Total vegetation control (TVC) is an essential management practice to eliminate all vegetation for the purpose of protecting infrastructure, people, or natural resources on sites where vegetation poses major fire, visibility, and infrastructure risks. TVC is implemented on sites such as railroads, power substations, airports, roadsides, and oil and gas facilities. Current research has identified that tank-mixing two effective mechanisms of action is a superior resistance management strategy compared to rotating mechanisms of action; however, effective tank mixes for TVC have not been thoroughly evaluated. A field experiment was conducted from 2013 to 2014 at five sites in Colorado to compare 32 treatment combinations to two industry standards for TVC. Research objectives were (1) to identify herbicide tank-mix combinations for TVC with multiple effective mechanisms of action for resistance management, (2) to evaluate lower use rate alternatives to minimize nontarget impacts, and (3) to determine the efficacy of fall versus spring application timings. Seven treatments were identified as top-ranking treatments, averaging 96% bare-ground (BG) across five sites and two application timings. Four out of the seven top-ranked treatments included aminocyclopyrachlor, chlorsulfuron, and indaziflam. The industry standard diuron plus imazapyr was in the top ranking, whereas the other industry standard bromacil plus diuron performed inconsistently across sites. Probability modeling was used to predict the probability of achieving 97% or 100% BG with various treatment combinations. The combination of aminocyclopyrachlor, chlorsulfuron, indaziflam, and imazapyr had the highest predicted BG probability, with 88% predicted probability of achieving 100% BG, compared to 67% and 52% predicted probabilities for the industry standards diuron plus imazapyr and bromacil plus diuron, respectively. In three of the five sites, fall applications outperformed the same treatments applied in the spring. Several top-ranking treatments represent newer, lower use rate herbicide combinations that provide multiple mechanisms of action to manage herbicide-resistant weeds and minimize nontarget impacts.

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.

Interactions of water-soluble soil organic matter (WSSOM) with the herbicides bromacil, metribuzin, alachlor, diquat, and paraquat were examined to determine if these interactions can improve predictions of herbicide leaching potential. A high-performance liquid chromatography gel filtration column was used to separate WSSOM extracts from four mineral agricultural soils into fractions with approximate log molecular weights of 4.96 to 6.82. WSSOM fractions were predominantly anionic in nature with some hydrophobic character. The amount of paraquat bound by WSSOM ranged from 1.1 to 2.1 mmol g−1DOC−1 with KDOC (partition coefficient for dissolved organic carbon) values from 0.050 to 0.187 L kg−1. Diquat was bound at 0.9 to 1.5 mmol g−1DOC−1 by the extracts with KDOC values from 0.044 to 0.143 L kg−1. Bromacil, metribuzin, and alachlor did not bind to the extracts tested. WSSOM did not increase paraquat solubility in the presence of soil. Binding of these herbicides to WSSOM in the soils used in this study would not be a significant mechanism for increased mobility and groundwater contamination potential.

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.

Field studies of herbicidal antagonism were conducted in corn (Zea mays L.), soybeans (Glycine max L. Merr.), and on industrial sites. The addition of chlorbromuron [3-(4-bromo-3-chlorophenyl)-1-methoxy-1-methylurea], cyanazine {2-[[4-(chloro-6-(ethylamino)-s-triazin-2-yl] amino]-2-methylpropionitrile}, bifenox [methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate], or atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] wettable powder plus dicamba (3,6-dichloro-o-anisic acid) to glyphosate [N-(phosphonomethyl)glycine]-alachlor[2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] combinations reduced the activity of glyphosate on quackgrass [Agropyron repens (L.) Beauv.], common dandelion (Taraxacum officinale Weber), and Canada thistle [Cirsium arvense (L.) Scop.] in no-till corn. Reduced weed control from antagonism resulted in decreased corn yields. Linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], chlorbromuron, or metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], when added to glyphosate, reduced the control of quackgrass but not that of Canada thistle, alfalfa, or common dandelion in soybeans. Antagonsim was not evident in annual weed species. In perennial weeds, the degree of antagonism was often reduced with increased dosages of glyphosate. The inclusion of terbacil (3-tert-butyl-5-chloro-6-methyluracil), bromacil (5-bromo-3-sec-butyl-6-methyluracil), and simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] with glyphosate in mixes interfered with the control of smooth brome (Bromus inermis Leyss.), but not when applications of the residual herbicides were delayed. Quackgrass control was reduced when amitrole (3-amino-s-triazole) was mixed with glyphosate, or when applied separately.

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.

