Tiafenacil is registered in the United States for use in annual crops such as corn and soybean, but not on orchard crops. Field studies were conducted to determine orchard crop safety and efficacy of tiafenacil on important California orchard weeds. To evaluate crop safety, tiafenacil was applied at 74, 148, and 222 g ai ha−1 alone and with 38 g ai ha−1 of tolpyralate three times per year at the base of almond, pistachio, prune, and walnut trees. The first treatment was applied 2 mo after the trees had been transplanted. In all four tree crop experiments, treatments were applied once in May 2020, then three times again during the winter of 2021 and 2022 at 21-d treatment intervals. There were no visual foliar injury symptoms or treatment-related effects on tree trunk diameter change even at the highest tested rate of tiafenacil applied seven times over three growing seasons. In a separate study of weed control, in most instances, tiafenacil applied at 12 g ai ha−1 performed similarly to that of tiafenacil plus glufosinate. Control of glyphosate-resistant hairy fleabane with tiafenacil applied alone at 25 g ai ha−1 was 65% by 14 d after treatment. Tiafenacil applied at 50 g ai ha−1 to hairy fleabane performed similarly to glufosinate plus glyphosate. In a greenhouse study, tiafenacil applied at 12 g ha−1 provided 95% to 100% control of barnyardgrass and junglerice, and there was no significant difference between tiafenacil applied alone or with glufosinate. Saflufenacil applied alone or in a mixture with glufosinate was not as effective as the tiafenacil treatments for grass weed control. Based on experiments conducted over three growing seasons in four tree fruit and tree nut crops, tiafenacil crop safety appeared to be acceptable even at up to 2- or 3-fold the expected use rate.

Managing winter annual grass weeds has long been a challenge in the dryland regions of the Pacific Northwest (PNW) where soft white winter wheat is grown. The recent development of quizalofop-resistant (CoAXium) wheat varieties allows growers to use quizalofop (QP), a herbicide that inhibits acetyl-CoA carboxylase (ACCase) for postemergence grass control. Field experiments were conducted over two winter wheat growing seasons in 2021–2022 and 2022–2023 near Adams, OR, to evaluate QP efficacy on feral rye and for crop safety. Downy brome and jointed goatgrass control with QP were assessed in 2021–2022 and 2022–2023, respectively. QP treatments provided effective control of feral rye (≥95%), downy brome (≥87%), and jointed goatgrass (99%) regardless of rate, adjuvant, and spray volume tested. Spring-applied QP caused no injury to winter wheat. Results indicate that the QP-resistant wheat technology can help PNW wheat growers selectively control winter annual grasses.

Weed management in cantaloupe and other melon crops is important to maximize fruit yield; however, there are few registered herbicides available in California. Several independent herbicide trials were conducted at University of California field stations in Davis (Yolo County), Five Points (Fresno County), and Holtville (Imperial County) from 2013 to 2019 to evaluate both registered and unregistered herbicides and incorporation methods (sprinklers, cultivation, or none) for crop safety and weed control in melons. Although specific treatments varied among locations depending on local practice and research objectives, ethalfluralin and halosulfuron were used in all experiments, and bensulide and S-metolachlor were evaluated in 4 of 6 site-years. Additional herbicides included clethodim, clomazone, DCPA, napropamide, pendimethalin, sethoxydim, and sulfentrazone. Among registered herbicides, halosulfuron, halosulfuron + ethalfluralin, and ethalfluralin + bensulide combinations provided consistently beneficial weed control across all site-years compared to the nontreated control. S-metolachlor performed as well as the best of the registered herbicides tested at each site-year; although moderate injury was noted at the Davis location, this did not reduce melon yield. The method used to incorporate preplant herbicides had a significant impact on weed control efficacy but varied by location. Mechanical incorporation of preplant herbicides resulted in improved weed control and yield compared to sprinklers. Early-season weed control, whether by herbicides or hand weeding, resulted in significant yield increase in most site-years.

