Drill-interseeding cover crops into standing corn (V3 to V5 growth stage) provides opportunities for increasing functional diversity in cropping systems by facilitating use of cover crop mixtures that include grass, legume, and brassica species. Designing herbicide-based weed control programs that negotiate tradeoffs between crop protection and environmental goals when interseeding mixtures remains a major challenge. The objective of this study was to use greenhouse-based dose-response assays to describe the relative sensitivity of 12 cover crop species that differ in traits, including taxonomic group and seed mass, to chloroacetamide (acetochlor, dimethenamid, S-metolachlor; Group 15 herbicides as categorized by the Weed Science Society of America) and pyrazole (pyroxasulfone; Group 15) herbicides. Nonlinear models were fit, and effective doses were estimated (ED50) to compare relative sensitivities of cover crop species to each herbicide. Brassica species (winter canola, Dwarf Essex rape, daikon radish) were less sensitive than small-seeded legumes (medium red clover, crimson clover) and grasses (annual ryegrass) in response to each chloroacetamide, but similar in response to pyroxasulfone. Austrian winter pea, a large-seeded legume, was less sensitive to each herbicide compared to other legumes (crimson clover, medium red clover, hairy vetch). Cereal rye and triticale were less sensitive to dimethenamid, S-metolachlor, and pyroxasulfone compared to annual ryegrass, but similar sensitivities were observed for acetochlor. These results suggest that relative differences in sensitivity to chloroacetamide and pyrazole herbicides could be exploited when designing cover crop mixtures for interseeding. It is imperative, however, to use these findings in conjunction with field-based observations of cover crop injury potential in interseeded systems.

This study was undertaken to investigate the integration effects of pretilachlor, oxadiazon, and dimethenamid with or without glyphosate in a stale seedbed method to control weedy rice in wet-seeded rice. The study, conducted in 2018 and 2019, comprised two seedbed treatments in main plots, with and without glyphosate (850 g ae ha−1), and four subplot treatments: pretilachlor, oxadiazon, dimethenamid, and unsprayed check. Fifteen days after glyphosate spray, each subplot was treated with preemergence herbicides at 500 g ai ha−1 under standing water conditions (2 to 3 in.), and the water level was maintained for 7 d. Pregerminated rice seeds (var. MR297) were hand-broadcasted in the moist soil at 120 kg ha−1 seeding rate. In 2019, the density and dry weight of weedy rice were 30% and 118% higher Gthan those observed in 2018, respectively. A stale seedbed with glyphosate reduced weedy rice dry weight by 12% as compared to what was observed in a stale seedbed without glyphosate. Addition of oxadiazon and pretilachlor to the stale seedbed drastically reduced weedy rice dry weight by 70% to 88% and 53% to 60% in both years. Dimethenamid contributed to a significant reduction of weedy rice dry weight of 19% in 2019 only but failed to provide a positive economic return. Integration of pretilachlor and oxadiazon in a stale seedbed with glyphosate gave profitable returns of $84.00 to 311.4 ha−1 and $175.70 to 483.8 ha−1, respectively. Without the presence of glyphosate, pretilachlor and oxadiazon contributed a positive return of $318.90 and $469.40, respectively, in 2018, but the economic returns were negative in 2019. These results suggest that integration of pretilachlor or oxadiazon in a stale seedbed with glyphosate is more crucial when weedy rice infestation is high, but glyphosate can be excluded from the management regime when the weedy rice populations are low.

Praxelis is an annual to short-lived perennial herb in the Asteraceae family and an emerging problematic weed species in Florida nurseries. The objective of these experiments was to determine efficacy of selected PRE and POST herbicides for control of praxelis. An additional experiment was conducted to determine efficacy of the same PRE herbicides for control of bluemink, a weed similar in appearance to praxelis that is also common in Florida. The granular herbicides dimethenamid + pendimethalin, flumioxazin, oxyfluorfen + pendimethalin, oxyfluorfen + prodiamine, and trifluralin + isoxaben were evaluated, along with spray-applied formulations of dimethenamid, indaziflam, and prodiamine + isoxaben. Flumioxazin consistently provided over 90% control of praxelis at both sites. Indaziflam control was inconsistent between the two sites, providing 100% control in Apopka but only a 22% reduction in weed counts in Balm. Oxyfluorfen + pendimethalin, oxyfluorfen + prodiamine, and prodiamine + isoxaben also provided control (57% to 97% reduction in shoot weight), albeit generally to a lesser degree than was observed with flumioxazin. All PRE herbicides provided similar control of both praxelis and bluemink, with the exception of dimethenamid and dimethenamid + pendimethalin, which reduced bluemink shoot weight more than praxelis. Clopyralid, glyphosate, and triclopyr all provided effective POST control of mature and flowering praxelis through 12 wk after treatment (WAT) and resulted in greater praxelis control than glufosinate. Results suggest that many commonly used PRE and POST herbicides would provide control of praxelis, but use of PRE and POST herbicides as well as sequential applications may be needed for long-term management.

