New agronomic practices are emerging in the green cane system to utilize sugarcane (Saccharum officinarum L.) straw for energy cogeneration, which necessitates its removal from the soil surface. This study has three main objectives: (1) evaluate the population dynamics and composition of Jamaican crabgrass (Digitaria horizontalis Willd.) and large crabgrass [Digitaria sanguinalis (L.) Scop.] under different sugarcane straw amounts, with and without herbicide treatment; (2) assess the development of sugarcane under different straw amounts; and (3) determine the amount of sugarcane straw that should be kept on the soil surface after harvest to ensure that it does not compromise the chemical control for Digitaria spp. in ratoon cane in a green cane system. We conducted this research at two experimental sites, one at the beginning and the other during the middle of the harvest season, over a span of 2 yr. Our primary treatments consisted of different amounts of sugarcane straw after harvest on the soil surface (0, 5, 10, and 15 Mg ha−1), while secondary treatments included the herbicide application (sulfentrazone + tebuthiuron for the beginning of harvest season and isoxaflutole + tebuthiuron for the middle of harvest season). The Digitaria spp. exhibited higher density (four times more) and dry matter (two times more) in scenarios with a lower sugarcane straw amount (5 Mg ha−1) on the soil surface and no herbicide application. However, a higher straw amount (15 Mg ha−1) contributed to reduced Digitaria spp. infestation and to improved sugarcane yield. According to this research, it is essential to maintain at least 10 Mg ha−1 of sugarcane straw on the soil surface and remove only 5 Mg ha−1 for energy cogeneration.

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.

Honey mesquite [Prosopis glandulosa (Torr.) ♯ PRCJG] was treated with several herbicides and herbicide combinations primarily on the Texas Post Oak Savannah over a 4-yr period. Sprays of glyphosate [N-(phosphonomethyl)glycine], picloram (4-amino-3,5,6-trichloropicolinic acid), 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} generally caused a high degree of canopy reduction in the fall of the year the spraying was done. However, sprays of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) and picloram were the most effective herbicides for killing honey mesquite 1 yr after application. At 1.1 kg ai/ha, clopyralid killed 70 to 95% and picloram killed 20 to 65% of plants 3 yr or older. Picloram plus 2,4,5-T was intermediate in effectiveness. Sprays of 2,4,5-T and triclopyr killed some plants. Picloram and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} pellets killed few if any honey mesquite. Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] boluses killed no more than 37% of the honey mesquite at rates up to 4.5 kg ai/ha. Herbicides sometimes killed more honey mesquite with sprouts 2 or 3 yr old than at 1 yr old.

Dicamba (3,6-dichloro-o-anisic acid), 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], 3,6-dichloropicolinic acid, picloram (4-amino-3,5,6-trichloropicolinic acid), triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic 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 applied at rates of 0.3, 0.6, 1.1, and 2.2 kg/ha pre- and postemergence to greenhouse-grown common buffelgrass (Cenchrus ciliaris L. ♯3 PESCI). Buffelgrass tolerated preemergence sprays of 3,6-dichloropicolinic acid up to and including 1.1 kg/ha. All other treatments except picloram and 2,4,5-T at 0.3 kg/ha were phytotoxic to emerging buffelgrass. Buffelgrass tolerated early postemergence applications of 2,4-D, picloram, and tebuthiuron at 0.3 kg/ha; dicamba and 2,4,5-T at 0.6 kg/ha; and 3,6-dichloropicolinic acid at 2.2 kg/ha based on oven-dry shoot production 1 month after treatment. Regrowth of buffelgrass from stubble 1 month after original harvest of the early postemergence treatment occurred only with all rates of 3,6-dichloropicolinic acid and 2,4,5-T at 0.3 kg/ha. When treated at 45 days after planting, buffelgrass tolerated dicamba, 2,4-D, 2,4,5-T, 3,6-dichloropicolinic acid, and picloram at 2.2 kg/ha, but top growth production was significantly reduced by most rates of hexazinone and tebuthiuron. Relative differences in regrowth of buffelgrass 1 month after the original harvest were similar to those of the original harvest. Mature buffelgrass (90 or 150 days old) responded similarly to herbicides as the 45-day-old buffelgrass.

