A prepackaged mixture of desmedipham + phenmedipham was previously labeled for control of Amaranthus spp. in sugarbeet. Currently, there are no effective POST herbicide options to control glyphosate-resistant Palmer amaranth in sugarbeet. Sugarbeet growers are interested in using desmedipham + phenmedipham to control escaped Palmer amaranth. In 2019, a greenhouse experiment was initiated near Scottsbluff, NE, to determine the selectivity of desmedipham and phenmedipham between Palmer amaranth and sugarbeet. Three populations of Palmer amaranth and four sugarbeet hybrids were evaluated. Herbicide treatments consisted of desmedipham and phenmedipham applied singly or as mixtures at an equivalent rate. Herbicides were applied when Palmer amaranth and sugarbeet were at the cotyledon stage, or two true-leaf sugarbeet stage and when Palmer amaranth was 7 cm tall. The selectivity indices for desmedipham, phenmedipham, and desmedipham + phenmedipham were 1.61, 2.47, and 3.05, respectively, at the cotyledon stage. At the two true-leaf application stage, the highest rates of desmedipham and phenmedipham were associated with low mortality rates in sugarbeet, resulting in a failed response of death. The highest rates of desmedipham + phenmedipham caused a death response of sugarbeet; the selectivity index was 2.15. Desmedipham treatments resulted in lower LD50 estimates for Palmer amaranth compared to phenmedipham, indicating that desmedipham can provide greater levels of control for Palmer amaranth. However, desmedipham also caused greater injury in sugarbeet, producing lower LD50 estimates compared to phenmedipham. Desmedipham + phenmedipham provided 90% or greater control of cotyledon-size Palmer amaranth at a labeled rate but also caused high levels of sugarbeet injury. Neither desmedipham, phenmedipham, nor desmedipham + phenmedipham was able to control 7-cm tall Palmer amaranth at previously labeled rates. Results indicate that desmedipham + phenmedipham can only control Palmer amaranth if applied at the cotyledon stage and a high level of sugarbeet injury is acceptable.

Sugarbeet, grown for biofuel, is being considered as an alternate cool-season crop in the southeastern United States. Previous research identified ethofumesate PRE and phenmedipham + desmedipham POST as herbicides that controlled troublesome cool-season weeds in the region, specifically cutleaf evening-primrose. Research trials were conducted from 2014 through 2016 to evaluate an integrated system of sweep cultivation and reduced rates of ethofumesate PRE and/or phenmedipham+desmedipham POST for weed control in sugarbeet grown for biofuel. There were no interactions between the main effects of cultivation and herbicides for control of cutleaf evening-primrose and other cool-season species in two out of three years. Cultivation improved control of cool-season weeds, but the effect was largely independent of control provided by herbicides. Of the herbicide combinations evaluated, the best overall cool-season weed control was from systems that included either a 1/2X or 1X rate of phenmedipham+desmedipham POST. Either rate of ethofumesate PRE was less effective than phenmedipham+desmedipham POST. Despite improved cool-season weed control, sugarbeet yield was not affected by cultivation each year of the study. Sugarbeet yields were greater when treated with any herbicide combination that included either a 1/2X or 1X rate of phenmedipham+desmedipham POST compared with either rate of ethofumesate PRE alone or the nontreated control. These results indicate that cultivation has a very limited role in sugarbeet grown for biofuel. The premise of effective weed control based on an integration of cultivation and reduced herbicide rates does not appear to be viable for sugarbeet grown for biofuel.

Twelve sequential herbicide treatments were compared to cycloate (S-ethyl N-ethylthiocyclohexanecarbamate), a standard treatment, for control of annual weeds in sugarbeets (Beta vulgaris L.) in three field experiments conducted from 1971 through 1977. At harvest, seven sequential treatments had less than 10 annual broadleaf weeds per 30 m of row, whereas there were 40 broadleaf weeds per 30 m of row for the cycloate treatment. Four of these sequential treatments had significantly higher root yields and net returns than the cycloate treatment. Dependent on the sequential treatment and year, tonnage was increased 7.3 to 20.3 t/ha, and net returns $150 to $515/ha above those with cycloate. The most effective sequential treatment for control of weeds was a preplanting mixture of 2.2 kg/ha of ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] plus 1.7 kg/ha of diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} followed by a postemergence mixture of 0,6 kg/ha each of desmedipham [ethyl m-hydroxycarbanilate carbanilate (ester)] plus phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate). This sequential herbicide treatment increased root yields by an average of 20.3 t/ha and net returns by $515/ha above those with cycloate.