Northern highbush blueberry is an important fresh market product in New Jersey where the plant was first domesticated in the early 20th century. Because of the short period for safely and timely applying postemergence (POST) herbicides, reliance on residual herbicides that provide season-long control of weeds is essential for blueberry growers to minimize the detrimental effect of weed competition on berry yield and quality and bush growth. Field studies were conducted from 2018 to 2020 in Chatsworth, New Jersey, on ‘Bluecrop’, ‘Duke’, and ‘Elliott’ blueberry cultivars growing on sandy acidic soil to evaluate weed control and crop tolerance in response to repeated annual applications of indaziflam at 73 or 146 g ai ha−1 applied in fall or spring. The efficacy of indaziflam treatments were compared to those of fall-applied dichlobenil at 3,300 g ai ha−1 or a spring-applied mix of diuron at 1,800 g ai ha−1, oryzalin at 3,360 g ai ha−1, and mesotrione at 210 g ai ha−1. Indaziflam at the currently labeled rate of 73 g ai ha−1 provided ≥85% and season-long control of horseweed, Canadian toadflax, and large crabgrass with fall applications on dormant blueberry, whereas spring applications were less effective. Whereas minor (≤8%) and transient leaf crinkling was noted in response to spring-applied indaziflam at 146 g ai ha−1, a fall application never caused leaf crinkling greater than that observed in the nontreated weedy and weed-free controls, regardless of rate. No negative effects on plant growth or fruit production were observed from indaziflam applied at 73 or 146 g ai ha−1 in fall or spring. Findings of this study suggest that indaziflam applied at 73 (1× commercial use rate) and 146 g ai ha−1 is safe to use on blueberry grown on New Jersey sandy acidic soils despite restrictions for using this herbicide on such soils.

Dose-response trials to determine the tolerance of summer squash and watermelon to fomesafen applied (over the top of black polyethylene mulch and respective row middles) pre-transplanting were performed between 2020 and 2021 at three Indiana locations: the Meigs Horticulture Research Farm (MEIGS), the Pinney Purdue Agricultural Center (PPAC), and the Southwest Purdue Agricultural Center (SWPAC). Summer squash trials were performed at the MEIGS and PPAC locations, and watermelon trials were performed at the MEIGS and SWPAC locations. The experiments for both summer squash and watermelon had a split-plot arrangement in which the main plot was herbicide rate, and the subplot was cultivar. Summer squash injury included necrotic leaf margin, chlorosis, brown and white spots, and stunting. Fomesafen rates from 262 to 1,048 g ai ha−1 in 2020 at both locations, and from 280 to 1,120 g ai ha−1 in 2021 at MEIGS did not affect summer squash yield. However, in 2021 at PPAC, fomesafen applied at rates from 280 to 1,120 g ha−1 delayed summer squash harvest and decreased marketable yield from 95% to 61% compared with the nontreated control. Watermelon injury included bronzing and stunting. Fomesafen rates from 210 to 840 g ai ha−1 did not affect marketable watermelon yield or fruit number. Crop safety was attributed to rain, which washed off most of the herbicide from the polyethylene mulch before plants were transplanted or little to no rain after transplant. Injury was observed only when there was no rain before transplant followed by excessive rain shortly after transplant. Overall, the 1× rate used for each trial was safe for use 1 d before transplanting summer squash and 6 to 7 d before transplanting watermelon.

