Weeds are the major biotic constraint to rice production. Field observations have suggested that certain fertilizer regimes could enhance infestations of particular weed species emerging with rice. The study objective was to determine the effect of surface-applied calcium phosphate on weed growth in flooded California rice systems. In field and pot studies, triple superphosphate (TSP) applied to the soil surface increased weed emergence. Surface-applied TSP increased the number of sedge and broadleaf weeds, including smallflower umbrella sedge, blue-flowered ducksalad, redstem, ricefield bulrush, waterhyssop, and California arrowhead. A laboratory study measured germination of smallflower umbrella sedge and ricefield bulrush in response to the application of phosphorus (P) and calcium (Ca), which comprise 20 and 15% of TSP, respectively. Calcium stimulated smallflower umbrella sedge germination and had no effect on ricefield bulrush germination. Phosphorus did not stimulate either smallflower umbrella sedge or ricefield bulrush germination. Results indicate that surface applications of calcium phosphate increase the growth of certain weed species and that Ca may stimulate germination of smallflower umbrella sedge. By incorporating preplant applications of calcium phosphate into the soil profile, growers can reduce weed pressure from certain species. Alternatively, surface applications of calcium phosphate may be useful to stimulate weed emergence in stale-seedbed management.

Field studies were conducted in Powell, WY in 2006 and 2007 to determine the influence of season-long interference of various wild buckwheat densities and duration of interference on sugarbeet. Percent sucrose content was not affected by wild buckwheat interference. Root and sucrose yield loss per hectare increased as wild buckwheat density increased. The estimated percent yield loss as wild buckwheat density approaches infinity was 64 and 61% for root and sucrose yield loss, respectively. The estimated percent yield loss per unit weed density at low weed densities was 6% for both root and sucrose yield loss. Greater durations of wild buckwheat interference had a negative effect on sugarbeet root yield. The critical timing of weed removal (CTWR) to avoid 5 and 10% root yield loss was 32 and 48 d after sugarbeet emergence (DAE), respectively. These results show that wild buckwheat is competitive with sugarbeet and should be managed appropriately to forestall any negative effects on sugarbeet root and sucrose yield.

Yellow nutsedge is a problematic weed in plasticulture strawberry because herbicides and fumigants currently used in California provide little to no control and because nutsedge shoots easily penetrate standard low-density polyethylene (LDPE) mulch to rapidly establish and compete with the crop. Field studies were conducted at two California locations near Oxnard and Camarillo from 2007 to 2009 to evaluate yellow nutsedge control with physical barriers. Nutsedge germinated in both autumn and spring through LDPE mulch alone, but paper placed between two layers of standard 0.15-mm black LDPE mulch, weed barrier fabric commonly used in landscapes placed under LDPE mulch, and Tyvek Home Wrap placed under LDPE mulch suppressed nutsedge emergence. In 1 yr, the size of strawberry plants grown with weed barrier fabric was reduced 23% compared with the other treatments and the number of marketable fruit in the third month of harvest was reduced 20% compared with LDPE mulch alone, likely because inadequately cut planting holes in this barrier restricted plant growth. Estimated costs for barrier treatments ranged from $5,000 to $12,000 ha−1 compared with estimated hand-weeding costs of up to $24,000 ha−1. In 2007 to 2008 barrier treatments reduced the number of wind-dispersed weeds that commonly land and germinate in strawberry planting holes 67% compared with LDPE mulch alone. Removing the barriers at the end of the two seasons revealed that nutsedge plants sprouted but failed to grow and produce new tubers under the barriers. This observation suggests that nutsedge-impermeable barriers may aid in depletion of the soil tuber bank and therefore can be an effective tool in managing nutsedge for the length of the growing season.

Weed management systems used by sweet corn growers, including the role of atrazine, are poorly characterized. Management records of 175 fields throughout the major sweet corn production areas of the Midwest were surveyed from 2005 to 2007. Seventy-four percent of sweet corn fields in the Midwest were grown in rotation with soybean or corn. Interrow cultivation was used on 48% of fields, and atrazine use was higher in those fields without interrow cultivation. A majority of fields (54%) received both PRE and POST herbicide applications. Mesotrione was applied below the registered use rate in two-thirds of the fields in which it was used POST. Atrazine rates in sweet corn were highest when the preceding crops were other vegetables, compared to preceding crops of soybean or corn. Selective herbicides are used extensively in U.S. sweet corn production, accounting for 94% of total weed management expenditures which average $123/ha. Growers treated 66% of fields with one or more applications of atrazine at an average total use rate of 1.35 kg ai/ha. The estimated annual net cost to replace atrazine in U.S. sweet corn production with the broad spectrum broadleaf herbicide, mesotrione, is $9.2 million.

