Field studies were conducted to determine the effect of season of the year, sunlight exposure time, and mulch color on paraquat photodegradation rate on polyethylene mulch. Experiments were established in winter, spring, and summer, with white and black polyethylene mulch, and paraquat-applied films were exposed to sunlight for 1, 4, 8, 24, 30, 48, 72, or 96 h after herbicide application. There was significant effect of the season by mulch color by time of exposure interaction on paraquat concentration recovered from mulch eluants. Winter paraquat photodegradation was lower than during the other seasons. At 48 h of sunlight exposure, predicted photodegradation on white mulch was 67, 83, and 88%, during winter, spring, and summer, respectively, whereas these values were 66, 82, and 84% on black mulch. The difference in paraquat photodegradation in winter with respect to the other seasons may be attributed to reduced ultraviolet radiation in winter, when solar radiation has to penetrate a larger atmosphere mass. In practical terms, transplanting on paraquat-applied mulch requires a minimum of 96 h during the spring and summer seasons, when concentrations were 5% or less, whereas a longer waiting period might be necessary in the winter.

Field experiments were conducted during 3 yr in Thessaloniki, northern Greece, to determine the efficacy of various herbicides applied alone or in mixtures POST on hoary cress grown in winter wheat. Also, the efficacy of these herbicides on hoary cress generated from seed or root fragments was investigated in pot experiments. All herbicides except for ioxynil plus bromoxynil provided 90 to 100% control of hoary cress generated from seed and root fragments grown in pots. Ioxynil plus bromoxynil gave 84% control of hoary cress generated from seed, but only 66% control of plants generated from root fragments. In the field, mecoprop plus dicamba, imazamethabenz plus mecoprop plus dicamba, and triclopyr applied at the four- to eight-leaf stage provided, respectively, 87, 76, and 83% control of hoary cress (averaged over year and assessment time). Thifensulfuron plus tribenuron provided only 29% control. Chlorsulfuron plus dicamba, clopyralid plus MCPA, 2,4-D plus metosulam, and fluroxypyr provided intermediate hoary cress control. Furthermore, the least hoary cress emergence 52 wk after treatment appeared in plots treated with triclopyr. In addition, wheat grown in plots treated with mecoprop plus dicamba yielded more than wheat treated with the other herbicide treatments, and 55% more than wheat grown in nontreated plots. The results of this study indicate that very good control of hoary cress and high wheat yield can be obtained by the application of mecoprop plus dicamba at the four- to eight-leaf weed growth stage.

Field studies were conducted from 2000 to 2003 to determine the effectiveness of potato desiccants for late-season hairy nightshade control and also their effect on hairy nightshade seed germination. Commercial sulfuric acid at 280 L/ha controlled 94 to 99% of the hairy nightshade 1 wk after treatment (WAT) in all years. Diquat at 560 g/ha and glufosinate-ammonium at 420 g/ha provided at least 93% control 1 WAT in all years except 2003 when control did not exceed 72%. By 3 WAT, hairy nightshade control ranged from 93 to 100% for all treatments, including carfentrazone-ethyl at 56 g/ha, diquat at 420 g/ha, paraquat at 530 g/ha, and sulfuric acid (proprietary process) at 280 L/ha. Treatment of plants with desiccants did not affect germination of hairy nightshade seed, with the exception of a 7% reduction in germination by the higher rate of diquat in 2001 and 2002.

Field studies were conducted in 2001 and 2002 in the Black Sea Region of northern Turkey to determine the critical period for weed control (CPWC) in corn and the effects of weed interference on corn height. Treatments of increasing duration of weed interference and weed-free period were imposed at weekly intervals from 0 to 12 wk after crop emergence (WAE). The CPWC was determined with the use of 2.5, 5, and 10% acceptable yield loss levels by fitting logistic and Gompertz equations to relative yield data. With 5% yield loss level, the CPWC was 5 wk, starting at 0.2 WAE and ending at 5.2 WAE, which corresponded to the one- to five-leaf stage of corn. The CPWC increased to 8.9 wk, starting at 0 WAE and ending at 8.9 WAE, at the 2.5% yield loss level. At 10% yield loss level, the CPWC decreased to 1.7 wk, starting at 2.1 WAE and ending at 3.8 WAE.