The dissipation of four commonly used soil-applied herbicides was examined in a standardized field experiment in three southern states (Kentucky, Mississippi, and Tennessee). Averaged over the three soils and 2 yr, the relative order of increasing half-life defined as time for 50% disappearance in days (DT50) was acetochlor (6.3 d) = alachlor (6.3 d) = SAN 582 (7.3 d) < metolachlor (13.7 d). Metolachlor was the most persistent in the soil surface, and this could potentially translate into greater duration of weed control into the growing season. All examined herbicides had a DT50 that averaged less than 14 d in all states in both years, so full-season weed control of susceptible species would not be expected. Rapid herbicide degradation was encouraged in these field sites by adequate to excessive soil moisture and warm temperatures throughout the sampling interval. The soils also were light textured, and the lower adsorption of the herbicide allowed for degradation ease and perhaps leaching below the sampling depth.

Field experiments were conducted in 2008 and 2010 to determine crop tolerance and weed control efficacy of the POST herbicides bentazon, flumioxazin, and oxyfluorfen applied to direct-seeded dry bulb onions on organic soil. Postemergence application of oxyfluorfen at 0.071 kg ai ha−1 resulted in less than 20% onion injury when applied at the 2 and 4 onion leaf stages and provided good control of ladysthumb and common lambsquarters. Oxyfluorfen EC caused slightly higher visual injury than oxyfluorfen SC, but there was no difference in onion yield among the treatments. Application of flumioxazin at 0.036 of 0.072 kg ai ha−1 alone or in combination with pendimethalin ACS resulted in minimal onion injury and no yield reduction. Combining flumioxazin in a tank mix with pendimethalin EC, dimethenamid-P EC, or S-metolachlor EC resulted in significant onion injury and yield reduction. Flumioxazin plus S-metolachlor, dimethenamid-P, or pendimethalin improved ladysthumb control in one of two years. Bentazon applied at 0.56 kg ai ha−1 produced moderate onion injury and did not control yellow nutsedge adequately. Bentazon applied at 1.12 kg ai ha−1 provided good control of yellow nutsedge but caused serious onion injury and yield loss.

Glyphosate-resistant (GR) common waterhemp has become a significant problem weed in Nebraska and several Midwestern states. Several populations of GR common waterhemp are also resistant to acetolactate synthase (ALS)-inhibiting herbicides, making them difficult to control with POST herbicides in GR soybean. Glufosinate-resistant (GFR) soybean is an alternate system for controlling GR common waterhemp, justifying the need for evaluating glufosinate-based herbicide programs. The objectives of this study were to compare POST-only herbicide programs (including one-pass and two-pass POST programs) with PRE followed by (fb) POST herbicide programs for control of GR common waterhemp in GFR soybean and their effect on common waterhemp density, biomass, and soybean yield. Field experiments were conducted in 2013 and 2014 near Fremont, NE in a grower’s field infested with GR common waterhemp. Glufosinate applied early- and late-POST provided 76% control of GR common waterhemp at 14 d after late-POST (DALPOST) compared with 93% control with a PRE fb POST program when averaged across treatments. The PRE application of chlorimuron plus thifensulfuron plus flumioxazin, S-metolachlor plus fomesafen or metribuzin, saflufenacil plus dimethenamid-P fb glufosinate provided ≥95% control of common waterhemp throughout the growing season, reduced common waterhemp density to ≤2.0 plants m─2, caused ≥94% biomass reduction, and led to 1,984 to 2,210 kg ha─1 soybean yield. Averaged across treatments, the PRE fb POST program provided 82% common waterhemp control at soybean harvest, reduced density to 23 plants m─2 at 14 DALPOST, and caused 86% biomass reduction and 1,803 kg ha─1 soybean yield compared with 77% control, 99 plants m─2, 53% biomass reduction, and 1,190 kg ha─1 yield with POST-only program. It is concluded that PRE fb POST programs with multiple effective modes of action are available for control of GR common waterhemp in GFR soybean.

