Growth chamber experiments were conducted in the fall of 2006 and spring of 2007 to determine winter wheat, flixweed, and henbit response to POST treatments of saflufenacil at 13, 25, and 50 g ai ha−1 applied alone and in combinations with bentazon at 560 g ai ha−1 or 2,4-D amine at 533 g ae ha−1 and nonionic surfactant (NIS) at 0.25% v/v. Mixtures of saflufenacil and 2,4-D amine were also applied without NIS. Necrosis was observed on wheat leaves within 1 d after treatment (DAT) and peaked at 5 to 7 DAT. Saflufenacil at 13, 25, or 50 g ai ha−1 applied alone or in combination with 533 g ae ha−1 of 2,4-D amine plus NIS caused 19 to 38% (alone) and 24 to 40% (in combination) wheat foliar necrosis, respectively. Foliar necrosis of wheat was 14% or less when saflufenacil, at any rate, was mixed with bentazon or 2,4-D amine without NIS. Combinations of saflufenacil at any of the rates tested plus bentazon and NIS did not reduce wheat dry weight. Saflufenacil plus 2,4-D amine without adjuvant resulted in similar wheat dry weights as 2,4-D amine. Saflufenacil plus 2,4-D amine without NIS provided 99% control of flixweed at 21 DAT, but henbit control ranged from 81 to 88%. In comparison, saflufenacil at 50 g ha−1 mixed with bentazon and NIS controlled flixweed at 92% and henbit at 63% at 21 DAT. This research indicates saflufenacil has potential for POST use in winter wheat to control winter annual broadleaf weeds when tank-mixed with 2,4-D amine without NIS, but additional research is needed to discover ways to improve crop safety without reducing weed control.

Oriental mustard seed meal (MSM), a byproduct generated by pressing the seed for oil, exhibits herbicidal properties. In turfgrass, soil fumigants such as methyl bromide are used to control weeds prior to renovation of turf. Environmental concerns have resulted in deregistration of methyl bromide, prompting the need for alternatives. The objective of this research was to determine the effect of MSM on the establishment of selected turfgrass weeds as well as inhibitory effects on establishment of desirable turfgrasses. Greenhouse experiments were conducted in 2006 and 2007 at the University of Missouri. MSM was amended in soil at 0, 1,350 (low), 2,350 (medium), and 3,360 kg ha−1 (high) concentrations. Weed species included annual bluegrass, large crabgrass, buckhorn plantain, white clover, and common chickweed. Turfgrass species included: Rembrandt tall fescue, Evening Shade perennial rye, and Riviera bermudagrass. All species were seeded into soil amended with MSM and either tarped or left untarped. All treatments were compared to dazomet (392 kg ha−1), a synthetic standard. Plant counts and biomass of all species were recorded 4 wk after seeding. Overall, tarped treatments suppressed weed emergence 27 to 50% more compared to untarped treatments, except for large crabgrass. High rates of MSM suppressed emergence of all weeds ≥ 63%. Compared to the untreated control, the density of buckhorn plantain, white clover, and common chickweed was reduced by ≥ 42% at low rates of MSM. Biomass of buckhorn plantain, annual bluegrass, common chickweed, white clover, and large crabgrass was reduced from 37 to 99% at high rates of MSM. MSM at high rates reduced stand counts of tall fescue and perennial ryegrass up to 81% and 77% respectively, compared to the untreated control. Regardless of MSM rates or tarping, suppression of common bermudagrass emergence did not exceed 30%; tarped treatments actually increased bermudagrass emergence by 22%. The biomass for tall fescue, perennial ryegrass, and bermudagrass was reduced by 85, 68, and 10%, respectively, at high rates of MSM. For tall fescue, MSM at all rates strongly suppressed seed germination by 7 d after planting (DAP) (up to 100%), with additional germination observed through 14 DAP, but not thereafter. In both trials, dazomet completely suppressed emergence of all weeds. MSM appears to suppress emergence and growth of a number of weeds common in turf, with potential selectivity for bermudagrass.