Crop yield and weed control rating have been used to measure weed and crop response to weed management treatments, eliminate unacceptable weed management treatments, and select “best” treatments for recommendation to farmers. However, the mathematical relationship between crop yield and rated weed control has not been reported before from such treated screening experiments. Likewise, differences have not been reported before in rated weed control among experienced observers (i.e., reliability) when rating the same experiments and for an experienced observer over time (i.e., repeatability). Data from published experiments on zone herbicide application in field corn in which weeds reduced yield to various amounts were reanalyzed to examine these issues. For this study, relative corn yield was calculated as a percentage of the 1× broadcast herbicide rate for two observers and either three experimental site-years or their average. For observer A, relative corn yield (%) increased linearly as rated total weed control (%) increased for all 3 site-yr and their average. For observer B, equations were curvilinear in 2 of 3 site-yr. For both observers, equations accounted for little data variability in relative corn yield (r2 = 0.25 and 0.25 in site-year 1, respectively, 0.38 and 0.36 in site-year 2, 0.58 and 0.57 in site-year 3, and 0.43 and 0.42 for their average). When rated total weed control by observer A was graphed against that of observer B, the relationship was a nearly ideal 1:1 linear relationship in only 1 of 3 site-yr. In two other site-years, equations were nonlinear, indicating that one observer distinguished smaller differences between treatments at lower rated control than the other observer. Between-row total weed cover and in-row total weed height influenced observer weed control rating.

A field experiment was conducted in 1996 and 1997 to determine snap bean tolerance to halosulfuron based on crop injury, height, and yield. Halosulfuron was applied preemergence (PRE), postemergence (POST), and sequentially PRE followed by (fb) POST at 35, 53, and 70 g ai/ha, respectively. For comparison, a hand-weeded check was included. When data were averaged across years and halosulfuron rates, halosulfuron PRE, POST, and PRE fb POST provided similar yellow nutsedge control (74 to 82%) at snap bean harvest. Halosulfuron PRE resulted in 4% snap bean injury at harvest. Similarly, halosulfuron PRE fb POST resulted in 5% injury, while halosulfuron POST caused the most damage at 8%. Snap bean height at harvest was reduced 14% with halosulfuron POST compared to the weed-free check, with only 5 and 6% reduction caused by halosulfuron PRE and PRE fb POST, respectively. Halosulfuron POST reduced yield 39% compared to the weed-free check, while the PRE and PRE fb POST application timings produced yield similar to the check. When averaged across years and halosulfuron application timings, an increase in halosulfuron rate had no effect on yellow nutsedge control or snap bean yield. A linear trend was found for snap bean injury and plant height at harvest with snap bean injury increasing with an increase in halosulfuron rate while snap bean plant height decreased with an increase in halosulfuron rate. Application of halosulfuron PRE is the safest means to control yellow nutsedge in snap bean in North Carolina.

Tillage is used in sugarcane to control weeds, eliminate ruts caused by harvest, destroy residue from the previous crop, and incorporate fertilizer. The effect of weed control and tillage programs on sugarcane growth and yield and on economics was evaluated over two growing seasons. In the first study, weeds were effectively controlled with a March application of hexazinone at 0.59 kg ai/ha plus diuron at 2.10 kg ai/ha either banded or broadcast. When tillage of row shoulders and middles in March was eliminated, soil temperature in the sugarcane drill early in the season was equal to that where March tillage was performed. Sugarcane early and late season stalk population and sugarcane and sugar yield were each equivalent for the full season tillage (tillage of row shoulders and middles in March and in May) and the no-till programs. Elimination of a single tillage operation reduced cost $16.28/ha, and herbicide applied as a band rather than broadcast reduced cost $30.49/ ha. For the no-till program, with herbicide banded in March, net return was increased $32.56/ha. In a subsequent study conducted at five locations, weed control was excellent when either pendimethalin at 2.77 kg ai/ha plus metribuzin at 1.26 kg ai/ha or hexazinone plus diuron at 0.59 kg/ha and 2.10 kg/ha was used. When the March tillage was eliminated, sugar yield was increased 8.6% (620 kg/ ha), and net return was increased $152.68/ha compared with March tillage. When the May tillage was eliminated sugar yield was increased 8% (580 kg/ha), and net return was increased $143.88/ha compared with May tillage. A reduction in tillage cost accounted for only $16.28 of the increase in net return per hectare, with the remainder due to increased yield with the elimination of the tillage operation.

