Sedges are problematic weeds that reduce quality of turfgrass sod, and herbicides may be needed for control prior to harvesting. The objective of this research was to evaluate application timing of halosulfuron and sulfentrazone on sod quality, tensile strength, and postharvest rooting of four warm-season turfgrasses. Bermudagrass injury from herbicides was minimal (< 10%), but injury to centipedegrass, St. Augustinegrass, and zoysiagrass was detected before harvesting and generally increased with sulfentrazone rate from 0.21 to 0.84 kg ai ha−1. Sod tensile strength was not reduced from the nontreated for bermudagrass and centipedegrass treated with herbicides, but tensile strength was reduced 15 and 22% following herbicide applications 1 wk before harvesting (WBH) St. Augustinegrass and zoysiagrass, respectively. Sulfentrazone at 0.84 kg ha−1 reduced zoysiagrass tensile strength 20% from the nontreated, but other treatments did not reduce measurements. Turfgrass injury from halosulfuron was negligible on all species, and treatments did not affect sod tensile strength of the four species. Treatments did not affect root mass of any species at 4 wk after sod transplanting. Sod quality after transplanting was reduced from the nontreated on several dates for centipedegrass and St. Augustinegrass when treated with sulfentrazone 1 and 2 WBH, and zoysiagrass quality was reduced from treatments 4 WBH. Bermudagrass quality after transplanting was not reduced from the nontreated by any herbicides. Results suggest sod harvesting should be delayed 1, > 2, > 2, and ≥ 4 weeks after sulfentrazone applications at labeled rates for bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass, respectively. Sod harvesting should be delayed 1, 2, ≥ 4, and 2 wk after halosulfuron treatments at 0.07 kg ai ha−1 for bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass, respectively.

Seed production of annual weeds persisting through cropping phases replenishes/establishes viable seed banks from which these weeds will continue to interfere with crop production. Harvest weed seed control (HWSC) systems are now viewed as an effective means of interrupting this process by targeting mature weed seed, preventing seed bank inputs. However, the efficacy of these systems is directly related to the proportion of total seed production that the targeted weed species retains (seed retention) at crop maturity. This study determined the seed retention of the four dominant annual weeds of Australian cropping systems - annual ryegrass, wild radish, brome grass, and wild oat. Beginning at the first opportunity for wheat harvest and on a weekly basis for 28 d afterwards the proportion of total seed production retained above a 15 cm harvest cutting height was determined for these weed species present in wheat crops at nine locations across the Western Australian (WA) wheat-belt. Very high proportions of total seed production were retained at wheat crop maturity for annual ryegrass (85%), wild radish (99%), brome grass (77%), and wild oat (84%). Importantly, seed retention remained high for annual ryegrass and wild radish throughout the 28 d harvest period. At the end of this period, 63 and 79% of total seed production for annual ryegrass and wild radish respectively, was retained above harvest cutting height. However, seed retention for brome grass (41%) and wild oat (39%) was substantially lower after 28 d. High seed retention at crop maturity, as identified here, clearly indicates the potential for HWSC systems to reduce seed bank replenishment and diminish subsequent crop interference by the four most problematic species of Australian crops.