Tolerance of sprigged ‘Tifsport’ and ‘Tifdwarf’ bermudagrass, ‘Meyer’ zoysiagrass, and ‘Salam’ seashore paspalum to oxadiazon (2,240 g/ha) or quinclorac (840 g/ha) applied 1 wk before sprigging (WBS), at sprigging (AS), 2 wk after sprigging (WAS), and 4 WAS was investigated in the field. Weed control was also evaluated. For both herbicides only the AS application timing injured the turfgrass greater than 22%, and injury for the other application timings ranged from 9 to 19% 5 WAS. When evaluated 8 WAS turfgrass injury following the AS application timing remained at 19%, and injury for all other timings was 8% or less. Eight WAS the 1 WBS, AS, 2 WAS, and 4 WAS application timings achieved 89, 79, 94, and 99% plot coverage, respectively, when averaged over all turfgrass species/cultivars and herbicides. By 13 WAS, all species/cultivars achieved at least 90% plot coverage. Presprigging applications of oxadiazon provided 98 to 100% goosegrass and old world diamond-flower control. Quinclorac applied AS provided greater than 70% control of these weeds. Results indicate that oxadiazon and quinclorac applied AS will cause unacceptable turfgrass injury. If goosegrass and/or old world diamond-flower are problematic, oxadiazon is a feasible choice for control of these weeds, but quinclorac is not.

The inclusion of winter cereals in spring-annual rotations in the northern Great Plains may reduce weed populations and herbicide requirements. A broad range of spring and winter cereals were compared for ability to suppress weeds and maximize grain yield at Lacombe (2002 to 2005) and Lethbridge (2003 to 2005), Alberta, Canada. High seeding rates (≥ 400 seeds/m2) were used in all years to maximize crop competitive ability. Spring cereals achieved high crop-plant densities (> 250 plants/m2) at most sites, but winter cereals had lower plant densities due to winterkill, particularly at Lethbridge in 2004. All winter cereals and spring barley were highly effective at reducing weed biomass at Lacombe for the first 3 yr of the study. Weed suppression was less consistently affected by winter cereals in the last year at Lacombe and at Lethbridge, primarily due to poor winter survival. Grain yields were highest for spring triticale and least for spring wheat at Lacombe, with winter cereals intermediate. At Lethbridge, winter cereals had higher grain yields in 2003 whereas spring cereals had higher yields in 2004 and 2005. Winter cereals were generally more effective at suppressing weed growth than spring cereals if a good crop stand was established, but overlap in weed-competitive ability among cultivars was considerable. This information will be used to enhance the sustainable production of winter and spring cereals in traditional and nontraditional agro-ecological zones.

Machine-vision cultivator guidance systems are commercially available to growers, but little work has been done to determine if these guidance systems can improve integrated weed management systems in vegetable crops. Studies were conducted in 2005 and 2006 in broccoli and lettuce to evaluate band-applied DCPA or pronamide, respectively, and four noncultivated bands ranging from 5.1 to 12.7 cm. DCPA or pronamide were applied in bands centered on the seed line at 0, 7.6 or 12.7 cm wide. A commercial machine-vision system was used to guide a commercial cultivator. Generally, weed densities and hand-weeding times were less where the DCPA band in broccoli or the pronamide band in lettuce were 7.6 or 12.7 cm wide compared to no herbicide. Weed densities were lowest in both crops where the noncultivated band width was 5.1 cm compared to 12.7-cm noncultivated bands. For broccoli in both 2005 and 2006, net returns above production costs were generally higher in the 7.6- and 12.7-cm-wide DCPA bands compared with the no-herbicide band. In lettuce in both years, the no-pronamide treatment had higher net returns, when compared with the 7.6- and 12.7-cm pronamide bands. Lettuce yields and higher net returns in the no-pronamide treatment compared to the 7.6- and 12.7-cm pronamide bands may be due to slight yield reduction from pronamide. Results suggest that pronamide was not needed during the dry months of the year when weed management tools such as hand-weeding and cultivation work very well. However, in periods of rainy weather when cultivation and hand-weeding are not possible, then pronamide would likely provide the greatest economic benefit. Given the large impact of cultivation on vegetable weed management programs, the greatest potential benefit of machine-vision guided cultivators is if they facilitate more timely and effective cultivation.