Palmer amaranth is the most problematic and troublesome weed in agronomic cropping systems in the United States. Acetolactate synthase (ALS) inhibitor and glyphosate-resistant (GR) Palmer amaranth has been confirmed in Nebraska and it is widespread in several counties. Soybean resistant to isoxaflutole/glufosinate/glyphosate has been developed that provides additional herbicide site of action for control of herbicide-resistant weeds. The objectives of this study were to evaluate herbicide programs for control of ALS inhibitor/GR Palmer amaranth and their effect on Palmer amaranth density and biomass, as well as soybean injury and yield in isoxaflutole/glufosinate/glyphosate–resistant soybean. Field experiments were conducted in a grower’s field infested with ALS inhibitor and GR Palmer amaranth near Carleton, Nebraska, in 2018 and 2019. Isoxaflutole applied alone or mixed with sulfentrazone/pyroxasulfone, flumioxazin/pyroxasulfone, or imazethapyr/saflufenacil/pyroxasulfone provided similar control (86%–99%) of Palmer amaranth 21 d after PRE (DAPRE). At 14 d after early-POST (DAEPOST), isoxaflutole applied PRE and PRE followed by (fb) POST controlled Palmer amaranth by 10% to 63% compared to 75% to 96% control with glufosinate applied EPOST in both years. A PRE herbicide fb glufosinate controlled Palmer amaranth 80% to 99% 21 d after late-POST (DALPOST) in 2018, and reduced density 89% to 100% in 2018 and 58% to 100% in 2019 at 14 DAEPOST. No soybean injury was observed from any of the herbicide programs tested in this study. Soybean yield in 2019 was relatively higher due to higher precipitation compared with 2018 with generally no differences between herbicide programs. This research indicates that herbicide programs are available for effective control of ALS inhibitor/GR Palmer amaranth in isoxaflutole/glufosinate/glyphosate-resistant soybean.

Field studies were conducted from 2009 through 2011 at the Sustainable Agriculture Research and Extension Center near Lingle, Wyoming, to evaluate great northern bean response to PRE flumioxazin mixed with either trifluralin, pendimethalin, or ethalfluralin. Seven treatments were arranged in a randomized complete block with three or four replicates y−1. The soil texture of the study site was loam in 2009 and 2011, and sandy loam in 2010. Soil organic matter ranged from 1.4% to 1.8%. Treatments included flumioxazin plus trifluralin, flumioxazin plus pendimethalin, flumioxazin plus ethalfluralin, ethalfluralin plus EPTC, imazamox plus bentazon (POST), hand-weeded control, and nontreated control. Dry bean density 4 wk after planting differed among herbicide treatments (P < 0.001). Treatments that included flumioxazin reduced dry bean density 54% compared with treatments without flumioxazin. Dry bean yield was influenced by dry bean density; on average, yield in flumioxazin-containing herbicide treatments was 30% less than treatments not containing flumioxazin, even though weed control was generally greater in flumioxazin treatments.

Studies were conducted at six locations across North Carolina to determine tolerance of ‘Sunbelt’ grape (bunch grape) and muscadine grape (‘Carlos’, ‘Triumph’, ‘Summit’) to indaziflam herbicide. Treatments included indaziflam (0, 50, 73 g ai ha–1) or flumioxazin (213 g ai ha–1) applied alone in April, and sequential applications of indaziflam (36, 50, 73 g ai ha–1) or flumioxazin (213 g ai ha–1) applied in April followed by the same rate applied in June. No crop injury was observed across locations. Muscadine yield was not affected by herbicide treatments. Yield of ‘Sunbelt’ grape increased with sequential applications of indaziflam at 73 g ha–1 when compared to a single application of indaziflam at 50 g ha–1 or flumioxazin at 213 g ha–1 in 2015. Sequential applications of flumioxazin at 213 g ha–1 reduced ‘Sunbelt’ yield compared to a single application of indaziflam at 73 g ha–1 in 2016. Trunk cross-sectional area was unaffected by herbicide treatments. Fruit quality (soluble solids concentration, titratable acidity, and pH) for muscadine and bunch grape was not affected by herbicide treatments. Indaziflam was safe to use at registered rates and could be integrated into weed management programs for southern US vineyards.