Indaziflam is a PRE herbicide for control of annual grass and broadleaf weeds in numerous settings, including managed roadsides, railroads, and noncroplands. There is a need for new and improved PRE herbicides for herbaceous vegetation management along roadsides; however, off-target crop injury via spray drift is a concern because of the close proximity of roadside applications to the wide array of crops grown throughout the southeastern United States where indaziflam is used. Greenhouse research was conducted to evaluate the effect of PRE and POST simulated indaziflam spray drift rates on the growth of cotton, bell pepper, soybean, squash, tobacco, and tomato. Simulated indaziflam spray drift rates were 100, 20, 10, 5, or 2.5% of a 73 g ai ha−1 application rate, whereas other herbicide treatments included for comparative purposes were applied at 10% of a typical North Carolina roadside vegetation management application rate. These included sulfometuron (4 g ai ha−1), aminocyclopyrachlor + metsulfuron (11 + 3.5 g ai ha−1), clopyralid + triclopyr (21 + 63 g ai ha−1), or aminopyralid (12 g ai ha−1). In general, plant growth responses varied among herbicides and application timings. Across all evaluated parameters, indaziflam at the 10% simulated drift rate adversely effected plant growth similarly or less than all other herbicides when applied PRE (squash and tomato), POST (bell pepper and soybean), and PRE or POST (cotton and tobacco). No clear trends were observed regarding indaziflam application timing, as PRE squash and tomato, and POST bell pepper and soybean applications were safer than their respective alternative timing, and no significant differences were detected between timings on cotton or tobacco. Across application timings, plant susceptibility to indaziflam-simulated spray drift rates ranked cotton < tobacco < tomato < squash < pepper < soybean. Finally, it should be noted that the lowest simulated indaziflam drift rate (2.5%) caused greater than 20% root mass reduction on cotton (POST), bell pepper (PRE and POST), soybean (PRE and POST), squash (PRE), and tomato (POST). Although this research supports indaziflam use along roadsides, it still poses an off-target plant injury risk. Future research should evaluate techniques to minimize spray drift from roadside pesticide applications.

In Australia, most wheat is sown in a no-till system without prior cultivation where herbicides are applied prior to sowing and incorporated by the planter. Trifluralin has been the most widely used PRE herbicide to control rigid ryegrass. The objective of this research was to determine crop safety and efficacy of alternative mechanism of action PRE herbicides for rigid ryegrass control in no-till wheat production. Pyroxasulfone achieved 98% control with PRE applications. The alternative PRE herbicides tested alone and in mixtures occasionally resulted in a significant reduction in wheat emergence but not crop yield. Trifluralin treatments failed at sites having trifluralin-resistant rigid ryegrass. Pyroxasulfone and prosulfocarb plus S-metolachlor were effective for control of rigid ryegrass across all trials with control ranging from 64 to 94%. This research demonstrated that PRE applications of herbicides other than trifluralin such as pyroxasulfone and prosulfocarb plus S-metolachlor can be safely and effectively used to control rigid ryegrass in no-till wheat.

Glyphosate-resistant (GR) Palmer amaranth is a widespread problem in southeastern cotton production areas. Herbicide programs to control this weed in no-till cotton commonly include flumioxazin applied with preplant burndown herbicides approximately 3 wk before planting followed by fomesafen applied PRE and then glufosinate or glyphosate applied POST. Flumioxazin and fomesafen are both protoporphyrinogen oxidase (PPO) inhibitors. Multiple yearly applications of PPO inhibitors in cotton, along with widespread use of PPO inhibitors in rotational crops, raise concerns over possible selection for PPO resistance in Palmer amaranth. An experiment was conducted to determine the potential to substitute diuron for one of the PPO inhibitors in no-till cotton. Palmer amaranth control by diuron and fomesafen applied PRE varied by location, but fomesafen was generally more effective. Control by both herbicides was inadequate when timely rainfall was not received for activation. Palmer amaranth control was more consistent when programs included a preplant residual herbicide. Applied preplant, flumioxazin was more effective than diuron. Programs with diuron preplant followed by fomesafen PRE were as effective as flumioxazin preplant followed by fomesafen only if fomesafen was activated in a timely manner. Programs with flumioxazin preplant followed by diuron PRE were as effective as flumioxazin preplant followed by fomesafen PRE at all locations, regardless of timely activation of the PRE herbicide. As opposed to flumioxazin preplant followed by fomesafen PRE, which exposes Palmer amaranth to two PPO-inhibiting herbicides, one could reduce selection pressure by using flumioxazin preplant followed by diuron PRE without sacrificing Palmer amaranth control or cotton yield.