Controlled burning during winter reduced densities of common goldenweed [Isocoma coronopifolia (Gray) Greene] by 33 to 44% and suppressed canopy cover and height of surviving common goldenweeds for 2 yr. Applied to an unburned infestation, 2,4-D [(2,4-dichlorophenoxy) acetic acid] or dicamba (3,6-dichloro-o-anisic acid) granules only partially controlled common goldenweed at rates of 2 kg/ha or less. Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} or picloram (4-amino-3,5,6-trichloropicolinic acid) pellets provided excellent control of common goldenweed if applied at 2 kg/ha during March and at 1 kg/ha if applied after burning in February. The burning pretreatment appeared to synergistically enhance effectiveness of herbicides applied at relatively low rates. Increases in standing crop of buffelgrass (Cenchrus ciliaris L.) following burning were usually small and temporary, but effective herbicide treatments and burn-herbicide combinations increased buffelgrass standing crop by as much as three-fold.

Soil-active herbicides were investigated for control of live oak (Quercus virginiana Mill.) on the Texas Coastal Prairie and Claypan areas with and without mechanical treatment. Roller chopping before, during, or after herbicide application had very little influence on mortality of live oak compared to the herbicide applied alone. Roller chopping did allow increased grazing of livestock for at least 3 yr after knockdown of the brush. Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} was generally the most effective herbicide for live oak control; bromacil (5-bromo-3-sec-butyl-6-methyluracil), karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1,1-dimethylurea], and picloram (4-amino-3,5,6-trichloropicolinic acid) were somewhat less effective, especailly at 2.2 kg/ha. Limited data suggested that hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl]-1,3,5-triazine-2,4(1H,3H)-dione] also was highly effective for control of live oak. Primary invaders on either mechanically or chemically treated areas were American beautyberry (Callicarpa americana L.), southern dewberry (Rubus trivialis Michx.), boneset (Eupatorium perfoliatum L.), yankeeweed (Eupatorium compositifolium Walt.), brownseed paspalum (Paspalum plicatulum Michx.), and carpetgrass (Axonopus affinis Chase). A herbicide was generally equally effective for live oak control whether applied broadcast or in rows as granules, or applied as sprays to the soil surface or subsurface.

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.

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.

Tebuthiuron, picloram, hexazinone, and bromacil were evaluated at 0.5, 1.0, and 2.0 g ai or ae per plant for sacahuista control on gravelly loam soils in western Texas. Tebuthiuron applied at 2.0 g per plant killed 87% of the sacahuista, which was significantly greater mortality than that achieved with the same rate of bromacil (62%) and hexazinone (44%). The 2.0 g plant-1 rate of tebuthiuron, bromacil, and hexazinone reduced live canopies of sacahuista 88 to 98%. Picloram did not control sacahuista. Sacahuista mortality increased curvilinearly with increasing rates of tebuthiuron and bromacil, whereas the response to hexazinone was linear.

Picloram was applied broadcast on kleingrass pastures in the spring either as sprays or as pellets containing 2, 5, or 10% ae. The carrier in 5 and 10% pellets was inert clay, but 2% pellets were formulated with sufficient ammonium sulfate to contain 14.4% N. Dry formulations of picloram (10% ae), dicamba (5% ae), and tebuthiuron (20% ai) were compared to sprays at equal rates in a coastal bermudagrass pasture. Picloram was more effective as a spray than as pellets in two of five experiments. Few differences in weed control were observed with 2, 5, and 10% picloram pellets. Picloram applied up to 3 kg ae/ha as 2% pellets did not reduce kleingrass standing crop and up to 29 kg/ha of N as ammonium sulfate applied with or without picloram did not increase kleingrass production. None of the herbicides controlled weeds during the year following application.

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.