Greenhouse studies were conducted to determine the response of six corn hybrids and two soybean varieties to acetolactate synthase (ALS) inhibitor herbicides applied with terbufos and/or piperonyl butoxide (PBO), a mixed function oxidase (MFO) inhibitor. Field experiments also were conducted to determine the response of six corn hybrids to the combination treatments, terbufos plus ALS inhibitor herbicides and/or PBO and/or antidote. PBO at 0.33 kg/ha tank-mixed with nicosulfuron and primisulfuron injured the Northrup King 9283 corn hybrid. Great Lakes 584 corn was less sensitive than Northrup King 9283 to these combination treatments. Pioneer 3377 IR corn hybrid was resistant to the combination of nicosulfuron or primisulfuron plus PBO at 2 kg/ha and also to the combination treatments of imazethapyr herbicide plus PBO even though terbufos was previously applied. ICI 8532 IT, ICI 8532, and Pioneer 3377 hybrids were injured by the combination of nicosulfuron or primisulfuron and/or terbufos and/or PBO at 2 kg/ha. ICI 8532 IT corn hybrid was not injured by the combination treatment of imazethapyr or thifensulfuron and terbufos. In the field studies, Pioneer 3377 IR and Ciba 4393 RSC hybrids were resistant to sulfonylurea and imidazolinone herbicides even when applied with PBO regardless of the presence of terbufos. All treatments of chlorimuron plus terbufos caused considerable injury to ICI 8532 IT, ICI 8532, Pioneer 3377, and Ciba 4393, but not Pioneer 3377 IR and Ciba 4393 RSC. The combination of thifensulfuron with PBO injured Elgin ‘87 soybean, but the W20 soybean was tolerant to this combination treatment. Combination of imazethapyr with PBO did not affect the growth of Elgin ‘87 soybean.

Nine corn inbreds were selected from a test on 250 inbreds based on distinctly different response to herbicides. These inbreds showed up to 50,000-fold differences, which varied by inbred and herbicide. Only the inbred GA209 was sensitive to bentazon and the four sulfonylurea herbicides. GA209 and B90 were the most sensitive inbreds to the sulfonylurea herbicides. F2R was generally the most tolerant inbred. The pattern of herbicide tolerance varied greatly. For example, the relative tolerance of F2 to thifensulfuron was 12-fold more than to rimsulfuron while Mo17 was 56-fold more tolerant to rimsulfuron than thifensulfuron. F2 was fivefold more tolerant of chlorsulfuron than chlorimuron, whereas B80 was 100-fold the reverse. These inbreds provide a small subset of varieties to evaluate the large and inherent differences in herbicide tolerance of corn.

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

Metribuzin will control many problematic weed species in winter wheat in the mid-Atlantic states, including herbicide-resistant biotypes, but it has not been recommended due to crop safety concerns. In a three-year trial, metribuzin was applied at 105 or 210 g ai ha−1 to wheat at the PRE, 2-leaf (Feekes stage 1 to 2), early spring (Feekes stage 3 to 4), and late spring (Feekes stage 4 to 6) growth stages using wheat cultivars sensitive to metribuzin. Early spring applications had the least amount of injury, and injury at this timing was transient and yield was not reduced. Yield loss was observed with the other application timings in at least one out of three years. Rainfall shortly after application appears to increase the risk of wheat injury.