Research was conducted at Marianna, AR, for 2 yr to determine whether hairy vetch and Austrian winter pea cover crops would aid weed management programs in conservation-tilled, enhanced glyphosate-resistant cotton. Both cover crops were easily established and produced rapid growth in early spring, with biomass production of 435 to 491 g m−2 by Austrian winter pea and 415 to 438 g m−2 by hairy vetch. The effect of cover crops on weed control was short-lived in both years, with herbicide programs being the major determinant of weed control and seed-cotton yield. Averaged over cover crops, seed-cotton yields when the initial in-crop glyphosate application was delayed to the four-node cotton stage were up to 710 kg ha−1 less than in a PRE herbicide program. In 1 of 2 yr, seed-cotton yields were greater in PRE-treated plots compared with a program where initial weed management was delayed to the one-leaf stage of cotton. As a result of rapid decay of hairy vetch and Austrian winter pea biomass following cotton planting and the lack of adequate Palmer amaranth, pitted morningglory, and goosegrass control in the absence of herbicides, it appears there may be minimal weed management benefits from the use of hairy vetch and Austrian winter pea in Midsouth cotton production.

A study was conducted to evaluate the effect of imazosulfuron, halosulfuron, and trifloxysulfuron POST-directed on six fresh-market tomato varieties. Injury 7 d after treatment (DAT) was 3% or less from all treatments, and no injury was observed 28 DAT. Imazosulfuron, halosulfuron, and trifloxysulfuron did not reduce yield relative to the nontreated check. There was no detectable herbicide effect on fruit shape and earliness. Data suggest that imazosulfuron, halosulfuron, and trifloxysulfuron can be applied POST-directed without negatively affecting yield or quality of several fresh-market tomato varieties.

Field studies were conducted in wild blueberry in 2007 and 2008 to evaluate the efficacy of hexazinone applied PRE and multiple application timings of POST mesotrione on goldenrods and the efficacy of burning, terbacil applied PRE, nicosulfuron/rimsulfuron applied POST, and multiple application timings of mesotrione applied POST on black bulrush. Mesotrione application timings were at 10 and 30 cm of height, floral bud initiation, and full flower. Hexazinone applied at 1.92 kg ha−1 in 200 L water ha−1 effectively suppressed goldenrods. At least 90% goldenrod damage was achieved with mesotrione POST applied at 101 g ha−1 in 300 L water ha−1 before full flower, following hexazinone PRE at two of three sites. Damage following mesotrione was more variable when hexazinone was not applied. Mesotrione efficacy was lower when applied in the crop year, but a crop-year registration may be warranted to improve harvest ease and increase berry quality. A single application of mesotrione at the label rate did not adequately control black bulrush. Ninety percent black bulrush control was achieved with rimsulfuron/nicosulfuron applied at a rate of 0.03 g L−1 of water with 0.2% v/v nonionic surfactant. Equivalent levels of control were achieved with sequential mesotrione applications at the label rate.

Research was conducted to determine the effect of planting pattern, plant density, and levels of weed management intensity on intercepted photosynthetically active radiation (IPAR), weed control, and cotton lint yield in glyphosate-resistant cotton. Twin-row planting pattern canopy IPAR was 55% 7 wk after emergence (WAE) and 76% 9 WAE compared to 48% for single-row planting pattern 7 WAE and 59% 9 WAE. Regardless of cotton density, row spacing, or weed management intensity, control of browntop millet and Florida beggarweed was at least 88% 18 WAE. Benghal dayflower, sicklepod, and smallflower morningglory control was greater in twin-rows compared to single-rows at a cotton density of 7 plants m−2. Control of Benghal dayflower and sicklepod increased when cotton density increased at low weed management intensities; however, cotton density had no effect on weed control at higher levels of weed management input. At a cotton plant density of 7 plants m−2, twin-row cotton yielded 220 kg ha−1 more than the single-row planting pattern. Data indicates twin-row cotton production is feasible and that control of various weeds was better in twin-row than single-row pattern at lower cotton density and weed management intensity.

Miscanthus is a perennial rhizomatous C4 grass being evaluated in the United States as a potential bioenergy feedstock. Weed control during the first two growing seasons is essential for successful establishment. No herbicides are currently labeled for use in Miscanthus grown for biomass, but herbicides used on field corn might be safe to Miscanthus. Greenhouse experiments were conducted in 2007 and 2008 to evaluate the response of Miscanthus to numerous preemergence (PRE) and postemergence (POST) herbicides. Herbicides with activity only on broadleaf species, whether PRE or POST, did not exhibit injury or reduce Miscanthus biomass. Several herbicides, particularly those with significant activity on grass species, exhibited injury ranging from 6 to 71% (scale of 0 to 100) and/or reduced Miscanthus dry mass by 33 to 78%, especially at the highest rates applied. Field experiments were conducted in 2008 and 2009 with a selection of the herbicides used in the greenhouse experiments to evaluate the response of Miscanthus to herbicides applied PRE, POST and PRE followed by POST. Results from the field experiments generally confirmed those from the greenhouse experiments. PRE herbicides and herbicides with broadleaf-specific activity generally did not produce significant injury or reduce aboveground biomass while herbicides with grass activity tended to cause injury ranging from 22 to 25% and/or reduce biomass by 69 to 78%. With some exceptions, results support prior suppositions that herbicides used in corn are safe to use on Miscanthus and may provide potential herbicide options that growers can use when establishing Miscanthus.