Metamifop is an aryloxyphenoxypropionate herbicide under evaluation in the United States for annual grass control in cool-season turfgrasses. Insufficient information is available on the most effective metamifop application timings and mixtures for POST smooth crabgrass control. Field trials conducted in Blacksburg, VA, evaluated metamifop for smooth crabgrass control in existing stands of perennial ryegrass, Kentucky bluegrass, and tall fescue at three rates compared to fenoxaprop, metamifop applied twice at three application intervals, and metamifop in combination with the broadleaf herbicides carfentrazone, 2,4-D plus dicamba plus mecoprop (DDM), and mesotrione. Smooth crabgrass control was equivalent with metamifop at 400 g ai ha−1 and fenoxaprop at 195 g ai ha−1. Smooth crabgrass cover was 2% or less, 12 wk after initial treatment, when treated twice with metamifop (300 g ha−1) at a 3-, 6-, or 8-wk interval and significantly better than metamifop applied once. Smooth crabgrass cover was significantly greater at every assessment date in plots treated with metamifop plus DDM than all other metamifop plus broadleaf herbicide admixtures. Metamifop did not appear to significantly injure any turfgrass in these studies, but conclusions about metamifop safety to cool-season turfgrasses cannot be made from these studies due to nonreplication of turfgrass species. According to these data, metamifop is an effective herbicide for controlling smooth crabgrass in cool-season turfgrasses when applied once at 300 or 400 g ha−1 or twice at a 3-, 6-, or 8-wk interval. Although metamifop continues to control smooth crabgrass when added to some broadleaf herbicides, smooth crabgrass control was reduced when metamifop was combined with DDM.

Flumioxazin provides PRE and POST, annual weed control in dormant bermudagrass, but applications during active growth may be injurious. Flumioxazin could also provide an alternative chemistry for POST annual bluegrass control in other turfgrasses, but research is limited on tolerance levels. The objective of this research was to evaluate tolerance of five warm-season turfgrasses to flumioxazin applied at various rates and timings. Late-winter applications of flumioxazin at 0.21, 0.42, or 0.84 kg ai ha−1 caused acceptable (< 20%) injury to bermudagrass, seashore paspalum, St. Augustinegrass, and zoysiagrass at 3, 6, and 9 wk after treatment (WAT) in both years. In 2012, late-winter applications to centipedegrass caused unacceptable injury at 6 WAT, but turf recovered to acceptable levels by 9 WAT at all rates. Applications made during active turfgrass growth caused unacceptable initial injury to all species. However, bermudagrass, seashore paspalum, St. Augustinegrass, and zoysiagrass recovered to < 20% injury by 9 WAT from all rates. In 2012, centipedegrass treated in midspring had 0, 24, and 74% injury from flumioxazin at 0.21, 0.42, and 0.84 kg ha−1, respectively, at 9 WAT. In 2013, midspring applications to centipedegrass caused 13, 48, and 71% injury from 0.21, 0.42, and 0.84 kg ha−1, respectively at 9 WAT. Overall, flumioxazin has the potential to control annual weeds in bermudagrass, seashore paspalum, St. Augustinegrass, and zoysiagrass with late-winter applications before greenup, but all turfgrasses may be excessively injured during active growth.

Four field studies were conducted over a 3-yr period (2011 to 2013) to determine the tolerance of four soybean cultivars to pyroxasulfone (89 and 178 g ai ha−1), flumioxazin (71 and 142 g ai ha−1), and pyroxasulfone + flumioxazin (160 and 320 g ai ha−1) applied either preplant incorporated (PPI), PRE, or at the soybean cotyledon stage (COT). When pyroxasulfone + flumioxazin was applied at 160 and 320 g ai ha−1, at the cotyledon stage soybean yield was decreased by 9 and 14%, respectively. The only other treatment that decreased soybean yield was pyroxasulfone (178 g ai ha−1) applied PPI; yield was decreased by 6% despite minimal injury and dry biomass reductions observed during the season. Soybean tolerance to pyroxasulfone or flumioxazin applied alone was generally similar and injury was less than with pyroxasulfone + flumioxazin. Similarly, herbicides applied PPI and PRE were less injurious to soybean than the COT timing. Results suggest that soybean is tolerant to PPI and PRE applications of pyroxasulfone + flumioxazin but COT applications should be avoided.

Pyroxasulfone dissipation and mobility in the soil was evaluated and compared to S-metolachlor in 2009 and 2010 at two field sites in northern Colorado, on a Nunn fine clay loam, and Olney fine sandy loam soil. Pyroxasulfone dissipation half-life (DT50) values varied from 47 to 134 d, and those of S-metolachlor ranged from 39 to 63 d. Between years, herbicide DT50 values were similar under the Nunn fine clay loam soil. Under the Olney fine sandy loam soil, dissipation in 2009 was minimal under dry soil conditions. In 2010, under the Olney fine sandy loam soil, S-metolachlor and pyroxasulfone had half-lives of 39 and 47 d, respectively, but dissipation rates appeared to be influenced by movement of herbicides below 30 cm. Herbicide mobility was dependent on site-year conditions, in all site-years pyroxasulfone moved further downward in the soil profile compared to S-metolachlor.