Field studies were conducted at Aberdeen, ID; Ontario, OR; and Paterson, WA, to evaluate potato tolerance to flumioxazin and sulfentrazone. In ‘Russet Burbank’ tolerance trials conducted in 2000 at ID, OR, and WA, sulfentrazone applied preemergence (PRE) at rates ranging from 105 to 280 g ai/ha caused significant injury consisting of stunting, leaf discoloration-blackening, and/or leaf malformation-crinkling at 4 wk after treatment (WAT). By 12 WAT, injury was ≤5%. At 4 WAT, flumioxazin applied PRE at 105 and 140 g ai/ha resulted in injury, whereas 53 g ai/ha did not cause significant injury. At 12 WAT, no visual injury was present at the ID site, whereas flumioxazin at 140 g/ha was still causing injury in WA. Regardless of initial injury, Russet Burbank tuber yields at ID, OR, and WA were not reduced as a result of any flumioxazin or sulfentrazone treatment compared with the nontreated controls. In potato variety tolerance trials conducted at ID in 2000 and at WA in 2002 with Russet Burbank, ‘Ranger Russet’, ‘Russet Norkotah’, and ‘Shepody’ and at ID in 2002 with those varieties plus ‘Alturas’ and ‘Bannock Russet’, early season injury caused by flumioxazin or sulfentrazone applied PRE at rates as high as 210 g ai/ha or 280 g/ha, respectively, occurred, but variety tuber yields were not reduced compared with nontreated control yields. In contrast, at ID in 2001, early injury caused by flumioxazin or sulfentrazone applied PRE at 105 or 210 g/ha translated to tuber yield reductions of all six varieties tested compared with the nontreated controls. At WA in 2001, Ranger Russet tuber yields were reduced by PRE applications of flumioxazin at 53 to 140 g/ha or sulfentrazone at 105 to 280 g/ha, and Shepody total tuber yields were reduced by all rates of PRE-applied sulfentrazone. Russet Burbank and Russet Norkotah tuber yields were unaffected by either herbicide. Unusual heat stress occurring early in the 2001 growing season at both locations may have compounded the effects of herbicide injury and, consequently, tuber yields were reduced in 2001, whereas injury occurring in 2000 or 2002 during relatively normal growing conditions did not translate to yield reductions.

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

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

Management of Italian ryegrass in cereal-based cropping systems continues to be a major production constraint in areas of the United States, including the soft white winter wheat producing regions of the Pacific Northwest. Pyroxasulfone is a soil-applied herbicide with the potential to control broadleaf and grass weed species, including grass weed biotypes resistant to group 1, 2, and 7 herbicides, in several crops for which registration has been completed or is pending, including wheat, corn, sunflower, dry bean, and soybean. Field experiments were conducted from 2006 through 2009 near Corvallis, OR, to evaluate the potential for Italian ryegrass control in winter wheat with applications of pyroxasulfone. Application rates of PRE treatments ranged from 0.05 to 0.15 kg ai ha−1. All treatments were compared to standard Italian ryegrass soil-applied herbicides used in winter wheat, including diuron, flufenacet, and flufenacet + metribuzin. Visual evaluations of Italian ryegrass and ivyleaf speedwell control and winter wheat injury were made at regular intervals following applications. Winter wheat yields were quantified at grain maturity. Ivyleaf speedwell control was variable, and Italian ryegrass control following pyroxasulfone applications ranged from 65 to 100% and was equal to control achieved with flufenacet and flufenacet + metribuzin treatments and greater than that achieved with diuron applications. Winter wheat injury from pyroxasulfone ranged from 0 to 8% and was most associated with the 0.15–kg ha−1 application rate. However, this early-season injury did not negatively impact winter wheat yield. Pyroxasulfone applied at the application rates and timings in these studies resulted in high levels of activity on Italian ryegrass and excellent winter wheat safety. Based on the results, pyroxasulfone has the potential to be used as a soil-applied herbicide in winter wheat for Italian ryegrass management and its utility for management of other important grass and broadleaf weeds of cereal-based cropping systems should be evaluated.