Field studies were conducted from 1995 through 1998 to evaluate citronmelon control in peanut with various preplant and preemergence combinations of dimethenamid, flumioxazin, imazethapyr, lactofen, metolachlor, oxyfluorfen, and pendimethalin. Pendimethalin alone or in combination with imazethapyr, metolachlor, or dimethenamid did not control citronmelon. Flumioxazin alone, pendimethalin plus flumioxazin, or pendimethalin followed by (fb) lactofen controlled citronmelon at least 85% early season. Pendimethalin fb lactofen controlled citronmelon at least 75% late season, whereas all other herbicide treatments controlled less than 70%.

Atrazine has been the most widely used herbicide in North American processing sweet corn for decades; however, increased restrictions in recent years have reduced or eliminated atrazine use in certain production areas. The objective of this study was to identify the best stakeholder-derived weed management alternatives to atrazine in processing sweet corn. In field trials throughout the major production areas of processing sweet corn, including three states over 4 yr, 12 atrazine-free weed management treatments were compared to three standard atrazine-containing treatments and a weed-free check. Treatments varied with respect to herbicide mode of action, herbicide application timing, and interrow cultivation. All treatments included a PRE application of dimethenamid. No single weed species occurred across all sites; however, weeds observed in two or more sites included common lambsquarters, giant ragweed, morningglory species, velvetleaf, and wild-proso millet. Standard treatments containing both atrazine and mesotrione POST provided the most efficacious weed control among treatments and resulted in crop yields comparable to the weed-free check, thus demonstrating the value of atrazine in sweet corn production systems. Timely interrow cultivation in atrazine-free treatments did not consistently improve weed control. Only two atrazine-free treatments consistently resulted in weed control and crop yield comparable to standard treatments with atrazine POST: treatments with tembotrione POST either with or without interrow cultivation. Additional atrazine-free treatments with topramezone applied POST worked well in Oregon where small-seeded weed species were prevalent. This work demonstrates that certain atrazine-free weed management systems, based on input from the sweet corn growers and processors who would adopt this technology, are comparable in performance to standard atrazine-containing weed management systems.

Field and greenhouse studies were conducted to evaluate herbicides in pumpkin. Field experiments at three Illinois locations determined weed control and crop injury from clomazone, dimethenamid, ethalfluralin, sulfentrazone, imazamox, RPA 201772, flumiclorac, and halosulfuron applied preemergence. Clomazone plus sulfentrazone controlled redroot pigweed 78 to 99%, ivyleaf morningglory 80 to 97%, common lambsquarters 97%, common purslane 84 to 99%, and velvetleaf 55 to 99%. Imazamox plus clomazone commonly provided more consistent broadleaf weed control than did ethalfluralin plus clomazone. RPA 201772 when used on sandy soils killed the pumpkin. Sulfentrazone initially caused chlorosis and necrosis on pumpkin seedlings when soil organic matter was low (< 1%) or when soil moisture was high. However, plants recovered rapidly, and yields were not affected. In a greenhouse study pumpkin was more tolerant to clomazone plus sulfentrazone than to sulfentrazone.

Dry edible bean class and cultivar response to dimethenamid and metolachlor was investigated in the greenhouse and field. Kidney and cranberry cultivars, as well as a small red cultivar, were not injured by dimethenamid applied PRE at 2,100 g ai/ha in the greenhouse, whereas pinto bean tolerance varied and navy and black bean cultivars were injured by this rate. Injury to navy bean was greater in the greenhouse when dimethenamid and metolachlor were placed in the zone above and including the seed, compared with placement in the seed, root, or root plus seed zone. In an application timing field study, dimethenamid at 1,300 g/ha applied at the crook or unifoliate growth stage caused injury to navy bean, delayed maturity, and reduced seed yield. Metolachlor at 1,400 g ai/ha delayed maturity when applied at the unifoliate growth stage but did not reduce seed yield. Dimethenamid or metolachlor PRE, at 1,300 or 2,800 g ai/ha, respectively, injured navy and black bean cultivars, but seed yield was not reduced in a cultivar tolerance field study. In a planting date study, dimethenamid PRE at 2,300 g/ha reduced leaf area and delayed maturity compared with the nontreated control when pooled over five planting dates and cultivars in each of 2 yr. Metolachlor PRE at 2,800 g/ha reduced leaf area in 1 yr and delayed maturity in both years when pooled over planting dates and cultivars. If weed control and herbicide costs are comparable, metolachlor at a standard use rate is a safer choice than dimethenamid for use in navy and black bean production.