Granule, and in some cases, tablet and ball formulations of bromacil (5-bromo-3-sec-butyl-6-methyluracil), dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid), karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxyphenyl)-1,1-dimethylurea], and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethyl urea} were applied to three areas within 30 km of College Station in the Claypan Resource area of Texas. Woody species growing in the area included blackjack oak (Quercus marilandica Muenchh.), post oak (Quercus stellata Wangenh.), yaupon (Ilex vomitoria Ait.), winged elm (Ulmus alata Michx.), white ash (Fraxinus americana L.), mockernut hickory (Carya tomentosa Nutt.), and tree huckleberry (Vaccinium arboreum Marsh.). Granules were applied either broadcast or in rows at several intervals. Tebuthiuron was the most effective herbicide on oaks, winged elm, and white ash. Tebuthiuron and picloram were equally and most effective on yaupon, mockernut hickory, and tree huckleberry. Tebuthiuron + picloram at 2.2 + 2.2 kg/ha was the most effective herbicide treatment on huckleberry. However, a mixture of tebuthiuron + picloram (1:1 w/w) was usually no more effective than the same rate of tebuthiuron in the mixture applied alone. Tablet and ball formulations of karbutilate and tablet formulations of tebuthiuron were generally equally as effective as granules. Applications of picloram and tebuthiuron granules in rows 1.8, 3.0, 4.6, or 6.1 m apart gave control equal to broadcast applications except for picloram on yaupon. On yaupon all row spacing treatments of picloram were less effective than the broadcast treatment, whereas with tebuthiuron the 6.1-m spacing was least effective. Picloram and tebuthiuron granules applied in rows, approximately at 1.8-m intervals with a tractor, were as effective as granules applied by hand in straight rows.

The response of potted ‘Cleopatra’ mandarin citrus seedlings to metalaxyl applied as a mixture with metolachlor, simazine, or bromacil, or as a sequential application after the herbicides was investigated under screen house conditions. The soils were drenched with herbicides at 2.5 ppmw (mg kg−1 soil dry wt basis) in tank-mixes with metalaxyl or metalaxyl was applied as a soil drench at 5, 50, and 250 ppmw 1, 2, 3, and 4 wk after herbicide application. Citrus seedling response to treatment was dependent on the presence or absence of herbicide, metalaxyl concentration, and the time following application. Fresh weights of citrus treated with 5 ppmw metalaxyl after herbicide application were no different from those treated with the mixture. Metalaxyl at 5 and 50 ppmw alone or with metolachlor did not affect citrus seedling fresh weight. However, delaying metalaxyl application at 50 ppmw by 3 or 4 wk after simazine and bromacil increased citrus seedling fresh weight as compared with the tank-mix. Separate applications of metalaxyl at 250 ppm reduced citrus seedling fresh weight less than the mixture for all the herbicides.

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.

Solar heating (SH) of the soil by mulching it with transparent polyethylene (PE) during the hot season elevated the soil temperature by 10 to 18 C above that of the non-mulched soil. SH for 4 to 5 weeks resulted in effective control of most summer and winter annual weeds, the effect lasting for more than 5 months after PE removal. Melilotus sulcatus Desf., Astragalus boeticus L. and bull mallow (Malva nicaeensis All. # MALNI) were not controlled by SH. Perennial weeds which propagate from vegetative parts were only partially controlled with short SH, but mulching for 8 to 10 weeks improved control. Mulching the soil with perforated or shaded transparent PE or black PE resulted in a smaller increase of soil temperature and thus less efficient weed control. A combination of SH with soil-incorporated EPTC (S-ethyl dipropylthiocarbamate) or vernolate (S-propyl dipropylthiocarbamate) did not improve the weed control over SH alone, but significantly enhanced the disappearance of the herbicides from the soil. SH inhibited the disappearance of fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl) phenyl]-4(1H)-pyridinone} but did not change the residual phytotoxicity of bromacil (5-bromo-3-sec-butyl-6-methyluracil). SH treatment improved plant growth and increased the yield of wheat (Triticum aestivum L. ‘895′) and turnip (Brassica rapa L. ‘Purple top’), but not of parsley (Petroselinum sativum Hoffm.).

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.