Field research was conducted in 2000 and 2001 to determine the effect of yellow nutsedge emergence timing and plant density on soybean yield and on yellow nutsedge propagation the following year. Yellow nutsedge tubers were planted at 0-, 7.5- (13/m2), 15- (8.6/m2), 30- (4.3/m2), 60- (2.2/m2), and 90-cm (1.5/m2) in-row spacings with soybean. Yellow nutsedge densities from 2.2 to 13 plants/m2 in a high-yield year (2000) and 4.3 to 13 plants/m2 in a low-yield year (2001) reduced grain yields 9 to 34%. In a separate experiment, tubers were planted 0, 2, 4, 6, and 8 wk after planting at a 15-cm (8.6/m2) in-row spacing. Seedlings that emerged with the crop and until 2 wk after planting reduced yield 9 to 11%. Yellow nutsedge densities from 1.5 to 13 plants/m2 contributed to significant aboveground biomass production, even with a competitive crop, such as soybean. For every gram of aboveground yellow nutsedge biomass produced in the fall, there were more than four shoots present the following spring.

Alligator weed is a serious weed in many countries. In Australia, it is a “weed of national significance” because of its actual and potential impact. We surveyed all local governments in New South Wales in 2001 and 2007 to determine whether the weed is being contained. We found an increased number and extent of infestations, despite more resources and a better knowledge base. Most considered that further research is needed in tactics for control of the weed. On the basis of current containment in urban gardens, we recommend that governments better mobilize the community (e.g., bush restoration consultants, Landcare groups) to deal with alligator weed infestations.

Persistent use of herbicides has resulted in the selection of many herbicide-resistant weeds worldwide. A survey of 75 fields in the Palouse region of the inland Pacific Northwest was conducted to determine the extent of Italian ryegrass resistance to grass herbicides commonly used in winter wheat-cropping systems. Plants grown from collected seed samples were tested for resistance to diclofop, clodinafop, quizalofop, tralkoxydim, sethoxydim, clethodim, pinoxaden, triasulfuron, mesosulfuron, flucarbazone, imazamox, and flufenacet/metribuzin. Averaged across herbicide families within a herbicide group, some level of resistance was exhibited in 73, 31, and 31% of the populations to the aryloxyphenoxypropionates, cyclohexanediones, and phenylpyrazoline herbicides, respectively, and 39, 53, and 55% of the populations to the sulfonylureas, sulfonylaminocarbonyltriazolinone, and imidazolinone herbicides, respectively. Twelve percent of the populations showed some level of resistance to flufenacet/metribuzin. Cross-resistance to all acetyl coenzyme A carboxylase-inhibiting (group 1) herbicides was observed in 12% of the populations, whereas 25% of the populations were cross-resistant to all acetolactate synthase-inhibiting (group 2) herbicides tested. Of all the populations tested, 7% exhibited multiple resistance to at least one herbicide within all three groups tested. Only 5% of populations were completely susceptible to all 12 herbicides tested. These results indicate that herbicide-resistant Italian ryegrass populations are now common across much of the Palouse region in northern Idaho and eastern Washington.

Amicarbazone has potential for selective annual bluegrass control in cool-season turfgrasses, but seasonal application timings may influence efficacy. To test this hypothesis, field experiments in New Jersey and Indiana investigated amicarbazone efficacy from fall or spring applications and growth chamber experiments investigated the influence of temperature on efficacy. Fall treatments were more injurious to creeping bentgrass and Kentucky bluegrass than spring applications, but fall applications were also more efficacious for annual bluegrass control. In growth chamber experiments, injury and clipping weight reductions were exacerbated by increased temperatures from 10 to 30 C on annual bluegrass, creeping bentgrass, Kentucky bluegrass, and perennial ryegrass. Results suggest that amicarbazone use for annual bluegrass control in cool-season turf may be limited to spring applications, but increased temperature enhances activity on all grasses.