A field experiment was conducted for 2 yr near Scottsbluff, NE, to evaluate the growth and yield response of nine commercial sugarbeet cultivars to five postemergence herbicide mixtures applied two times. Sugarbeet cultivars varied in their response to herbicides. Three of the five postemergence herbicide mixtures reduced sugarbeet leaf area at 9 wk after planting (WAP), while two treatments had no significant effect. Root yield reductions from herbicide treatments ranged from 3 to 11% averaged over the nine cultivars. Two applications of desmedipham plus phenmedipham at 180 plus 180 g/ha reduced root yield 3% compared to untreated plots. Two applications of clopyralid at 100 g/ha, triflusulfuron at 18 g/ha, or ethofumesate at 160 g/ha plus desmedipham plus phenmedipham resulted in a 17, 29, and 22% reduction in leaf area at 9 WAR respectively, and a 6, 8, and 6% reduction in root yield, respectively, compared to untreated plots. Sethoxydim at 280 g/ha plus desmedipham plus phenmedipham did not cause additional sugarbeet injury.

Differences in susceptibility of sugarbeet (Beta vulgaris L.) to preemergence application of ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate], pyrazon [5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone], and TCA (trichloroacetic acid) were evaluated in several combination treatments. Exposure of plants to ethofumesate severely decreased epicuticular wax deposition on leaf surfaces. Separation of epicuticular wax into major components by gas-liquid chromatography indicated that ethofumesate decreased deposition of alkanes and sec-ketones, but increased the percentage of long-chain waxy esters. TCA also decreased deposition of alkane and ketone components, but not of waxy esters. Waxes were unaffected by pyrazon. Greater foliar absorption of 14C-ethofumesate, 14C-desmedipham [ethyl m-hydroxycarbanilate carbanilate (ester)], and 14C-ethofumesate + 14C-desmedipham was observed in plants that received preemergence treatments of ethofumesate plus TCA compared to pyrazon or a control.

Phenmedipham was registered for use at 1.1 to 1.7 kg ai/ha in 1970 and desmedipham at 1.1 to 1.4 kg ai/ha in 1974 for postemergence control of broadleaf weeds in sugarbeet. Phenmedipham was sold from 1970 through 1981 and desmedipham plus phenmedipham (1:1), as a premixed product, has been sold since 1982. Development of multiple applications of reduced rates began in 1972 primarily to reduce sugarbeet injury. The technique was promoted to farmers after 1976. Ahalf-rate of phenmedipham and/or desmedipham applied twice at a 5- to 7-d interval controlled weeds better and caused less sugarbeet injury than a single full-rate application, and allowed application to smaller than four-leaf sugarbeet. Suggested sugarbeet size for the first application changed from 4-leaf in 1970 to cotyledon to two-leaf in 1992. Earlier application to more susceptible small weeds allowed a further rate reduction. The use of soil-applied herbicides prior to phenmedipham and/or desmedipham increased weed control and sugarbeet injury. Application to small weeds and sugarbeet by air or by ground sprayers at spray pressures over 1040 kPa controlled weeds better and injured sugarbeet more than when applied by ground sprayers at 280 kPa. Desmedipham and phenmedipham rates presently are adjusted for sugarbeet size, application method, soil-applied herbicide, and environment. The suggested initial application rate of phenmedipham and/or desmedipham in 1992 was 0.13 to 0.28 kg/ha as compared with 1.1 to 1.7 kg/ha in 1970. A typical rate of desmedipham or desmedipham plus phenmedipham applied in 1992, including multiple application, was approximately 0.7 kg/ha less than typical rates from 1970 through 1977.