Under unsaturated-flow conditions, bromacil (5-bromo-3-sec-butyl-6-methyluracil) was considerably more mobile than buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxyl-1-methyl-2-imidazolidinone}. Because of their high water solubilities, both herbicides were much more mobile than atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), prometon [2,4-bis (isopropylamino)-6-methoxy-s-triazine], or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea]. Under saturated-flow conditions, buthidazole was leached through Lakeland loamy sand in slightly greater amounts than tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} or CN-10-3510 (formerly VEL 3510) {1-β,β-dimethoxyl-1-methyl-3-[5-(1,1-dimethylethyl)-1,3, 4-thiadiazol-2-yl] urea}. Distribution of the three herbicides in the leached soil was similar and relatively uniform. In Lakeland loamy sand, 30 times as much tebuthiuron was leached under saturated-flow conditions as under unsaturated-flow conditions. Intermittent saturated-unsaturated-flow conditions resulted in four times as much leaching of tebuthiuron as unsaturated flow alone. Only one-tenth as much tebuthiuron leached under intermittent saturated-unsaturated-flow conditions as under saturated-flow conditions. Tebuthiuron added to Lakeland soil and oven-dried was retained in significantly greater amounts than when added to moist Lakeland soil. Low amounts of tebuthiuron leached through Lakeland loamy sand, Portsmouth sandy loam, and Rains silt loam, but high amounts leached through Davidson clay. Greater amounts of the herbicide were retained in the surface zones of the three former soils, but the inverse was the case for the Davidson soil.

Bromacil (5-bromo-3-sec-butyl-6-methyluracil), glyphosate (N-phosphonomethylglycine), picloram (4-amino-3,5,6-trichloropicolinic acid), simazine [2-chloro-4,6-bis (ethylamino)-s-triazine], and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] were evaluated at four application rates and five application dates, May 1, June 1, July 1, August 1, and September 1, for their ability to control seven herbaceous, forest ground covers, hayscented fern (Dennstaedtia punctilobula (Michx.) Moore), New York fern (Thelypteris noveboracensis L.), short husk grass (Brachyelytrum erectum Schreb.), bracken fern [Pteridium aquilinum (L.) Kuhn var. latiusculum (Desv.) Underw.], wild oat grass (Danthonia compressa Aust.), rough goldenrod (Solidago rugosa Mill.), and flattop aster (Aster umbellatus Mill.) without residual effects on black cherry (Prunus serotina Ehrh.) seed stored in the forest floor, or on survival and growth of natural or planted black cherry seedlings. Control of most of the target species depended on the date and rate of application. Simazine had no herbicidal effect on these extremely acid (pH 3.9 to 4.4) Allegheny Plateau sites. None of the herbicides interfered with germination of black cherry seed stored in the forest floor or with establishment of seedlings. Bromacil applied at 22.4 kg/ha, picloram, at 9.0 kg/ha, and hexazinone at 13.4 kg/ha reduced survival, or growth, or both, of black cherry seedlings planted in a forest opening. Glyphosate was the most economical herbicide that met the control criteria. Application of 1.1 kg/ha between August 1 and September 1 produced acceptable control of all target species for at least 3 yr.

Nine herbicides were tested in a field trial during 2001 and 2002 for the ability to suppress growth of established plants of yellow old world bluestem (OWB) that had invaded native vegetation in central Kansas. Herbicide treatments were applied to OWB at the V4 stage of growth using the Nebraska staging method. At 9 wk after treatment (WAT), plots treated with imazapyr at 1.40 kg ai/ ha had much lower OWB plant frequency than the untreated plots, and plots sprayed with imazapyr and bromacil at 7.84 kg ai/ha had much lower OWB tiller densities than the control plots. Imazapyr and glyphosate at 3.36 kg ai/ha provided greater OWB control than other herbicides. At the first frost after treatment application, imazapyr and bromacil treatments continued to have lower OWB frequency and tiller density than the control plots. Visible herbicide control was closely related to end-of-season yield (R = −0.97). Imazapic at 0.16 kg ai/ha, glyphosate, sulfometuron at 0.21 kg ai/ ha, bromacil, and imazapyr controlled OWB from 54 to 94%. Split applications, altered timing of herbicide application, or varied rates of herbicides that exhibited suppressive potential may further improve efficacy of these herbicides.

Soil-applied herbicides are commonly used for broad-spectrum residual weed control in Florida citrus. Groundwater contamination from some soil-applied herbicides has been reported in citrus growing areas in Florida. Indaziflam is a new soil-applied herbicide recently registered for broad-spectrum weed control in Florida citrus. There is no information available on leaching behavior of indaziflam in sandy soil. Experiments were conducted to compare leaching of indaziflam with five commercially used residual herbicides in a Florida Candler soil under simulated rainfall of 5 or 15 cm ha−1. Herbicide movement down soil columns was measured by visually evaluating injury and harvesting aboveground biomass of the bioassay species annual ryegrass. Ryegrass was not injured and plant biomass was not affected beyond 30 cm when indaziflam at a recommended rate of 73 g ai ha−1 was leached through the soil column. Leaching of indaziflam increased with increasing amounts of rainfall. For example, indaziflam leached up to 12.2 ± 0.8 cm (values are expressed ± SD) and 27.2 ± 2.6 cm at 5 and 15 cm ha−1 rainfall, respectively. The herbicide ranking from high to low mobility at 15 cm ha−1 of rainfall was bromacil = norflurazon > indaziflam > simazine = pendimethalin > diuron. Overall results suggested that indaziflam leaching was limited in Florida Candler soil in this study; however, field experiments are required to confirm the leaching of indaziflam under natural rainfall situation.