Field trials were conducted to evaluate imazosulfuron applied POST at 0.1, 0.2, 0.3, and 0.4 kg/ha to watermelon at the two- to four-leaf stage or to vines 30.5 cm long. At 7 d after treatment (DAT), crop injury to watermelon increased linearly for both growth stages as rate increased. The least injury to watermelon observed 7 DAT was 19 and 15%, respectively, for the two- to four-leaf and 30.5-cm growth stages treated with 0.01 kg/ha imazosulfuron. The 0.4 kg/ha imazosulfuron treatment caused the greatest watermelon injury (approximately 30%) at both application timings. Yield of watermelon treated with 0.1 and 0.2 kg/ha imazosulfuron applied at the two- to four-leaf and 30.5-cm stages were similar to the nontreated check (all plots were maintained weed-free). For both application timings, yield decreased linearly as imazosulfuron rate increased. The application of imazosulfuron to watermelon at the 30.5-cm stage averaged across rates resulted in less injury at 15 DAT (16%) and greater yield (92,869 kg/ha) than watermelon treated at two- to four-leaf stage averaged across rates (29%, 83,560 kg/ha). Internal fruit quality was not affected by imazosulfuron.

Glyphosate-resistance evolution in weeds is evident globally, especially in areas where transgenic glyphosate-resistant crops dominate. Resistance to glyphosate is currently known in 16 weed species, including rigid ryegrass in Australia. Following the first report of glyphosate resistance in 1998, there are now 78 documented glyphosate-resistant populations of rigid ryegrass in grain-growing regions of southern Australia. In some regions where glyphosate-resistance evolution has already occurred in rigid ryegrass, transgenic glyphosate-resistant canola was introduced in 2008, further highlighting the need to monitor glyphosate-resistance evolution in weeds. A rigid ryegrass population (WALR70) was collected in 2005 from a crop field in Esperance, Western Australia, after it had survived applications of glyphosate. Dose–response experiments confirmed resistance in the population, with the glyphosate rate resulting in 50% mortality (LD50) for WALR70 being 11 times greater than that for a susceptible biotype. The WALR70 population also had low levels of resistance to some acetyl coenzyme A carboxylase (ACCase)- and acetolactate synthase (ALS)-inhibiting herbicides (diclofop, fluazifop, clodinafop, tralkoxydim, chlorsulfuron, and imazethapyr), but was susceptible to other herbicide modes of action, such as atrazine, trifluralin, and paraquat. Two other rigid ryegrass populations assessed in this study were also confirmed to be resistant to glyphosate. The increasing number of glyphosate-resistant rigid ryegrass populations in Australia is of concern to growers because of the importance of glyphosate in intensive cropping systems and the introduction of glyphosate-resistant canola to this region.

Weeds cause crop loss indirectly by reducing the quantity of resources available for growth. Quantifying the effects of weed interference on nitrogen (N) supply, crop growth, and N nutrition may assist in making both N and weed management decisions. Experiments were conducted to quantify the effect of N addition and weed interference on soil nitrate-N (NO3-N) over time and the dependence of corn growth on NO3-N availability, determine the corn N nutrition index (NNI) at anthesis, and evaluate if relative chlorophyll content can be utilized as a reliable predictor of NNI. Urea was applied at 0, 60, and 120 kg N/ha to establish N treatments. Season-long weedy, weed-free, and five weed interference treatments were established by delaying weed control from time of crop planting to the V3, V6, V9, V15, or R1 stages of corn development. Soil NO3-N ranged from 20 kg N/ha without N addition to 98 kg N/ha with 120 kg N/ha added early in the season, but crop and weed growth reduced soil NO3-N to 10 kg N/ha by corn anthesis. Weed presence reduced soil NO3-N by up to 50%. Average available NO3-N explained 29 to 40% of the variation in corn shoot mass at maturity. Weed interference reduced corn biomass and NNI by 24 to 69%. Lack of N also reduced corn NNI by 13 to 46%, but reduced corn biomass by only 11 to 23%. Nondestructive measures of relative chlorophyll content predicted corn NNI with 65 to 85% accuracy. Although weed competition for factors other than N may be the major contributor to corn biomass reduction, the chlorophyll meter was a useful diagnostic tool for assessing the overall negative effects of weeds on corn productivity. Further research could develop management practices to guide supplemental N applications in response to weed competition.