Fresh market pepper and tomato are important crops in Florida. Production primarily occurs on raised beds covered with plastic mulch. Weeds emerging between the rows are often controlled with multiple applications of burndown and soil-residual herbicides. Crop damage attributed to root uptake of herbicides applied between the rows has been reported. An experiment was conducted in a greenhouse at the Gulf Coast Research and Education Center to examine the effect of root uptake of paraquat and paraquat tank-mixed with flumioxazin on pepper and tomato growth and yield. Herbicides were applied via subsurface irrigation at 0.0625×, 0.125×, 0.25×, 0.5×, 1×, 2×, 4×, 8×, and 16× labeled rates. The 1× rate was based on the estimated label rate that would be applied per plant in the field and was 0.122 g ai plant−1 (1,542 g ai ha−1) and 0.011 g ai plant−1 (143 g ai ha−1) for paraquat and flumioxazin, respectively. Root uptake caused necrosis of the veins, followed by complete tissue death at higher rates. The percentage of crop damage increased with herbicide rate for both species (P < 0.0001), with greater damage observed at the lower rates with the tank mix than with the paraquat alone. A reduction in shoot biomass and fruit yield of both crops was observed following root uptake. These results suggest that uptake of paraquat or paraquat tank-mixed with flumioxazin by pepper and tomato roots in a field situation is possible.

Field trials were initiated in fall 2011 to determine the potential of pyroxasulfone to control acetolactate synthase (ALS) inhibitor-resistant weeds in field pea. Pyroxasulfone was applied in split-plot trials at five locations in western Canada using fall and PRE spring applications of 0 to 400 g ai ha−1. Trial locations were chosen with a range of soil organic matter content: 2.9, 4.3, 5.5, 10.5, and 10.6% at Scott, Kernen, Kinsella, Melfort, and Ellerslie, respectively. The herbicide dose required to reduce biomass by 50% (ED50) in false cleavers ranged between 53 and 395 g ha−1 at Scott and Ellerslie, respectively. Wild oat ED50s varied between 0.54 g ha−1 at Scott in the fall and 410 g ai ha−1 in the spring at Melfort. ED50s for wild oat and false cleavers varied by 7.4- and 746-fold, respectively, depending primarily on the organic matter content at the trial location. The effect of application timing was not consistent. Significant yield reductions and pea injury occurred at 150 and 100 g ha−1 and higher at Kernen and Scott, respectively. Low organic matter and high precipitation levels at these locations indicates increased herbicide activity under these conditions. Pyroxasulfone may allow control of ALS inhibitor-resistant false cleavers and wild oat; however, locations with high soil organic matter will require higher rates than those with low organic matter for similar control levels.

Methiozolin is a new herbicide from South Korea currently under development in the United States for PRE and POST annual bluegrass control in bentgrass and most other cool- and warm-season turfgrasses. Greenhouse studies were conducted in 2012 at the University of California, Riverside, CA, and Auburn University, Auburn, AL, to evaluate the relative tolerance of three bentgrass species comprised of nine creeping bentgrass (CRBG) cultivars, velvet bentgrass (VBG) and colonial bentgrass (COBG) to methiozolin at 0, 0.6, 1.1, 2.2, 4.5 and 9.0 kg ai ha−1. Methiozolin was applied 7 wk after seeding, followed by a second application 5 wk later. Methiozolin rates that produced 25% injury (TI25) and 50% clipping dry weight reduction (GR50) relative to a nontreated control for each species or cultivar were calculated using four-parameter logistic regression. Turf injury rates at 21 d after second treatment (DAT2) were the most consistent in describing relative tolerance among bentgrass species. Overall, CRBG was more tolerant to methiozolin than VBG or COBG. After two applications, methiozolin rates that caused TI25 were 1.1, 0.2, and 0.3 kg ha−1 for CRBG (across all cultivars), VBG, and COBG, respectively. VBG and COBG were not tolerant of sequential methiozolin applications at rates necessary to control annual bluegrass under field conditions. Herbicide rates that caused TI25 and GR50 decreased with the second application. ‘Penn A-4’ CRBG exhibited the highest TI25 28 d after initial treatment (DAIT) at University of California at Riverside (4.5 kg ha−1), but only 2.5 kg ha−1 with two applications by 21 DAT2. All CRBG cultivars tested tolerated methiozolin at 0.5 kg ha−1, the recommended sequential use rate for putting greens in Korea.