Italian ryegrass resistance to diclofop has been documented in several countries, including the United States. The purpose of this research was to screen selected putative resistant populations of Italian ryegrass for resistance to the acetyl-CoA carboxylase (ACCase)–inhibiting herbicides diclofop and pinoxaden and the acetolactate synthase (ALS)–inhibiting herbicides imazamox, pyroxsulam, and mesosulfuron in the greenhouse and to use field experiments to develop herbicide programs for Italian ryegrass control. Resistance to diclofop was confirmed in eight populations from Tennessee. These eight populations did not show cross-resistance to pinoxaden. One additional population (R1) from Union County, North Carolina, was found to be resistant to both diclofop and pinoxaden. The level of resistance to pinoxaden of the R1 population was 15 times that of the susceptible population. No resistance was confirmed to any of the ALS-inhibiting herbicides examined in this research. Field experiments demonstrated PRE Italian ryegrass control with chlorsulfuron (71 to 94%) and flufenacet + metribuzin (84 to 96%). Italian ryegrass control with pendimethalin applied PRE or delayed preemergence (DPRE) was variable (0 to 85%). POST control of Italian ryegrass was acceptable with pinoxaden, mesosulfuron, flufenacet + metribuzin, and chlorsulfuron + flucarbazone (> 80%). Application timing and herbicide treatment had no effect on wheat yield, except for diclofop and pendimethalin treatments, in which uncontrolled Italian ryegrass reduced wheat yield.

Information on chemical weed control in lily bulb production in South America is scarce. Greenhouse and field studies were conducted to evaluate the phytotoxic effect and weed control of herbicides applied PRE and POST in lily bulb production in Argentina. In greenhouse studies, bromoxynil, 415 g ai ha−1; fluroxypyr, 200 g ai ha−1; metsulfuron, 3 g ai ha−1; iodosulfuron-methyl-sodium, 3 g ai ha−1 + metsulfuron, 3 g ai ha−1; oxyfluorfen, 240 g ai ha−1; ioxynil, 529 g ai ha−1; and linuron, 750 g ai ha−1, produced severe phytotoxicity or death of bulbs. Glyphosate at 720 g ai ha−1 and aclonifen at 720 g ai ha−1 produced little to no symptoms and were considered safe to apply to lilies. In field conditions, PRE herbicides metolachlor, 960 g ai ha−1 + atrazine, 1,500 g ai ha−1, and metolachlor, 960 g ai ha−1 + flumetsulam, 80 g ai ha−1, provided good weed control but were phytotoxic for lily plants, with chlorosis as the main symptom. Metolachlor plus linuron resulted in little or no symptoms of injury and no reduction in bulb yield. Diuron, 800 g ai ha−1 POST was the most effective treatment without phytotoxicity, and, in combination with metolachlor, 960 g ai ha−1 + linuron, 750 g ai ha−1 PRE, controlled weeds until 40 d after diuron application without yield reduction. Results obtained with glyphosate indicate that the Lilium genus presents some tolerance to this herbicide, which justifies further evaluation for weed control in lily bulb production.

Seeds of a suspected glyphosate-resistant giant ragweed biotype from Lauderdale County, TN, were collected from a continuous cotton field in fall 2007 after plants were nonresponsive to multiple glyphosate applications. The objectives of this research were to (1) confirm resistance by quantifying the response of the putative resistant biotype to glyphosate compared to a susceptible biotype from a nonagricultural area, (2) quantify shikimate accumulation over time in both biotypes, and (3) determine the effectiveness of POST-applied herbicides labeled for use in cotton in controlling both biotypes at three growth stages. The susceptible biotype had a 50% lethal dose of 407 g ae/ha of glyphosate compared with 2,176 g/ha for the resistant biotype when treated at the four-node stage, a 5.3-fold level of resistance. The resistant biotype accumulated 3.3- to 9.8-fold less shikimate than the susceptible biotype at 1 to 7 d after treatment. The resistant biotype was less responsive to glyphosate as treatment was delayed past the two-node stage, much more than the susceptible biotype. Glufosinate, MSMA, and diuron controlled both biotypes by at least 90%, regardless of size at application. Prometryn, flumioxazin, carfentrazone-ethyl, fomesafen, and trifloxysulfuron controlled both biotypes by at least 89% when applied at the two-node stage, but control generally diminished with later application timings. Pyrithiobac was not effective in controlling either biotype, regardless of size at application. Hence, there are effective herbicide options for controlling glyphosate-resistant giant ragweed in cotton, and the resistant biotype does not appear to exhibit multiple resistances to other herbicides.