In citrus, weedy grasses compete for moisture, nutrients, and light and can inhibit the growth of young trees and delay fruit production. These weeds are difficult to control, either because of their tolerance to available herbicides or due to growth habits that enable them to resist other control practices. Control of seven such weedy grasses (southern sandbur, large crabgrass, crowfootgrass, guineagrass, Texas panicum, johnsongrass, and yellow foxtail) with a mixture of three fungal pathogens, termed the multiple-pathogen strategy, was field tested in 1996 and 1998. Three fungi indigenous to Florida, Drechslera gigantea, Exserohilum longirostratum, and E. rostratum, isolated from large crabgrass, crowfootgrass, and johnsongrass respectively, were used. Two separate field studies were conducted: one study with seven grasses transplanted and grown within each plot (grass mixture field trial) and another study on a population of guineagrass alone present in a naturally infested field (guineagrass field trial). The objectives of this study were to (1) evaluate the field performance of D. gigantea, E. longirostratum, and E. rostratum individually and in a mixture to control the seven transplanted weedy grasses (grass mixture) and a population of guineagrass in a naturally infested field, respectively, and (2) compare the effectiveness of three carriers (water, Metamucil®, and an invert emulsion) on the bioherbicidal efficacy under field conditions. The fungi were applied as foliar sprays, each pathogen alone or in a mixture of the three fungi (1:1:1, v/v/v, for a total of 5 × 105 spores ml –1) in water, 0.5% aqueous Metamucil®, or an emulsion containing Sunspray® 6E. During the 14-wk experimental period, one or two additional sprays of all treatments were applied. Disease severity was recorded weekly for 4 to 6 wk after the initial spray (WAI). Maximum disease severities were obtained in emulsion-inoculum treatments, and were higher than those in the water-inoculum and the Metamucil-inoculum treatments. The pathogen mixture was equally effective as the individual pathogens in controlling the weeds tested. In the 1996 trial, 6 WAI, disease severity on grasses inoculated with D. gigantea spore suspensions in emulsion ranged from 78 to 100%, with E. longirostratum 90 to 100%, E. rostratum 79 to 100%, and the mixture 74 to 100%. In the 1998 trial, 4 WAI, disease severity on grasses inoculated with D. gigantea spore suspensions in emulsion ranged from 45 to 98%, with E. longirostratum 45 to 98%, E. rostratum 34 to 98%, and the mixture 32 to 98.5%. Thus, it was possible to manage all seven weedy grasses under field conditions using an emulsion-based inoculum preparation with the individual pathogens as well as the mixture of pathogens. The same three fungal pathogens were field tested for their ability to manage populations of guineagrass in a naturally infested field. The experimental design and treatments were identical to the field testing with the seven transplanted grasses. Two applications of an emulsion-based inoculum preparation of each pathogen or the mixture of pathogens effectively controlled guineagrass for up to 10 wk, with no regrowth.

Kochia poses a challenge to vegetation management in both agricultural and noncrop areas. This species has developed widespread resistance to several herbicides with differing modes of action, including acetolactate synthase inhibitors and photosynthesis inhibitors. Resistance is also beginning to appear against the synthetic auxins and glycines. Therefore, alternative PRE and POST herbicides are needed for effective kochia management, especially in roadside bare-ground zones. Both PRE and POST herbicides were screened on rights-of-way in Pennsylvania. Mixtures containing diuron, flumioxazin, sulfentrazone, pendimethalin, prodiamine, and bromacil were evaluated for PRE activity in combination with glyphosate. POST kochia control was assessed for 15 noncrop herbicides. Results from all trials varied with kochia size and vigor at time of treatment. Although diuron is the current industry standard for PRE control in tank mixes, sulfentrazone appeared to have the most POST activity against vigorously growing kochia. All PRE herbicides evaluated performed better than the standard, sulfometuron plus chlorsulfuron alone. Dicamba, dicamba plus diflufenzopyr, fluroxypyr, and glyphosate performed best against kochia when applied POST. The recently available chemistries saflufenacil and aminocyclopyrachlor require further evaluation of application timing and use rates, respectively, for POST activity on kochia.