The effects of microtopographic position on soil microenvironment and weed populations in ridge-tilled soybean were evaluated on three farms in Iowa in 1989 and 1990. In both years, over all weed species (primarily giant foxtail, green foxtail, yellow foxtail, redroot pigweed, and Pennsylvania smartweed), seedling emergence was highest in late May and early June, with few seedlings emerging after mid-June. Weed populations were highest in May and early June, after which rotary hoeing and cultivation reduced weed numbers in all plots. Microtopographic position (row, shoulder, and furrow) had a large effect on soil microenvironment and weed populations. Furrows were the wettest position through most of the growing season. Rows were the warmest position early in the season and the coolest position late in the season. Cumulative weed emergence early in the season was closely related to growing degree days, which accumulated faster in the row position than the furrow position. Following rotary hoeing and cultivation, the row position had significantly more total weeds than the shoulder and furrow positions on all farms in August of both years.

It has been previously reported that POST-applied isoxaben can effectively control established hairy bittercress. Experiments were conducted to determine the relative importance of root vs. foliar entry of POST-applied isoxaben. At a common isoxaben rate of 0.56 kg/ha, foliar-only and foliar plus soil applications provided 10.5 and 23.3% control, respectively, as determined by fresh weight reduction. In contrast, soil-only application provided 47.0% control. Hairy bittercress foliar absorption of 14C–isoxaben did not exceed 15% of the amount applied after 72 h. Therefore, the comparatively less effectiveness of foliar-only applications may be attributed primarily to limited absorption. Minimal isoxaben concentration required to inhibit root growth of hydroponically grown hairy bittercress was 0.0025 mg/L. Higher concentrations were required to produce a response in the foliage. Sorption of isoxaben by pine bark rooting substrate, typical of what is used in container nursery production, exceeded 99% of amount applied after 36 h. Even with 99% sorption, the probable concentration within the aqueous phase remains sufficient to inhibit hairy bittercress root growth. Additional studies with 14C–isoxaben established that approximately 35% of the root-absorbed isoxaben was translocated into the foliage. Translocation from the roots into the foliage was reduced to 16% when the experiment was repeated during environmental conditions less favorable for vegetative growth (i.e., longer day length and higher temperature). Results indicate that the control of hairy bittercress with POST-applied isoxaben is likely the result of root absorption and root-growth inhibition. Expression of phytotoxicity within the foliage is also a component, but is dependent upon the root-absorbed isoxaben being translocated into the foliage. Extent of this translocation is dependent upon plant maturity and prevalent environmental conditions.

A host-specific fungus Colletotrichum truncatum strain 00-3B1 (Ct) was mixed with herbicides to improve the control of scentless chamomile, a noxious weed in western Canada. The compatibility of Ct conidia (spores) with herbicides was evaluated in vitro, and varying effects were observed with different products on spore germination. Clodinafop, glufosinate, MCPA, and 2,4-D ester were relatively benign and delayed the germination slightly, whereas dicamba, imazethapyr, metribuzin, and 2,4-D amine were noticeably more inhibitive. Bromoxynil, glyphosate, sethoxydim, and Merge® (spray adjuvant) were most inhibitive, showing >50% inhibition after 24 h. To determine potential synergy, Ct was applied at 7 × 106 spores/ml in tank mixtures with selected herbicides at 1× and 0.1× registered rates under greenhouse conditions. Combining Ct with MCPA, 2,4-D ester, clopyralid, or metribuzin at 1× rate resulted in synergistic or additive interaction on scentless chamomile, increasing weed control significantly when compared to Ct or herbicides applied alone. Similar applications of Ct with imazethapyr, 2,4-D amine, dicamba, or glyphosate were antagonistic. Treatments with Ct plus 1× metribuzin killed scentless chamomile completely, whereas neither Ct nor the herbicide alone caused plant death, suggesting the value of this tank mixture.