There is little information on the tolerance of leguminous crops to saflufenacil. A field study was conducted three times over a 2-yr period (2006, 2007) in Ontario, Canada, to determine the tolerance of adzuki bean, cranberry bean, lima bean, processing pea, snap bean, soybean, and white (navy) bean to saflufenacil applied PRE at 100 and 200 g ai/ha. Saflufenacil caused 51 to 99% injury, reduced height 25 to 93%, reduced shoot dry weight 92 to 99%, and reduced seed yield 56 to 99% in adzuki bean, cranberry bean, lima bean, snap bean, and white bean. Injury was lower in soybean and processing pea. Saflufenacil caused 1 to 25% injury, reduced height 3 to 13%, reduced shoot dry weight 5 to 30%, and reduced seed yield 0 to 4% in soybean and processing pea. Cranberry bean, snap bean, white bean, and lima bean were the most sensitive crops to saflufenacil followed by adzuki bean. Soybean and processing pea were the most tolerant to saflufenacil. Based on these results, saflufenacil applied PRE can be safely used in specific cultivars of pea and soybean at the proposed rate of 100 g/ha. However, there is not an acceptable margin of crop safety for saflufenacil PRE at 100 or 200 g/ha in adzuki, cranberry, lima, snap, and white bean.

Greenhouse experiments were conducted to evaluate pumpkin cultivar injury and control of three grass species from tank-mixtures of halosulfuron with either clethodim or sethoxydim in combination with nonionic surfactant (NIS), crop-oil concentrate (COC), methylated seed oil (MSO), and high-surfactant oil concentrate (HSOC). Pumpkin injury, in the form of chlorosis and visual growth reduction, was 13 to 21% by 7 d after treatment (DAT) for all pumpkin cultivars. The specific adjuvant used with halosulfuron did not influence pumpkin injury or final plant dry weight. Pumpkin growth reduction at 21 DAT from halosulfuron was less than 9% for all pumpkin cultivars with the least growth reduction (5% or less) observed with Cucurbita pepo ‘Howden’, C. pepo ‘Appalachian’, and Cucurbita moschata ‘Libby's Select’. The efficacy of sethoxydim or clethodim on large crabgrass was antagonized by the addition of halosulfuron with NIS or COC. However, only combinations of sethoxydim and halosulfuron with COC or MSO were antagonistic on smooth crabgrass. Giant foxtail dry weight reduction was decreased 4 to 24% by the addition of halosulfuron to sethoxydim with NIS and clethodim regardless of adjuvant. Although the frequency and magnitude of grass antagonism was variable, the use of clethodim and MSO with halosulfuron most often provided the greatest level of grass control compared with sethoxydim or other adjuvants.

Aryloxyphenoxypropionate (AOPP) herbicides are used to control bermudagrass contamination in various turfgrasses. Applying AOPP herbicides alone can cause unacceptable injury to zoysiagrass but injury can be reduced when tank-mixed with triclopyr. There are limited data illustrating the extent of bermudagrass control and zoysiagrass cultivar tolerance when these compounds are combined. Research was conducted to determine the efficacy of multiple AOPP herbicides applied alone and tank-mixed with triclopyr for bermudagrass control in zoysiagrass turf. Treatments include three sequential applications of cyhalofop (0.32 kg ai ha−1), fenoxaprop (0.14 kg ha−1), fluazifop (0.11 kg ha−1), or quizalofop (0.09 kg ha−1) applied alone and tank-mixed with triclopyr (1.12 kg ae ha−1) applied to ‘Tifway’ bermudagrass, and ‘Diamond’, ‘Palisades’, and ‘Zenith’ zoysiagrass. Tifway bermudagrass control ranged from 41 to 69% and digital image analysis turf coverage data ranged from 18 to 50% for AOPP herbicides applied alone. The addition of triclopyr to AOPP herbicides increased bermudagrass control (64–79%) and reduced turf coverage (8–29%). Palisades and Zenith zoysiagrass exhibited less injury (1–18%) and greater turf coverage (84–86%) when AOPP herbicides were tank-mixed with triclopyr compared to AOPP herbicides applied alone. Diamond zoysiagrass was not tolerant to any AOPP herbicides applied alone or tank-mixed with triclopyr, except for fluazifop alone (18% injury and 93% turf coverage). Visual ratings and digital image analysis turf coverage data had a strong negative correlation over all tested turfgrasses. In general, AOPP herbicides plus triclopyr will control bermudagrass greater and injure zoysiagrass less compared to AOPP herbicides applied alone; however, these mixtures can cause unacceptable injury to Diamond zoysiagrass.