Brush control and woody plant community structure in the Cross Timbers of Oklahoma resulting from treatments with herbicides and fire were compared. Tebuthiuron and triclopyr were applied alone and in combination with burning at 2.2 kg ai ha-1 in March and June of 1983, respectively. The burned pastures were burned with strip headfires in late spring of 1985, 1986, and 1987. Both herbicides were effective on the dominant overstory brush species, blackjack oak and post oak, and this resulted in good reduction of canopy cover of brush initially. However, effects of triclopyr were short-lived because of ineffectiveness on many of the other hardwood species (American elm, gum bumelia, hackberry, roughleaf dogwood, and buckbrush). Crown reduction and tree kill of these hardwood species was usually better with tebuthiuron than with triclopyr. Neither herbicide was effective on eastern redcedar. Better brush control, associated with tebuthiuron, resulted in better fine fuel release and by 1988, burning was having a significant effect on woody plants in the tebuthiuron-treated plots.

Multiflora rose was defoliated completely 320 days after spring foliar application of metsulfuron. Metsulfuron and 2,4-D plus dicamba spring foliar applied controlled multiflora rose equally. Metsulfuron applied to soil using a spotgun at 20 mg per m diam of multiflora rose in the spring resulted in 95% control 320 days later in one study but only 50% control in another. Control was less when lower rates of metsulfuron were soil-applied with a spotgun. Tebuthiuron spring soil-applied completely controlled multiflora rose. All spring-applied foliar and soil applications seemed to control multiflora rose better than fall treatments.

Aerial applications of pelleted tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N, N′-dimethylurea} at 1 kg/ha to rangeland reduced canopy cover of the subshrub false broomweed (Ericameria austrotexana M.C. Johnst.) by 69 to 78%. Complete control was obtained with 2 kg/ha of tebuthiuron. Picloram (4-amino-3,5,6-trichloropicolinic acid) pellets applied at 2 kg/ha controlled false broomweed in two of four experiments; effectiveness of soil-applied picloram appeared to depend upon sufficient rainfall to move the herbicide into the soil soon after treatment. After the first growing season following application, density of herbaceous species tended to be higher in plots receiving either herbicide than in untreated plots. Picloram suppressed curlymesquite [Hilaria berlangeri (Steud.) Nash], but had little effect on other components of the herbaceous vegetation. Abundance of curlymesquite increased substantially following applications of tebuthiuron, at the expense of annual and short-lived perennial grasses and herbaceous broadleaf species.

Seven herbicides were applied to the soil surface or subsurface for control of honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] and Macartney rose (Rosa bracteata Wendl.). Liquid formulations were applied in bands about 1 cm wide, 1.2 m or more apart, and granule or sphere formulations were applied on the soil surface either broadcast or in rows 1.2 m or more apart. On honey mesquite, karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxy-phenyl)-1,1-dimethylurea] and tebuthiuron {N-[5-(1,1-dimethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} were the most effective herbicides with subsurface spray injections being generally more effective than surface applications. On honey mesquite, differences among row spacing treatments with liquid, granule, or sphere formulations of karbutilate were generally either small or insignificant. Roller chopping reduced the honey mesquite canopy but did not influence the percentage of plants killed by karbutilate at rates of 4.5 kg/ha and below. Bromacil (5-bromo-3-sec-butyl-6-methyluracil), diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], picloram (4-amino-3,5,6-trichloropicolinic acid), prometon [2,4-bis(isopropylamino)-6-methoxy-s-triazine], and 2,3,6-TBA (2,3,6-trichlorobenzoic acid) generally were ineffective as soil treatments for controlling honey mesquite. Of all the herbicides evaluated on Macartney rose, only picloram at 4.5 kg/ha and tebuthiuron at 2.2 and 4.5 kg/ha, as soil treatments, killed a significant number of plants.