The objective of this experiment was to determine the effectiveness and crop safety of glyphosate vs. alternative herbicides for weed control in glyphosate-resistant alfalfa. Glyphosate-resistant alfalfa was established at two sites in Pennsylvania in 2004 and in 2005, and herbicides were applied either PRE or POST for weed control. Data were collected on herbicide performance, alfalfa and weed yield, and forage quality. Alfalfa forage response to weed control was variable and depended on weed severity. A single or split application of glyphosate provided similar or better weed control than conventionally based herbicide programs. The most differences from weed control occurred during the first harvest and dissipated in subsequent harvests. Cumulative alfalfa yield for the establishment year of the spring seeding was 26% lower in the untreated check relative to the mean of the herbicide-treated plots in 2004; but no differences were detected in 2005. Forage quality was highest where weed content of the forage was lowest. Effective management of weeds with herbicides during alfalfa establishment can improve forage yield and quality, and weed control is particularly important when summer annual weed populations are severe and emerge with the crop.

Glyphosate applied to glyphosate-resistant (RR) cotton varieties after the four-leaf stage can decrease boll retention resulting in severe yield reductions. Enhanced glyphosate-resistant cotton (RR Flex), released for commercial use in 2006, offers a wider window of glyphosate applications without the risk of yield loss. However, no data exist regarding the effect of glyphosate application, especially late season applications, on fruit partitioning in RR Flex cotton. The objective of this research was to determine the effect of glyphosate rate and application timing on RR Flex cotton yield and fruit partitioning compared with current RR cotton. Studies were conducted during a 3-yr period (2004 to 2006), throughout the cotton growing regions of Mississippi. Roundup Ready (ST 4892 Bollgard/Roundup Ready [BR]) and Roundup Ready Flex (Mon 171 Enhanced Roundup Ready and ST 4554 Bollgard II/Roundup Ready Flex [B2RF]) cotton was planted, and glyphosate was applied at various rates and cotton growth stages. Data were collected using box mapping, a technique designed to depict yield partitioning on a cotton plant. RR Flex cotton yields were unaffected by glyphosate application timing or rate. Yields for ST 4892 BR were affected by application timings after the sixth leaf. ST 4892 BR had increased yield partitioning to position-three bolls and upper nodes with later application timings of glyphosate. Increases in seed cotton partitioned to higher nodes and outer fruiting positions were unable to compensate for fruit shed from innermost, lower fruiting sites. These data indicate that RR Flex cotton has excellent tolerance to late-season glyphosate applications.

Field studies were conducted in 2007 and 2008 near Nyssa, OR, and Pasco and Paterson, WA to evaluate yellow nutsedge and broadleaf weed control and potato tolerance to imazosulfuron. No injury symptoms from imazosulfuron were evident on potato at Nyssa, whereas in Washington, imazosulfuron caused some chlorosis of potato foliage ranging from 6 to 15% and < 4% at 6 and 15 d after POST application, respectively. Sequential applications of imazosulfuron controlled yellow nutsedge better than a single PRE application. Sequential applications of imazosulfuron or imazosulfuron in combination with s-metolachlor controlled yellow nutsedge > 92 and 89% at 21 and 42 d after POST applications, respectively. Imazosulfuron controlled ≥ 98% of common lambsquarters and 100% of pigweed species. Imazosulfuron provided season-long control of common mallow at Nyssa. However, imazosulfuron failed to control Russian thistle at Paterson, and only partially controlled hairy nightshade. Yield of U.S. no. 1 potato at Nyssa ranged from 44 to 54 T ha−1 and 42 to 52 T ha−1 for imazosulfuron PRE and imazosulfuron sequential treatments in 2007 and 2008, respectively. U.S. no. 1 potato yield following imazosulfuron PRE and sequential treatments at Pasco ranged from 49 to 57 T ha−1 in 2007, and at Paterson from 36 to 54 T ha−1 in 2008. Lower yields in 2008 were attributed to poor control of hairy nightshade. Imazosulfuron has potential to become a valuable tool for yellow nutsedge management in potato. Studies are needed to evaluate the soil persistence for imazosulfuron in order to determine safety to crops grown in rotation with potato.