Understanding the persistence of PRE-applied pendimethalin is important in determining timing of subsequent weed management programs in sugarcane on organic soils in the Everglades Agricultural Area (EAA). Dissipation of oil- and water-based pendimethalin formulations applied PRE at 2, 4, and 8 kg ai ha−1 were compared in 2011 and 2012 on organic soils in the EAA. The rate of dissipation of both formulations was very similar. Both formulations had an initial rapid rate of dissipation followed by a slower rate of dissipation. However, the initial amount of pendimethalin in the soil was higher with the water-based compared to the oil-based formulation, most likely because of the lower volatility of the water-based formulation. The half-lives (DT50s) of the oil-based formulation were 32, 18, and 10 d and 8, 8, and 12 d at 2, 4, and 8 kg ha−1, respectively, in 2011 and 2012, respectively. The DT50s of the water-based formulation were 20, 13, and 10 d and 12, 12, and 14 d at 2, 4, and 8 kg ha−1, respectively in 2011 and 2012, respectively. These DT50 values were attributed to low soil water content as well as the absence of incorporation following application. Our results suggest that dissipation of pendimethalin is rapid on organic soils irrespective of the formulation when applied under dry soil conditions with no incorporation into the soil.

Perennial grasses are expected to comprise a substantial portion of the lignocellulosic biomass to meet renewable energy mandates in the U.S. in the next decade. As many warm-season grasses are slow to establish from seed, plantings are often compromised by weed interference during the establishment year. Greenhouse experiments were conducted to determine the tolerance of switchgrass and prairie cordgrass to several herbicides applied PRE or POST (at four different growth stages). Preemergence atrazine at rates ≤ 1.684 kg ai ha−1 in switchgrass and quinclorac at rates ≤ 0.279 kg ai ha−1 in prairie cordgrass did not significantly reduce emergence, plant height, or biomass yield 8 wk after treatment. When treatments were applied at the two- to three-leaf stage, only atrazine (≤ 0.123 kg ai ha−1) did not reduce switchgrass fresh weight and only 2,4-D ester (≤ 0.533 kg ae ha−1), nicosulfuron (0.018 kg ai ha−1), and quinclorac (0.140 kg ha−1) did not significantly reduce prairie cordgrass yield. Phytotoxic effects decreased for all herbicides with increasing growth stage at the time of treatment for both species. All evaluated herbicides were safe with respect to biomass yield on the respective grasses when applied at the latest growth stage (approximately five-leaf stage). These results show that viable PRE and POST herbicides are available for weed control during establishment of switchgrass and prairie cordgrass; however, all evaluated herbicides would likely reduce biomass yield in a mixture planting of both grasses.

A sulfonylurea (SU) herbicide resistance allele discovered in prickly lettuce was previously transferred to domestic lettuce with the cultivar name ‘ID-BR1’. ID-BR1 was acquired, and the SU resistance allele was transferred through traditional breeding methods to five common commercial lettuce types: butterhead, crisphead, green leaf, red leaf, and romaine. Field trials were conducted at Salinas, CA during 2011 and 2012 to evaluate POST applications of tribenuron-methyl (tribenuron) on SU-susceptible and SU-resistant lettuce types. Treatments included a nontreated control, pronamide applied PRE at 1,340 g ai ha−1, and tribenuron at 4, 9, and 17 g ai ha−1 applied POST. Data collected were: weed control, crop injury estimates (0 = safe, 100 = dead), stand counts, and lettuce yields. Injury to lettuce from tribenuron was high in SU-susceptible lettuce types and low in SU-resistant accessions. With the exceptions of a romaine lettuce line that still may have some susceptible individuals, tribenuron did not reduce yield of SU-resistant lettuce, but did reduce the yield of SU-susceptible lettuce. Suppression of weeds such as common groundsel and annual sowthistle was higher with tribenuron than with pronamide. Tribenuron should be considered for registration as a lettuce herbicide for SU-resistant lettuce to improve current weed management options for that crop.