Field studies compared the grain yield of four two-row spring barley cultivars at four sites when sown at two-row spacing in competition with two densities of rigid ryegrass. The sites chosen had low background populations of rigid ryegrass. Although the four cultivars sown differed in their grain yield, row spacing did not influence cultivar performance. Doubling the row spacing decreased barley grain yield at three of the four sites. The impact of row spacing on grain yield was more noticeable when doubled to 48 or 50 cm compared with 36 cm. Rigid ryegrass competition reduced barley grain yield at two of the four sites. At both locations the influence of weed competition on barley grain yield was the same at both narrow and wide row spacing and at one location the impact of weed competition was modified by cultivar. Planting barley in wide rows was found to favor rigid ryegrass production through an increase in both rigid ryegrass biomass production and tiller number. The development of farming systems for barley on the basis of a row spacing greater than 25 cm is likely to be associated with an increase in weed productivity unless good integrated weed management principles are implemented. Modifications to the current system may allow an increase in row spacing without any yield loss or increased weed seed set.

Organic soil amendments are known to affect the composition and density of annual weed communities. The objective of this research was to measure the effect on emergence and growth of redroot pigweed seedlings when soil was amended with composted dairy manure at 18, 36, and 54 T/ha, or with raw dairy manure at 41, 82, and 123 T/ha. Data recorded (1) seedling emergence over 12 days, (2) number of leaves and total leaf area, (3) shoot and root dry weight, and (4) seed number. Maximum seedling emergence (32%) occurred in nonamended soil (the control). Emergence declined in a linear fashion when soil was amended with manure or with compost. Compost additions affected seedling emergence more severely than did manure additions. For every measure of redroot pigweed growth except seed production, amendment with manure at 123 T/ha retarded growth compared to soil alone or compost-amended mixes. Manure applied at 82 T/ha reduced leaf area and plant height relative to other treatments. Growth of redroot pigweed in soil amended with compost at 36 and 54 T/ha was always equal to or greater than growth in soil that was not amended. Seed production in one of two runs of the experiment was more than double in soils amended with compost at 36 and 54 T/ha compared to the nonamended soil. These results suggest that amending soils with raw dairy manure may decrease the competitiveness of redroot pigweed, whereas amending with composted manure is likely to increase competitiveness.

Studies were conducted in 2007 and 2008 to determine the effect of flumioxazin and S-metolachlor on Palmer amaranth control and ‘Beauregard’ and ‘Covington’ sweetpotato. Flumioxazin at 0, 91, or 109 g ai ha−1 was applied pretransplant 2 d before transplanting alone or followed by (fb) S-metolachlor at 0, 0.8, 1.1, or 1.3 kg ai ha−1 PRE applied immediately after transplanting or 2 wk after transplanting (WAP). Flumioxazin fb S-metolachlor immediately after transplanting provided greater than 90% season-long Palmer amaranth control. S-metolachlor applied alone immediately after transplanting provided 80 to 93% and 92 to 96% control in 2007 and 2008, respectively. Flumioxazin fb S-metolachlor 2 WAP provided greater than 90% control in 2007 but variable control (38 to 79%) in 2008. S-metolachlor applied alone 2 WAP did not provide acceptable Palmer amaranth control. Control was similar for all rates of S-metolachlor (0.8, 1.1, and 1.3 kg ha−1). In 2008, greater Palmer amaranth control was observed with flumioxazin at 109 g ha−1 than with 91 g ha−1. Sweetpotato crop injury due to treatment was minimal (< 3%), and sweetpotato storage root length to width ratio was similar for all treatments in 2007 (2.5 for Beauregard) and 2008 (2.4 and 1.9 for Beauregard and Covington, respectively). Sweetpotato yield was directly related to Palmer amaranth control. Results indicate that flumioxazin pretransplant fb S-metolachlor after transplanting provides an effective herbicide program for control of Palmer amaranth in sweetpotato.