Treatments of dimethenamid-p at 0.7 kg ai/ha applied PRE in tank mixtures with EPTC (3.4 kg ai/ha), metribuzin (560 g ai/ha), pendimethalin (1.1 kg ai/ha), or rimsulfuron (26 g ai/ha) were compared with the same herbicides applied PRE alone in field efficacy trials in Idaho, Oregon, and Washington. Common lambsquarters, kochia, and redroot pigweed control was generally improved with dimethenamid-p tank mixtures compared with control by any herbicide applied alone except metribuzin. Hairy nightshade control at two locations was generally improved with tank mixtures compared with control by any herbicide applied alone. At Washington, where row spacing was narrower than at other locations, dimethenamid-p alone or in tank mixtures provided similar hairy nightshade control, and this control was greater than control by EPTC, metribuzin, or pendimethalin applied alone. ‘Alturas’, ‘Bannock Russet’, ‘Ranger Russet’, ‘Russet Burbank’, ‘Russet Norkotah’, and ‘Shepody’ potato tolerance to dimethenamid-p PRE at 0, 0.7, or 1.4 kg ai/ha was assessed in weed-free field trials conducted at Aberdeen, ID, in 2002 and 2003. Little or no crop injury was evident during the growing seasons and there were no reductions in U.S. No. 1 and total tuber yields regardless of dimethenamid-p rate or potato variety.

Field experiments were conducted in 2004 and 2005 to determine the tolerance of direct-seeded green onion to selected herbicides applied before or after green onion emergence. Preemergence herbicides included S-metolachlor, pendimethalin, dimethenamid, quinclorac, pronamide, ethofumesate, and DCPA, a registered standard. Herbicide applied to two- to three-leaf green onion included glyphosate, trifloxysulfuron, flumioxazin, phenmedipham, ethalfluralin, pendimethalin, S-metolachlor, and oxyfluorfen. Plots were cultivated and hand weeded to minimize negative effects of weed interference on the crop. All herbicides applied at seeding, excluding DCPA, caused excessive injury (>25%) to green onion in at least 1 of 2 years. Oxyfluorfen, ethalfluralin, or S-metolachlor applied after crop emergence caused less than 10% injury in both years to green onion. Green onion yields following treatment with oxyfluorfen, ethalfluralin, or S-metolachlor were equivalent to the nontreated control. All other herbicides applied after crop emergence resulted in height, density, or yield reductions relative to a nontreated control in at least 1 of 2 years.

Weed management is a major production issue facing otebo bean growers in Ontario. Field trials were conducted at six Ontario locations during a 2-yr period (2003 and 2004) to evaluate the tolerance of otebo bean to the preplant incorporated (PPI) application of EPTC at 4,400 and 8,800 g ai/ha, trifluralin at 1,155 and 2,310 g ai/ha, dimethenamid at 1,250 and 2,500 g ai/ha, S-metolachlor at 1,600 and 3,200 g ai/ha, and imazethapyr at 75 and 150 g ai/ha. EPTC, trifluralin, dimethenamid, and S-metolachlor applied PPI resulted in minimal (less than 5%) visual injury and with exception of the low rate of dimethenamid causing a 16% reduction in shoot dry weight and the high rate causing an 8% plant height reduction had no adverse effect on plant height, shoot dry weight, seed moisture content, and yield. Imazethapyr applied PPI caused up to 7% visual injury and reduced plant height, shoot dry weight, and yield 8, 18, and 12% at 75 g/ha and 19, 38, and 27% at 150 g/ ha, respectively. Seed moisture content was also reduced by 0.4% with both rates. Based on these results, otebo bean is not tolerant of imazethapyr applied PPI at rates as low as 75 g/ha, the proposed use rate. EPTC, trifluralin, dimethenamid, and S-metolachlor applied PPI have a 2× rate crop safety margin for use in otebo bean weed management.