Field experiments conducted over a 7-yr period have demonstrated that common buckwheat (Fagopyrum esculentum Moench. cv. ‘Mancan’) has acceptable tolerance to many herbicides that are known to selectively control grass-type weeds in broadleaf crops. Herbicides for broadleaf weed control that showed some selectivity in common buckwheat were desmedipham {ethyl [3-[(phenylamino) carbonyl] oxy] phenyl] carbamate} applied postemergence and fluorochloridone {3-chloro-4-(chloromethyl)-1-[3-(trifluoromethyl)phenyl]-2-pyrrolidinone} applied either preplant soil incorporated or preemergence shallow incorporated. Tank mixtures of desmedipham plus sethoxydim {2-[1-(ethoxyimino)butyl-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} also showed adequate tolerance to common buckwheat at rates recommended for weed control in other crops.

Economical combinations of herbicides and hand labor for weeding sugarbeets (Beta vulgaris L.) in high and low weed densities were determined for irrigated production in the southern Great Plains. Ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] preplant incorporated, a 50:50 mixture of phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate) and desmedipham (ethyl m-hydroxycarbanilate carbanilate (ester)] sprayed postemergence on small weeds, and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) incorporated at layby controlled pigweed (Amaranthus spp.) and kochia [Kochia scoparia (L.) Schrad.] with acceptable selectivity in sugarbeets. Sucrose yield was identical for all methods of weed control. Using herbicides did not lower, and in some cases doubled, the total cost of weed control in an area with a low weed density. On the other hand, effective herbicide combinations saved $298 to $966/ha compared to total reliance on hand labor in an area with a high weed density. Elaborate combinations of herbicides were not justified even with heavy weed density. The last few weeds remaining in a field can be most economically removed by hand labor.

Field experiments were conducted near Scottsbluff, NE, to evaluate the selectivity of sequential POST applications of ethofumesate and triflusulfuron for weed control in sugarbeet. When applied alone ethofumesate and triflusulfuron reduced common lambsquarters, hairy nightshade, and redroot pigweed density while triflusulfuron also reduced kochia density compared with an untreated control. Combining ethofumesate with desmedipham plus phenmedipham increased sugarbeet injury compared with desmedipham plus phenmedipham. Combining triflusulfuron with desmedipham plus phenmedipham increased kochia control but did not increase sugarbeet injury over that obtained with desmedipham plus phenmedipham. Weed control and sugarbeet injury from herbicides generally were unaffected by application in 97 or 182 L/ha of water carrier. However, herbicide control of hairy nightshade in 1993 was greater with 97 than 182 L/ha of water carrier.

Calendula is an alternative oilseed crop whose seed oil is valued as a substitute for tung oil and a replacement for petroleum-based volatile organic compounds in paints and other coatings. Calendula tolerances to most POST-applied herbicides are unknown. Two POST-applied herbicides were tested for tolerance by calendula. Imazamethabenz at 0.44 kg ai ha−1 plus surfactant and desmedipham plus phenmedipham at 0.36 + 0.36 kg ai ha−1 were tolerated by calendula, but the latter herbicide must be applied after the four–leaf-pair stage of growth to avoid severe injury. Neither herbicide adversely affected calendula seed yield if applied at the four–leaf-pair stage. Because these herbicides can control several weed species, calendula tolerance to them may encourage more growers and crop advisors to test this new oilseed crop on commercial farms.

Field trials were conducted in 1999 and 2000 to determine the influence of weed size and the number of glyphosate or glufosinate applications on weed control and sugarbeet yield. Glyphosate at 840 g/ha or glufosinate at 390 g/ha was applied one, two, or three times, beginning when the average weed height was 3, 10, 15, or 25 cm. Two sequential applications of glyphosate applied to 10-cm weeds or three sequential applications of glufosinate applied to 3-cm weeds provided weed control comparable to three sequential applications of desmedipham plus phenmedipham plus triflusulfuron plus clopyralid. Weed control and sugarbeet root yield were optimal for two postemergence applications of glyphosate and for three applications of glufosinate. Glyphosate provided greater control of redroot pigweed and common lambsquarters than glufosinate. Sugarbeet sucrose yield with both glyphosate and glufosinate weed control programs was nearly 10,000 kg/ha. Compared with two sequential applications of glyphosate, sucrose yield of glyphosate-resistant sugarbeet was reduced 15% by three sequential applications of desmedipham plus phenmedipham plus triflusulfuron plus clopyralid. Sucrose yields were similar between three sequential applications of glufosinate and three applications of desmedipham plus phenmedipham plus triflusulfuron plus clopyralid.