Field trials were conducted to determine potato response to parts per trillion (ppt) per weight concentrations of sulfometuron in soil. The herbicide was applied to achieve targeted, 0-d soil concentrations of 0, 7.5, 15, 30, 60, 120, 240, 480, and 960 ppt. Russet Burbank potatoes were planted immediately after application using standard agronomic practices. Based on midseason visual evaluations, root and tuber injury occurred with 0-d concentrations of only 7.5 ppt. Concentrations at or above 120 ppt caused a significant increase in number of tubers with deformities compared with the control. By the end of the growing season, 0-d concentrations between 120 and 240 ppt resulted in higher percentages of tubers with deformities, such as cracks, knobs, or folds. Using logistic models fit to U.S. No. 1 tuber yield and net return data, doses of 74, 156, and 324 ppt are predicted to result in 5, 10, and 20% U.S. No. 1 yield reductions, respectively. The model predicted a 20% net return loss, approximately $160/ha, occurring at 262 ppt, which is near the 240 ppt concentration determined by standard ANOVAs and means comparisons with single degree of freedom contrasts causing significant tuber quality and yield reductions in our study. Growers using the 240 ppt concentration as an indicator of a no-effect level would encounter actual losses too great to withstand. This modeling approach provides an initial attempt at giving growers the tools necessary for assessing potential losses.

Field trials were conducted with sulfentrazone at 53, 80, and 105 g ai/ha combined with 0, 420, and 560 g ai/ha metribuzin in a 3 by 3 factorial arrangement. Sulfentrazone and metribuzin combinations improved control of redroot pigweed, common lambsquarters, hairy nightshade, and volunteer oat compared with sulfentrazone applied alone. Kochia control was more than 90% regardless of metribuzin presence in the treatment. Sulfentrazone at 105 g/ha was needed for greater than 90% hairy nightshade control. Sulfentrazone alone or in combination with metribuzin did not provide greater than 89% volunteer oat control. Potato crop injury was less than 5% and total tuber yields increased as metribuzin rate increased from 0 to 560 g/ha, reflecting improved weed control as metribuzin rate increased.

Field experiments were conducted in 2003 and 2004 to evaluate the effects of reduced rates of glufosinate on development and yield of three nonglufosinate-resistant cotton varieties. The varieties evaluated were selected on their relative maturity with PayMaster (PM) 1218, early maturity; FiberMax (FM) 960, medium maturity; and Delta and Pine Land (DP) 555, late maturity. Rates of 47, 23, and 4.7 g ai/ha were applied, representing 10, 5, and 1% of the typical use rate per application of 467 g ai/ha, respectively. As might be expected, when averaged over varieties, the 10% rate showed more injury than the 5%, and the 5% rate caused more visual injury than the 1% rate. Pooled over timing and rate, PM1218 showed more injury (18%) than FM960 (7%), which showed more injury than DP555 (1%) 7 days after application (DAA) at the 10% rate. However, although PM1218 showed the most visual injury, this did not translate into delay in maturity or loss of lint yield. DP555 showed 70 kg ai/ha and 50 kg ai/ha lint yield loss when glufosinate was applied at the 10% rate on the fifth and eighth node stage, respectively. DP555 was delayed in maturity when glufosinate was applied at the 10% rate on the eighth node stage. FM960 showed 30 kg/ha lint yield loss when glufosinate was applied at the 10 and 5% rates at the fifth node stage. Maturity of FM960 was delayed with the 10 and 5% rates applied at the fifth node stage.

Weed control and potato response to halosulfuron applied alone POST and with rimsulfuron or S-ethyl dipropyl carbamothioate (EPTC) were evaluated in 2004 and 2005 near Paterson, WA. Potatoes were injured and exhibited chlorosis and stunted growth after halosulfuron applications of 18, 26, and 35 g/ha. Potato height was reduced 33 and 20% in late May by halosulfuron at 18 or 26 g/ha in 2004 and 2005, respectively. Halosulfuron applied alone failed to control hairy nightshade and large crabgrass. Total tuber yield and U.S. no. 1 yield were reduced 10% in halosulfuron-treated plots because of poor weed control and possibly herbicide injury. Tank-mixing rimsulfuron with halosulfuron improved control of hairy nightshade and large crabgrass and increased potato yield. Tank-mixing EPTC at 2 kg/ha with halosulfuron improved early-season hairy nightshade control, but weed control was poor at row closure. Rimsulfuron applied alone at 18 or 26 g/ha controlled hairy nightshade and large crabgrass without potato injury and resulted in the greatest potato yields.