The extended production of allelochemicals from a living mulch cover crop may potentially enhance weed management and crop productivity compared with traditional zucchini squash production systems. However, the efficacy of a living mulch cover crop in no-tillage (NT) systems with herbicides has not been determined for many vegetable crops. The objective of this research was to evaluate weed management and zucchini squash production using the combination of NT and a herbicide-suppressed winter rye cover crop with or without PRE herbicides. When used in combination with herbicides, the winter rye living mulch reduced the biomass of redroot pigweed compared to the herbicides applied alone, but did not influence the biomass of smooth crabgrass for any herbicide treatment. Visual estimates of weed control were similar for each herbicide treatment with and without the winter rye living mulch. The herbicide-suppressed winter rye resulted in excessive stunting of zucchini squash at 56 d after treatment which correlated with 20 and 50% squash yield reductions for the 2004 and 2005 growing seasons, respectively. Although some squash yield loss may have resulted from direct competition with the winter rye living mulch, yield reductions most likely resulted from allelopathy. The winter rye living mulch was the primary contributing factor for reduced squash yield and did not interact with herbicide treatment. All treatments containing herbicides resulted in yields similar to the weed-free treatment. Because of excessive zucchini injury, this research suggests that the use of herbicide-suppressed winter rye living mulch does not appear to be a feasible option for increased weed control in zucchini squash production regardless of the herbicide treatment.

Persistence of microencapsulated (ME) and emulsifiable concentrate (EC) formulations of alachlor and acetochlor, as well as EC formulations of metolachlor, s-metolachlor, dimethenamid, and flufenacet were studied using a bioassay based on root response of oat Kassandra grown in soil. Flufenacet was the most persistent of the herbicides, but biologically available residues were not detected at 0- to 10-cm soil depth 50 d after any herbicide treatment. All herbicides applied preemergence (PRE) in field trials gave good to excellent control of redroot pigweed, black nightshade, barnyardgrass, and green foxtail but only partial control of jimsonweed. Furthermore, when they were applied postemergence (POST) in mixture with atrazine in the field, the control obtained for black nightshade, common lambsquarters, common purslane, and redroot pigweed was excellent, but good to excellent for bristly foxtail and green foxtail. Their efficacy against yellow foxtail and large crabgrass was fair to good. Generally, the EC-alachlor and EC-acetochlor applied POST in mixture with atrazine gave better control of grasses than did their ME-formulations. None of the herbicide treatments showed any phytotoxic effect on corn, and all of them produced corn yield greater than that of weedy control but slightly lower than that of the weed-free control. Flufenacet, s-metolachlor, and dimethenamid were suitable alternatives to acetochlor, alachlor, and metolachlor.

Goosegrass is a problematic weed in turfgrass, and overuse of dinitroaniline (dna) herbicides has resulted in evolution of resistant populations. The objectives of this research were to (1) evaluate responses of a susceptible (S) goosegrass compared to a suspected resistant (R) biotype from Griffin, GA to prodiamine, and (2) evaluate efficacy of various PRE herbicides for control. Prodiamine rates required for 50% control and 50% shoot reductions after 6 wk for R-goosegrass measured > 13.44 and 3.2 kg ai ha−1, respectively, whereas rates for the S-population measured 0.45 and < 0.42 kg ha−1, respectively. In field experiments, sequential applications of dithiopyr and prodiamine provided < 20% control of R-goosegrass over 2 yr. Single applications of dimethenamid-P at 1.68 kg ai ha−1 provided < 50% goosegrass control in 2011 but provided excellent control (≥ 90%) at 7 mo after initial treatments (MAIT) in 2012. Single and sequential applications of indaziflam provided excellent control of goosegrass in both years, and oxadiazon controlled goosegrass > 85% at 7 MAIT in 2011 and ≥ 90% in 2012. Single and sequential PRE sulfentrazone applications controlled goosegrass < 60% in 2011 but averaged 94% control in 2012. Overall, indaziflam and oxadiazon provided good (80 to 89%) to excellent control of dna-resistant goosegrass in both years, but dimethenamid and sulfentrazone were inconsistent.

In previous research, use of PRE soil residual herbicides was reduced 50% in no-till corn and soybean by banding herbicides over crop rows followed by mowing weeds growing between rows two times. The research goals were (1) to determine whether such between-row mowing systems adequately controlled weeds and prevented grain yield loss in other competitive field crops, such as no-till grain sorghum, and (2) to compare broadcast herbicide treatments with between-row mowing systems. PRE atrazine plus dimethenamid at relative rates of 0.75× and 1× (where 1× = 1.7 plus 1.3 kg ai/ha, respectively) were band-applied over rows shortly after planting followed by two between-row mowings close to the soil surface. In 2 of 3 yr in Missouri, this system controlled giant foxtail and common waterhemp as well as broadcast herbicides in no-till sorghum. In 2 of 3 yr, between-row mowing systems also prevented yield loss in no-till sorghum as well as both broadcast herbicides at the same rates and the weed-free check.