Field trials were conducted at five sites from 2001 through 2003 to determine the influence on sugarbeet and weeds of repeated broadcast and banded reduced rates of desmedipham plus phenmedipham, triflusulfuron, and clopyralid in combination with either 1.5 or 3% v/v methylated seed oil (MSO). Desmedipham plus phenmedipham, triflusulfuron, and clopyralid were applied POST three times at 5 to 7 d intervals at either 25, 50, 75, or 100% of a 180 plus 180 plus 18 plus 100 g ai/ha dosage (full rate). When averaged over all herbicide rates, crop injury was 6% greater, but common lambsquarters control was 5% higher, and crop yield was 15% greater with broadcast compared with banded herbicide application. In most situations, adding MSO at 3% rather than 1.5% did not improve weed control. Sugarbeet injury was lowest (11%) and the average weed control was 86% when herbicide rates (with 1.5% MSO) were 25% of the full rate (microrate). Applying an herbicide rate (with 1.5% MSO) that was 50% of the full rate (half rate) increased crop injury from 11% with the microrate to 18% with the half rate and elevated average weed control from 86% with the microrate to 92% with the half rate. Common lambsquarters control increased from 81% with the microrate to 89% with the half rate. Sugarbeet root yield was 23 t/ha when no herbicide was used, 48 t/ha with the microrate, and 49 t/ha with the half rate compared with 54 t/ha when the full rate was applied without MSO. Increasing herbicide rates to 75% of the full rate (three-quarter rate) (with 1.5% MSO) increased crop injury to 27% and average weed control to 96%. Applying 1.5% MSO to the full rate increased crop injury to 35% with no improvement in average weed control over that achieved with the full rate without MSO.

Field experiments were conducted near Scottsbluff, NE, in 2001 and 2002 to compare economic aspects of glyphosate applied to different glyphosate-resistant sugar beet cultivars with that of conventional herbicide programs applied to near-equivalent, non–glyphosate-resistant conventional cultivars. Glyphosate applied two or three times at 2-wk intervals, beginning when weeds were 10 cm tall, provided excellent weed control, yield, and net economic return regardless of the glyphosate-resistant sugar beet cultivar. All conventional herbicide treatments resulted in similar net economic returns. Although the conventional sugar beet cultivars ‘HM 1640’ and ‘Beta 4546’ responded similarly to herbicide treatments with respect to sucrose content, ‘Beta 4546RR’ produced roots with 1% more sucrose than ‘HM 1640RR’. When averaged over herbicide treatments, a producer planting Beta 4546RR could afford to pay US $185/ha more for glyphosate-resistant technology as could a producer planting HM 1640RR. When averaged over cultivars and herbicide treatments, it is estimated that a producer could afford to pay an additional US $385/ha for glyphosate-resistant technology without decreasing net return.

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 trials were conducted from 2006 through 2008 to determine the influence of ethofumesate applied at planting followed by dimethenamid-p or s-metolachlor applied to emerged sugarbeet for late-season weed control in glyphosate-resistant sugarbeet. The entire plot area was kept weed-free until mid-June by applying glyphosate at the four- and eight-true-leaf sugarbeet growth stages. Glyphosate was not applied from mid-June until late-July to allow weed growth as a measure of the residual benefit from ethofumesate, dimethenamid-p, and s-metolachlor applied earlier in the growing season. Dimethenamid-p was not as effective as s-metolachlor in reducing weed density in mid-July. Late-season weed suppression from both s-metolachlor and dimethenamid-p benefitted from ethofumesate applied at planting. Dimethenamid-p applied when sugarbeet reached the six-true-leaf growth stage reduced weed density and sugarbeet injury more than earlier applications. The lowest weed density in mid-July was achieved when s-metolachlor was applied at the six- to eight-true-leaf sugarbeet growth stage compared to earlier growth stages. A planting time application of ethofumesate followed by two glyphosate applications plus s-metolachlor at the eight-true-leaf sugarbeet growth stage provided 89% more weed control in mid-July than glyphosate alone. Suppressing late-season weed development increased sugarbeet root yield 15% compared with areas not receiving ethofumesate and s-metolachlor.