The responses of whitebrush (Aloysia lycioides Cham.) and several associated species to herbicides were evaluated in the Central Basin and South Plains of Texas. At Llano, hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione], picloram (4-amino-3,5,6-trichloropicolinic acid), and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} were the most effective herbicides for whitebrush control. Picloram was the most effective herbicide on Lindheimer pricklypear (Opuntia lindheimeri Engelm.), tasajillo (Opuntia leptocaulis DC.), Texas colubrina [Colubrina texensis (Torr. & Gray) Gray], and Texas persimmon (Diospyros texana Scheele). Hexazinone, karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1,1-dimethylurea], and tebuthiuron controlled live oak (Quercus virginiana Mill.). Tebuthiuron pellets were slightly more effective on whitebrush when applied broadcast than when applied in rows 1.8 to 6.0 m apart. Roller chopping alone did not kill whitebrush nor improve effectiveness of tebuthiuron but did improve access to the land and visibility for 3 yr. Picloram applied either as the undiluted liquid formulation or as granules was the most effective herbicide for controlling a spectrum of species, including whitebrush. Picloram pellets were generally more effective on Lindheimer pricklypear and Texas persimmon when applied broadcast than when applied in rows. However, tebuthiuron was the most effective herbicide on blackbrush acacia (Acacia rigidula Benth.) and huisache [Acacia farnesiana (L.) Willd.], especially when applied in rows rather than broadcast.

Live oak (Quercus virginiana Mill. # QUEVM) on the Texas Coastal Prairie was treated with herbicides using ground and aerial application methods. Tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} and pellets of buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone} at 2.2 kg ai/ha were the most effective herbicides, killing 60 to 95% of the live oak. Tebuthiuron pellets 3.2 mm in diam were more effective than the wettable powder at 1.1 kg/ha. Bay Met 1486 {N-[5-(ethylsulfonyl)-1,3,4-thiadiazole-2-yl]-N,N′-dimethylurea}, Dowco 290 (3,6-dichloropicolinic acid), hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H, 3H)-dione], and picloram (4-amino-3,5,6-trichloropicolinic acid) reduced the live oak canopy at 2.2 kg/ha whereas 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} were ineffective. Foliage-active herbicides generally were most effective in reducing the live oak canopy during the year of application. The soil-active herbicides generally were most active 1 or 2 yr after herbicide application. All herbicides reduced the live oak cover sufficiently to allow an increase in grass cover 2 to 4 months after treatment. Tebuthiuron at 2.2 kg/ha maintained a high degree of grass cover at least 2 or 3 yr after treatment.

Tebuthiuron was applied at 1 kg ai/ha to wet and dry Hathaway gravelly, sandy loam soil in the spring and fall to determine the amount of tebuthiuron removed in runoff water and the depth to which it would move within the soil profile by simulated rainfall. When pellets containing 20% ai of tebuthiuron were broadcast onto dry soil in the spring, the first simulated rainfall event, 37 mm, removed 5% of the applied tebuthiuron in runoff water and sediment. The second and third simulated rainfall events, 22 and 21 mm, respectively, removed an additional 2%. When tebuthiuron was applied to wet soil in the spring, the initial simulated rainfall events, totaling 42 mm, removed 15% of the tebuthiuron. When tebuthiuron was applied to wet soil in the fall, the initial rainfall events, totaling 40 mm, removed a total of 48% of the tebuthiuron in runoff water and sediment. No significant differences were found in the total amount of tebuthiuron within the soil profile after application to dry and wet soils. More than half of the tebuthiuron had moved into the surface 7 cm 1 day after application. Tebuthiuron was not detected below 90 cm after 165 mm of simulated rainfall and 270 mm of natural rainfall.

Until recently melaleuca was spreading at a rate faster than it was being controlled throughout the boundaries of the South Florida Water Management District (District). Although melaleuca is a difficult species to eradicate, apparently District efforts, along with those of other governmental agencies and private groups, are containing its spread within the Everglades Water Conservation Areas (WCAs) and the marsh of Lake Okeechobee. Melaleuca has been completely cleared from WCA-2A, -3B, and -3A, south of Alligator Alley. These areas are now under “maintenance control.” Maintenance control means applying management techniques in a continuous basis to keep an invasive plant population at its lowest feasible level. Today, the melaleuca infestation is no longer increasing; in many areas, it is being reduced. Preliminary results from the latest District survey indicate melaleuca infestation has decreased considerably in South Florida, especially in public lands. The intent of this paper is to provide an assessment of progress made by the District's melaleuca control program over the past 7 yr.