Propane flaming could be an effective alternative tool for weed control in organic cropping systems. However, response of major weeds to broadcast flaming must be determined to optimize its proper use. Therefore, field experiments were conducted at the Haskell Agricultural Laboratory, Concord, NE in 2007 and 2008 using six propane doses and four weed species, including green foxtail, yellow foxtail, redroot pigweed, and common waterhemp. Our objective was to describe dose–response curves for weed control with propane. Propane flaming response was evaluated at three different growth stages for each weed species. The propane doses were 0, 12, 31, 50, 68, and 87 kg ha−1. Flaming treatments were applied utilizing a custom-built flamer mounted on a four-wheeler (all-terrain vehicle) moving at a constant speed of 6.4 km h−1. The response of the weed species to propane flaming was evaluated in terms of visual ratings of weed control and dry matter recorded at 14 d after treatment. Weed species response to propane doses were described by log-logistic models relating propane dose to visual ratings or plant dry matter. Overall, response of the weed species to propane flaming varied among species, growth stages, and propane dose. In general, foxtail species were more tolerant than pigweed species. For example, about 85 and 86 kg ha−1 were the calculated doses needed for 90% dry matter reduction in five-leaf green foxtail and four-leaf yellow foxtail compared with significantly lower doses of 68 and 46 kg ha−1 of propane for five-leaf redroot pigweed and common waterhemp, respectively. About 90% dry matter reduction in pigweed species was achieved with propane dose ranging from 40 to 80 kg ha−1, depending on the growth stage when flaming was conducted. A similar dose of 40 to 60 kg ha−1 provided 80% reduction in dry matter for both foxtail species when flaming was done at their vegetative growth stage. However, none of the doses we tested could provide 90% dry matter reduction in foxtail species at flowering stage. It is important to note that foxtail species started regrowing 2 to 3 wk after flaming. Broadcast flaming has potential for control or suppression of weeds in organic farming.

Field experiments were conducted at Oakes, Absaraka, and Tappen, ND, in 2006 and repeated at Oakes and Absaraka, ND, in 2007 to evaluate early season weed control of common lambsquarters and redroot pigweed in onion with POST herbicides applied at multiple reduced rates (microrates) and to determine whether microrate herbicide treatments effectively reduced early season broadleaf weed competition, caused crop injury, or affected yield. Application rates of bromoxynil, oxyfluorfen, metribuzin, and acifluorfen were reduced to 0.25, 0.13, and 0.06× of their lowest labeled rate and applied in sequential applications (every 7 d) either two or three times. The 0.25× rate of bromoxynil (70.1 g ae/ha) provided the greatest control of common lambsquarters (95%). The 0.25× rates of bromoxynil and oxyfluorfen (70.1 g ai/ha) provided the greatest control of redroot pigweed (93 and 85%, respectively). Microrate applications of metribuzin or acifluorfen did not effectively control common lambsquarters or redroot pigweed. In 2006, no onion injury was observed. However, in 2007, applications of oxyfluorfen resulted in approximately 15% injury, regardless of the herbicide rate or the number of applications. Plants outgrew symptoms by 4 wk after treatment and were similar to the untreated plants. Onion treated with oxyfluorfen had the greatest total yield, followed by onion treated with bromoxynil. Onion treated with acifluorfen had a greater total marketable bulb yield than onion treated with metribuzin, but yield was considered poor compared to the other herbicide treatments. Three microrate applications provided greater weed control and increased yield compared with two applications across herbicides and rates. Results suggest that microrate applications of bromoxynil and oxyfluorfen will provide early season broadleaf weed control in onion.

