sponge and returns it to the reservoir. The herbicide is deposited on the leaves of the weeds as the belt moves in a horizontal plane, perpendicular to the forward movement of the wiper. Control of Walter's sedge (Carex walteriana Bailey), woolgrass [Scirpus cyperinus (L.) Kunth] and switchgrass (Panicum virgatum L.) was obtained when glyphosate [N-(phosphonomethyl)glycine], dalapon (2,2-dichloropropionic acid), and paraquat (1, 1′-dimethyl-4,4′-bipyridinium ion) were applied using the continuous-belt wiper. No injury to cranberry plants was observed.

Field experiments were conducted in 1982 and 1983 at Stoneville, MS, to determine the susceptibility of 17 biotypes of bermudagrass [Cynodon dactylon (L.) Pers. ♯ CYNDA] to seven postemergence herbicides. Control, averaged over all biotypes 13 weeks after treatment, varied from 96% using haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid} at 0.56 kg/ha to 16% using fenoxaprop {(±)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid} at 0.28 kg/ha. Control among biotypes ranged from 89 to 96% using haloxyfop at 0.56 kg/ha and from 4 to 89% using dalapon (2,2-dichloropropanoic acid) at 11.2 kg/ha.

Glyphosate [N-(phosphonomethyl)glycine], dalapon (2,2-dichloropropionic acid), or paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) applied for edging control of bermudagrass [Cynodon dactylon (L.) Pers. ‘common ‘ # CYNDA] did not injure any of the eight woody ornamental species included in a 3-yr study. Paraquat applied in seven applications per year did not effectively control bermudagrass. Bermudagrass control was variable with glyphosate and dalapon during spring and summer; but repeated treatments at approximately 4-week intervals maintained effective control. In most instances, bermudagrass control was higher with glyphosate than with dalapon during September and October.

Seven herbicides and two herbicide combinations were applied once either preplant or postplant to control perennial grasses and forbs as planting-site preparation for 2-yr-old seedlings of ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and Douglas fir [Pseudotsuga menziesii var. glauca (Beissn.) Franco] at locations in Washington and Oregon. Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H, 3H)-dione] applied at 2.2 kg/ha provided most effective and lasting herbaceous weed control in both states. A combination of dalapon (2,2-dichloropropionic acid) and atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] applied at 9.0 + 4.5 kg/ha also proved similarly effective. In Washington, each conifer species responded with exponential growth increases over a 6-yr period. For ponderosa pine and Douglas fir, respectively, hexazinone treatment increased tree height by 58 and 70%, stem diameter by 70 and 69%, and stem-volume yield by 387 and 650% as compared to untreated checks. Corresponding gains for the two conifers associated with dalapon + atrazine were 73 and 54% in height, 63 and 46% in diameter, and 421 and 349% in yield.

Red clover (Trifolium pratense L.) was direct seeded into a grass sod after spraying with dalapon (2,2-dichloropropanoic acid), glyphosate [N-(phosphonomethyl) glycine], or paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) at rates of 5.6, 2.2, and 0.6 kg ai/ha respectively. Dalapon applied a few days prior to planting did not improve red clover stands in comparison to seeding in unsprayed sod. Applying glyphosate a few days prior to seeding in spring and summer invariably increased red clover stands, but paraquat was effective in only one of four spring or summer applications. Glyphosate applied the fall preceding a spring or summer seeding produced red clover stands superior to those after all spring treatments. Where glyphosate or paraquat was applied, water content of the upper 20 cm of the soil profile was greater during the first 10 days after treatment, relative to unsprayed plots or those treated with dalapon. By 30 days after application, the glyphosate-treated sods used less soil water than those treated with paraquat. Applications of glyphosate and paraquat greatly suppressed water utilization by oats (Avena sativa L.) in the greenhouse, based on water potential of the potting soil. Dalapon had little effect on water use by oat seedlings in the greenhouse.

Autumn desiccation of warm-season perennial grasses is one method to enhance the establishment and early production of overseeded cool-season annuals. Potential herbicides were compared with paraquat, glyphosate, and dalapon to desiccate a dallisgrass–bermudagrass sod for overseeding annual ryegrass over a 2-yr period. Fluazifop-P at ≥ 0.14 kg/ha, glufosinate at ≥ 1.12 kg/ha, and haloxyfop at ≥ 0.07 kg/ha provided good dallisgrass desiccation and ryegrass yields similar to those with dalapon and glyphosate. Dallisgrass recovery was inversely related to desiccation rating for all treatments except for paraquat. None of the herbicide treatments had the desired combination of acceptable dallisgrass desiccation, improved early ryegrass production, and acceptable dallisgrass recovery.