Velvetleaf is one of the most significant and fastest spreading alien weeds in Europe, and it is a difficult weed to control in conventional sugarbeet. Laboratory experiments were carried out in 2007 and 2008 and field experiments were carried out in 2006, 2007, and 2008 with the aim of finding effective herbicide combinations and optimum timing of control. Herbicides containing the active ingredients phenmedipham, desmedipham, ethofumesate, clopyralid, and triflusulfuron were all tested at different timings. Phenmedipham + desmedipham + ethofumesate gave 87% velvetleaf control in pot experiments when applied at the growth stages of velvetleaf cotyledons and one true leaf, but only 27 to 42% control in field trials. Triflusulfuron gave 76% control in pot experiments and 83 to 88% control in field experiments. The timing of the first and second herbicide applications was very important: the first application of herbicides must be at the cotyledon stage of velvetleaf. A 1-wk delay in first application reduced herbicide efficacy by 8%. A 5-d period between the first and second treatments gave 93% control, while a 10-d period between the first and second treatments gave only 77% control. Sugarbeet yield decreased by 60 to 86% due to competition with velvetleaf when a standard herbicide combination (phenmedipham + desmedipham + ethofumesate) was used, and the velvetleaf produced between 6,700 and 14,800 seeds m−2. Inclusion of triflusulfuron in the herbicide treatment significantly reduced velvetleaf seed production to between 200 and 4,700 seeds m−2. In most cases, inclusion of triflusulfuron increased sugarbeet yield. Better velvetleaf control occurred in years when the sugarbeet canopy developed early and the index of leaf area of sugarbeet was higher.

Currently there are no herbicides registered for direct application to buckwheat for broadleaf weed control. This 4-yr Lithuanian study examined weed control using several rates of clopyralid alone or combined with a single rate of desmedipham. Most applications were applied at the 1-leaf stage of crop growth, however, one rate of clopyralid was applied pre-emergence (PRE) in 2 of the 4 yr. Buckwheat injury was evident within a few days after application (or emergence) with all treatments, but by harvest, no symptoms were evident. In the 2 yr with greatest weed densities, densities were reduced with increasing clopyralid rates alone or with desmediphan. However, weed biomass and density were similar to the nontreated control at harvest. Common lambsquarters, scentless mayweed, wild buckwheat, and narrowleaf hawksbeard were species that were best (> 40% density reduction) controlled with clopyralid. With few exceptions, buckwheat yield in all herbicide-treated plots was similar to the nontreated control. Because yield was not increased with these herbicides, other weed control benefits, such as reduced interference with harvesting equipment or less dockage due to weed seed contamination, must be carefully weighed against the costs of herbicide and application and crop injury that reduced early-season vigor.

Occurrence of glyphosate-resistant (GR) canola volunteers in GR sugar beet is a management concern for growers in the Northern Great Plains. Field experiments were conducted at the Southern Agricultural Research Center near Huntley, MT, in 2011 and 2012 to evaluate effective herbicide programs to control volunteer GR canola in GR sugar beet. Single POST application of triflusulfuron methyl alone at the two-leaf stage of sugar beet was more effective at 35 compared with 17.5 g ai ha−1. However, rate differences were not evident when triflusulfuron methyl was applied as a sequential POST (two-leaf followed by [fb] six-leaf stage of sugar beet) program (17.5 fb 17.5 or 35 fb 35 g ha−1). Volunteer GR canola plants in the sequential POST triflusulfuron methyl–containing treatments produced little biomass (11 to 15% of nontreated plots) but a significant amount of seeds (160 to 661 seeds m−2). Ethofumesate (4,200 g ai ha−1) PRE followed by sequential POST triflusulfuron methyl (17.5 or 35 g ha−1) provided effective control (94 to 98% at 30 d after treatment [DAT]), biomass reduction (97%), and seed prevention of volunteer GR canola. There was no additional advantage of adding either desmedipham + phenmedipham + ethofumesate premix (44.7 g ha−1) or ethofumesate (140 g ha−1) to the sequential POST triflusulfuron methyl–only treatments. The sequential POST ethofumesate-only (140 fb 140 g ha−1) treatment provided poor volunteer GR canola control at 30 DAT, and the noncontrolled plants produced 6,361 seeds m−2, which was comparable to the nontreated control (7,593 seeds m−2). Sequential POST triflusulfuron methyl–containing treatments reduced GR sugar beet root and sucrose yields to 18 and 20%, respectively. Consistent with GR canola control, sugar beet root and sucrose yields were highest (95 and 91% of hand-weeded plots, respectively) when the sequential POST triflusulfuron methyl–containing treatments were preceded by ethofumesate (4,200 g ha−1) PRE. Growers should utilize these effective herbicide programs to control volunteer GR canola in GR sugar beet. Because of high canola seed production potential, as evident from this research, control efforts should be aimed at preventing seed bank replenishment of the GR canola volunteers.