Dense populations of glyphosate-resistant (GR) Italian ryegrass are problematic for spring burndown herbicide programs and crop establishment in the midsouthern United States. Two field studies were conducted to evaluate fall-applied residual herbicides for control of GR Italian ryegrass and to identify the most effective application timing for these herbicides. Fall applications of clomazone at 0.84 and 1.12 kg ai ha−1, pyroxasulfone at 0.16 kg ai ha−1, and S-metolachlor at 1.79 kg ai ha−1 controlled GR Italian ryegrass ≥ 93% 180 d after application. Control from incorporated applications of pendimethalin at 1.59 kg ai ha−1 and trifluralin at 1.68 kg ai ha−1 and surface applications of S-metolachlor at 1.42 kg ha−1 provided control similar to the best treatments. Glyphosate-resistant Italian ryegrass control following clomazone, pyroxasulfone, S-metolachlor, or trifluralin applied in mid September, October, or November exceeded that from fall tillage by 19 to 56% at 90 and 140 d after the last treatment. Pyroxasulfone and S-metolachlor controlled more GR Italian ryegrass following October or November applications compared with those in September at both 90 and 140 d after the last application timing. However, the benefit of delaying clomazone application from October to November was not realized until the last evaluation (140 d after the last treatment). Clomazone, pyroxasulfone, and S-metolachlor offer growers the best opportunity for residual control of GR Italian ryegrass, and control is optimized when these herbicides are applied in November.

American burnweed is an early successional summer annual species in the Asteraceae. This weed is a poor competitor; however, it rapidly colonizes disturbed and low-maintenance areas, especially following an environmental disturbance. Recently, turfgrass managers have made adjustments to maintenance practices to satisfy budget requirements and address environmental concerns. This has resulted in reduced mowing frequency in some golf course rough and out-of-play turf areas, and has allowed establishment of broadleaf weed species such as American burnweed which would otherwise be controlled by frequent mowing. The purpose of this study was to evaluate PRE and POST herbicide treatments for American burnweed control in an unmown bermudagrass golf course rough. Single PRE applications of simazine at 2.24 kg ai ha−1 and indaziflam at 0.06 kg ai ha−1 provided > 80% American burnweed control 24 wk after treatment (WAT) in 2012 and 2013. Sequential combination applications of liquid formulations of dimethenamid-p + pendimethalin (2.24 + 1.68 kg ai ha−1) provided 95% American burnweed control 24 wk after initial treatment in 2012 and 2013. Other PRE treatments did not provide consistent control of American burnweed across rating dates and years. Regardless of year, four POST treatments provided ≥ 87% control at 8 and 16 WAT. These included thiencarbazone + foramsulfuron + halosulfuron (0.02 + 0.044 + 0.07 kg ai ha−1), thiencarbazone + iodosulfuron + dicamba (0.02 + 0.15 + 0.005 kg ai ha−1), triclopyr + clopyralid (0.88 + 0.32 kg ai ha−1), and sulfentrazone + metsulfuron (0.4 + 0.04 kg ai ha−1). Several PRE and POST American burnweed control solutions exist for low maintenance bermudagrass areas. Future research should continue to screen other herbicides for control efficacy and focus on application timing to balance season-long control with minimal chemical inputs.