Experiments were conducted in Lewiston, NC, in 1999 and 2000 and Rocky Mount, NC, in 1999 to evaluate weed management systems in strip- and conventional-tillage peanut. The peanut cultivars grown were ‘NC 10C’, ‘NC 12C’, and ‘NC 7’, respectively. Weed management systems consisted of different combinations of preemergence (PRE) herbicides including diclosulam and flumioxazin plus commercial postemergence (POST) herbicide systems. Dimethenamid plus diclosulam or flumioxazin PRE controlled common lambsquarters, eclipta, and prickly sida at least 91%. Diclosulam and flumioxazin provided variable control of three Ipomoea species (59 to 91%) and bentazon plus acifluorfen POST provided > 90% control. Only diclosulam systems controlled yellow nutsedge 90% late season. Annual grass control required clethodim late POST, regardless of tillage system. Dimethenamid plus diclosulam or flumioxazin PRE produced equivalent yields and net returns with no significant differences between the two PRE options. Both systems produced higher yields and net returns than dimethenamid regardless of the POST herbicide option. The tillage production system did not influence weed control of eight weeds, peanut yields, or net returns. The addition of diclosulam or flumioxazin to dimethenamid PRE improved weed control compared with dimethenamid PRE alone.

Field experiments were conducted in 2003 and 2004 to determine the tolerance of direct-seeded leafy turnip greens, mustard greens, kale, and collard to selected preemergence and postemergence herbicides and to determine the efficacy of these herbicides against weeds that are common to the southeastern coastal plains of the United States. Pendimethalin applied preemergence controlled large crabgrass, goosegrass, carpetweed, and common purslane, but it injured turnip greens, mustard greens, kale, and collard. Dimethenamid at 0.31 and 0.63 kg ai/ha controlled large crabgrass and goosegrass but did not control hairy nightshade or common purslane at the lower rate. In 2003, dimethenamid at 0.63 kg/ha injured mustard greens, kale, and collard more than 40%. S-metolachlor applied preemergence at 0.45 kg ai/ha controlled large crabgrass, goosegrass, hairy nightshade, and common purslane while causing little or no injury to turnip greens, mustard greens, kale, and collard. Clopyralid at 0.10 kg ai/ha controlled common lambsquarters 76 to 95% and hairy nightshade 93% but did not control carpetweed, common purslane, large crabgrass, and goosegrass. Turnip greens, mustard greens, kale, and collard generally were tolerant of clopyralid, but mustard was injured 29% in 2003. Phenmedipham alone or in combination with desmedipham injured mustard greens 54 to 82% in 2003 and failed to control weeds. Of the herbicides evaluated, S-metolachlor provides the best potential to improve weed control in direct-seeded leafy greens in the southeastern United States.

Field research conducted over 3 yr evaluated the utility of preemergence (PRE), soil-applied herbicides at half- and full-label rates in glyphosate-resistant soybean. Soil-applied herbicide treatments at full-label rates included pendimethalin plus imazaquin (0.84 + 0.14 kg ai/ha), pendimethalin (1.12 kg/ha), metolachlor (1.68 kg ai/ha), dimethenamid plus imazaquin (1.0 + 0.14 kg ai/ha), sulfentrazone plus chlorimuron (0.22 + 0.04 kg ai/ha), and metribuzin plus chlorimuron (0.36 + 0.06 kg ai/ha). Weed density and growth were reduced when PRE herbicides were used, and in many cases for broadleaf weeds, half-label rates were as effective as full rates. None of the herbicides provided complete control of all weeds. Sulfentrazone plus chlorimuron reduced ivyleaf morningglory density an average of 90%. For hemp sesbania, metribuzin plus chlorimuron reduced weed emergence over 3 yr at least 95%. The initial glyphosate application was made when the largest weeds, barnyardgrass or hemp sesbania, reached 10 cm. In 1998 all soil-applied herbicide treatments extended the time period of glyphosate application by 3 to 5 d when compared with the nontreated control. In 1999 the full rate of metribuzin plus chlorimuron delayed the application of glyphosate by 6 d, and an extension of 7 d was noted for the full rates of sulfentrazone or metribuzin plus chlorimuron in 2000. When soil-applied herbicides were used each year, only a single application of glyphosate was needed. A second glyphosate application was needed in only 1 yr when soil-applied herbicides were not used. Even though differences in weed control were observed among the herbicide treatments, soybean yield was the same.