Field studies were conducted to investigate the effects of different rates of herbicides on weed control, agronomic characteristics, and quality of sugar beet at Shiraz, Iran, in 2000 and 2001. Separate and combined applications of herbicides, including 14 combinations and different rates of grass and broadleaf herbicides, at two rates were used. Herbicides reduced weed biomass compared with the weedy check. In both years, maximum reduction in weed biomass was observed with desmedipham plus phenmedipham plus ethofumesate at 0.23 + 0.23 + 0.23 kg ai/ha and desmedipham plus phenmedipham plus propaquizafop at 0.46 + 0.46 + 0.1 kg ai/ha. Efficacy of grass herbicides was reduced when they were combined with pyrazon. Highest crop injury in both years was observed with desmedipham plus phenmedipham plus ethofumesate at 0.23 + 0.23 + 0.23 kg/ ha. Highest and lowest root yields in both years were produced in weed-free and weedy check plots, respectively. All herbicide treatments produced lower sugar beet yields than the hand-weeded check. Of the herbicide treatments evaluated, the highest sugar beet yields were with desmedipham plus phenmedipham plus propaquizafop at 0.46 + 0.46 + 0.1 kg/ha in 2001 and with desmedipham plus phenmedipham plus ethofumesate at 0.23 + 0.23 + 0.23 kg/ha in 2000. Sucrose content and other sugar beet brei characteristics were not affected by the herbicide treatments.

Field experiments were conducted in northern Greece during 2001 and repeated in 2002 and 2004 to evaluate the effects of pronamide on sugar beet. Total leaf area, leaf area index (LAI), leaf and root dry weights, photosynthetic yield (quantum yield of photochemical energy conversion in photosystem II), chlorotic index, and yield components of sugar beet were monitored after pronamide application. Three sugar beet cultivars, ‘Avantage’, ‘Dorothea’, and ‘Bianca’, requiring short, intermediate, and long vegetative periods, respectively, were subjected to treatment. Pronamide was applied on sugar beet either as a double application of 0.63 kg ai ha−1 at the two- to four-leaf and 0.63 kg ai ha−1 at the four- to six-leaf stage or as a single application of 1.26 kg ai ha−1 performed at the latter leaf stage. Both application procedures were combined with a split application of phenmedipham at 0.04 kg ai ha−1 plus desmedipham at 0.04 kg ai ha−1 plus metamitron at 0.70 kg ai ha−1 plus ethofumesate at 0.10 kg ai ha−1 plus mineral oil at 0.50 L ha−1 applied POST at the cotyledon–to–two-leaf as well as at the four-leaf growth stages. Pronamide (both single and double application) initially caused chlorosis and reduction of sugar beet growth. LAI and photosynthetic yield were also significantly affected for a 2-mo period following the final application, after which the negative effects caused by pronamide were ameliorated. At harvest, sugar beet root and sugar yield, sucrose, K+, Na+, and N-amino acid concentrations were not affected by the herbicide treatments compared with those produced in weed-free and herbicide-free plots, indicating that all cultivars managed to overcome the transient pronamide stress. Regarding sugar beet cultivars, root and sugar yield of Avantage and Dorothea at harvest were higher than that of Bianca, whereas sucrose concentration of Avantage was the lowest. There was not an apparent relationship between the order of sugar yield per cultivar (Dorothea > Avantage > Bianca) and the length of the vegetative period (Avantage < Dorothea < Bianca).