Herbicide-resistant barnyardgrass has become widespread in the rice production systems of the midsouthern United States, leaving few effective herbicide options for controlling this weed. The acetolactate synthase (ALS)- and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides remain largely effective in Clearfield® rice production, but strategies need to be developed to protect the long-term utility of these options. A two-trait model was developed to understand simultaneous evolution of resistance in barnyardgrass to the ALS- and ACCase-inhibiting herbicides in Clearfield rice. The model was used to predict resistance under a number of common weed management scenarios across 1,000 hypothetical rice fields in the Mississippi Delta region and answer some key management questions. Under an ALS inhibitor–only program consisting of three annual applications of imidazolinone herbicides (imazethapyr or imazamox) in continuous Clearfield rice, resistance was predicted within 4 yr with 80% risk by year 30. Weed management programs that consisted of ALS- and ACCase-inhibiting herbicides such as fenoxaprop and cyhalofop greatly reduced the risk of ALS-inhibiting herbicide resistance (12% risk by year 30), but there was a considerable risk for ACCase resistance (evolving by year 14 with 13% risk by year 30) and multiple resistance (evolving by year 16 with 11% risk by year 30) to both of these mechanisms of action. A unique insight was that failure to stop using a herbicide soon after resistance evolution can accelerate resistance to the subsequent herbicide option. Further, a strong emphasis on minimizing seedbank size is vital for any successful weed management strategy. Results also demonstrated that diversifying management options is not just adequate, but diversity combined with timely herbicide applications aimed at achieving high efficacy levels possible is imperative.

Fomesafen and imazosulfuron are two recently registered herbicides for use in Florida bell pepper. Field studies were conducted in 2012 and 2013 to evaluate PRE, POST-directed (POST-DIR), and PRE followed by (fb) POST-DIR control programs utilizing these new herbicides for nutsedge control in Florida bell pepper. PRE treatments included: S-metolachlor at 0.71 and 1.07 kg ai ha−1, fomesafen at 0.28 and 0.42 kg ai ha−1, S-metolachlor at 0.71 kg ha−1 + fomesafen 0.28 kg ha−1, and S-metolachlor at 1.07 kg ha−1 + fomesafen at 0.42 kg ha−1. POST-DIR treatments included imazosulfuron at 0.21 and 0.34 kg ai ha−1. PRE fb POST-DIR treatments included S-metolachlor at 0.71 or 1.07 kg ha−1 fb imazosulfuron at 0.21 kg ha−1 and fomesafen at 0.28 or 0.42 kg ha−1 fb imazosulfuron at 0.21 kg ha−1. Nutsedge control in both years at 28 d after planting was similar among all PRE treatments providing ≤ 60% control. The addition of imazosulfuron POST-DIR following S-metolachlor or fomesafen PRE provided greater control compared to S-metolachlor or fomesafen alone 14, 21, and 28 d after the POST-DIR application. Plots treated with S-metolachlor resulted in lower marketable weight and marketable fruit count compared to fomesafen in 2012; however, this was not observed in 2013. The results for these studies indicate the importance of a PRE fb POST-DIR herbicide for nutsedge control and that fomesafen or S-metolachlor PRE fb imazosulfuron POST-DIR provides growers with a viable tool capable of achieving season-long control of nutsedge in bell pepper.

Teff is a warm-season C4 annual grass crop grown for forage and food grain that has recently increased in production in parts of the United States. Hay from teff is well suited for livestock, especially horses. The objective of this study was to evaluate teff and weed response to selected herbicides in field studies conducted at the Malheur Experiment Station, Ontario, OR in 2009 and 2010. Herbicides were applied POST when teff was at the four-leaf stage. Broadleaf weed control at 21 d after treatment was greater than 91% across herbicide treatments. Only the premix of 2.5 g ai ha−1 florasulam + 99 g ae ha−1 fluroxypyr + 15 g ai ha−1 pyroxsulam provided acceptable control of barnyardgrass. Due primarily to barnyardgrass competition, teff treated with a premix of 2.5 g ha−1 florasulam + 99 g ha−1 fluroxypyr + 15 g ha−1 pyroxsulam produced 7,200 kg ha−1 of teff hay compared with 4,800 kg ha−1 of teff hay for 2,4-D and dicamba and 4,200 kg ha−1 teff hay when no herbicides were used. Teff grain production was greater with 2.5 g ha−1 florasulam + 99 g ha−1 fluroxypyr + 15 g ha−1 pyroxsulam compared with any of the other treatments. The use of a premix of florasulam + fluroxypyr + pyroxsulam would improve broadleaf and grass weed control in ‘Tiffany' and ‘Dessie' teff varieties, improve hay and grain yield, and reduce production costs.