Field studies were conducted in 2006 and 2007 to evaluate the tolerance of autumn-planted cabbage and turnip green to halosulfuron applied the previous spring to cantaloupe. Main plots were three levels of soil pH: maintained at a natural pH level, pH raised with Ca(OH)2, and pH lowered with Al2(SO4)3. Subplots were a factorial arrangement of two halosulfuron application methods and three halosulfuron rates. Halosulfuron application methods were PPI or POST after transplanting to the edges of mulch-covered seedbeds. Halosulfuron rates were 35 and 70 g ai/ha, along with a nontreated control. Cantaloupe were transplanted, maintained weed-free, and evaluated for yield response. After cantaloupe harvest, direct-seeded turnip green and transplanted cabbage were established in September of each year and evaluated for crop tolerance and yield. Data indicated nonsignificant main effects of soil pH and halosulfuron application method on cantaloupe yield. However, in 2007 cantaloupe yields were significantly reduced, by 16 and 20% for halosulfuron applied at 35 and 70 g/ha, respectively. For all turnip green and cabbage response parameters, interactions were nonsignificant between application method and rate, soil pH and rate, and soil pH and application method, along with the three-way interaction. After 6 mo, there was no evidence of stunting from halosulfuron carryover in 2006 to direct-seeded turnip green and in both years to transplanted cabbage. Visual estimates of stunting to direct-seeded turnip green ranged from 9 to 16% for halosulfuron at 35 and 70 g/ha, respectively, in 2007, but all stunting was transient and turnip green yield was not affected.

Bispyribac-sodium selectively controls annual bluegrass in cool-season turf but efficacy may be influenced by management practices, such as plant growth regulator use. Experiments were conducted in New Jersey to investigate efficacy and absorption of bispyribac-sodium applied with trinexapac-ethyl for annual bluegrass control and turfgrass tolerance. In laboratory experiments with annual bluegrass, creeping bentgrass, and perennial ryegrass, tank-mixing trinexapac-ethyl with 14C-bispyribac-sodium increased presumed foliar absorption of 14C-bispyribac-sodium compared with nontrinexapac-ethyl treated; absorption increased with trinexapac-ethyl rate. Differences in 14C-bispyribac-sodium absorption were not detected among emulsifiable concentration, microencapsulated concentration, and wettable powder trinexapac-ethyl formulations. In field experiments, sequential bispyribac-sodium applications controlled annual bluegrass 93%, but trinexapac-ethyl did not affect efficacy. Tank-mixing all trinexapac-ethyl formulations with bispyribac-sodium provided similar annual bluegrass control and creeping bentgrass quality compared with bispyribac-sodium alone. Applications of bispyribac-sodium reduced dollar spot cover in both years, whereas trinexapac-ethyl reduced dollar spot cover only in 2005.

Both prodiamine and flumioxazin are used in the nursery production and landscape maintenance industries in the southeastern United States for preemergence weed control. Research was conducted to determine whether a tank mixture of these two herbicides would be more effective than either component applied alone. Prodiamine alone, flumioxazin alone, and a 72 : 28 (by weight) prodiamine–flumioxazin mixture were each applied at a series of rates to containers filled with a pine bark–sand substrate that is typical for nursery production in the southeastern United States. Our intent was to have a rate range that hopefully extended from ineffective to lethal for each treatment series. Subsequent to treatment, containers were overseeded with either large crabgrass, spotted spurge, or eclipta. Percent control was determined by comparing treated weed foliage fresh weight to that of the appropriate nontreated control at 6 and 12 wk after application. ANOVA followed by nonlinear regression was used to evaluate the interaction of prodiamine and flumioxazin when combined and to determine the rate of each treatment series required for 95% control (if applicable) for each of the three weed species. Results varied with weed species. The mixture was synergistic and more cost effective than either of the components applied alone in controlling spotted spurge. With respect to large crabgrass control, the mixture was additive and slightly more cost effective than the components. Eclipta could only be controlled with flumioxazin, and this control was antagonized by the addition of prodiamine.

Bispyribac-sodium effectively controls annual bluegrass in creeping bentgrass fairways but efficacy on putting greens may be affected by management differences and thus, application regimes may need to be modified for effective annual bluegrass control. To test this hypothesis, field experiments investigated various bispyribac-sodium application regimens for annual bluegrass control on creeping bentgrass putting greens. Bispyribac-sodium regimes totaling 148, 222, and 296 g ha−1 controlled annual bluegrass 81, 83, and 91%, respectively, over 2 yr. Pooled over herbicide rates, bispyribac-sodium applied two, three, and six times controlled annual bluegrass 78, 83, and 94%, respectively. The most effective bispyribac-sodium regime was 24.6 g ha−1 applied weekly, which controlled annual bluegrass 90% after 8 wk with acceptable levels of creeping bentgrass discoloration. After 8 wk, all regimes reduced turf quality as a result of voids in turf following annual bluegrass control; regimes with six applications reduced turf quality the most.