Tall ironweed is a troublesome perennial weed that infests cool-season grass pastures in Kentucky. Field experiments were conducted in 2000 through 2003 to evaluate the efficacy of fall-applied herbicides on established tall ironweed following a midsummer mowing. Triclopyr-containing treatments showed the greatest suppression of tall ironweed 12 mo after treatment (MAT), across all years. With triclopyr at 0.56 and 0.63 kg/ha, tall ironweed control was 80% or greater in 2 of the 3 yr. Dicamba initially provided 87% control 8 MAT in 2 of 3 yr and declined to less than 60% 12 MAT. Tall ironweed shoot density was also reduced 66% or more 12 MAT with fall-applied triclopyr-containing treatments. In contrast, tall ironweed density increased approximately twofold in dicamba-treated plots between 8 to 12 MAT in all 3 yr. The impact of herbicide treatment on dry matter (DM) yield of spring-seeded red clover (Trifolium pratense L.), tall ironweed, and forage grasses was also evaluated. Red clover DM yield in the herbicide-treated plots in 2002 showed no significant differences from the untreated control. However, red clover DM yield in 2003 was lowest for the two triclopyr + clopyralid treatments, indicating a decrease in DM production compared with that of the nontreated control. Results indicated that fall-applied triclopyr-containing herbicides following a midsummer mowing is an effective program for removing tall ironweed from grass pastures, but further research is needed to evaluate the establishment of red clover following herbicide treatment.

Field experiments were conducted in 2002 and 2003 to evaluate total POST weed control in corn with mixtures of mesotrione, atrazine, and the commercial mixture of nicosulfuron plus rimsulfuron plus atrazine at registered and reduced rates. Treatments were compared with nicosulfuron plus rimsulfuron plus atrazine POST, and S-metolachlor plus atrazine PRE alone and followed by (fb) nicosulfuron plus rimsulfuron plus atrazine POST. All treatments controlled common lambsquarters 8 wk after the postemergence treatments (WAPT). Common ragweed control with POST mesotrione plus nicosulfuron plus rimsulfuron plus atrazine combinations was greater than 89%. Mesotrione plus the registered rate of nicosulfuron plus rimsulfuron plus atrazine POST controlled common ragweed more effectively than the PRE treatment alone. Addition of atrazine to mesotrione improved common ragweed control by at least 38 percentage points over mesotrione alone. Nicosulfuron plus rimsulfuron plus atrazine at the registered rate and in mixtures with mesotrione controlled morningglory species (pitted and ivyleaf morningglory) 89 to 91%. Large crabgrass control varied between 2002 and 2003. In 2002, large crabgrass control was 58 to 76% with all POST treatments, but in 2003, nicosulfuron plus rimsulfuron plus atrazine POST alone controlled large crabgrass greater than 86%. Large crabgrass was more effectively controlled by treatments with S-metolachlor plus atrazine PRE than by the total POST treatments in 2002. Giant foxtail was controlled at least 97% with nicosulfuron plus rimsulfuron plus atrazine treatments. S-metolachlor plus atrazine PRE fb nicosulfuron plus rimsulfuron plus atrazine POST controlled all weed species greater than 85%. Corn yields by total POST treatment combinations of mesotrione plus either rate of nicosulfuron plus rimsulfuron plus atrazine were comparable to S-metolachlor plus atrazine PRE alone or fb nicosulfuron plus rimsulfuron plus atrazine POST.

Field studies were conducted to assess the tolerance of seashore paspalum (‘Salam’) to postemergence (POST) herbicides in Florida in 2000 and 2001. POST applications of bentazon (2,200 g/ha), clopyralid (420 g/ha), dicamba (280 g/ha), halosulfuron (70 g/ha), imazaquin (420 g/ha), mecoprop + 2,4-D + dicamba (160 + 180 + 40 g/ha), metsulfuron (30 g/ha), and quinclorac (1,700 g/ha) resulted in ≤10% injury 7 and 15 d after treatment (DAT), indicating their safety for POST application. Clethodim (280 g/ha) and sethoxydim (310 g/ha) caused 67 and 46% injury, respectively, 15 DAT averaged across 2000 and 2001. Ethofumesate was inconsistent between years, causing 30 and 60% injury 7 and 15 DAT, respectively, in 2000, but only 5 and 13% 7 and 15 DAT, respectively, in 2001. Imazapic and trifloxysulfuron-sodium caused an average of 47% injury 7 DAT in 2000 and 45% injury 15 DAT in 2001. Clethodim, ethofumesate, imazapic, sethoxydim, and trifloxysulfuron-sodium can not be safely applied POST to Salam seashore paspalum; however, bentazon, clopyralid, dicamba, halosulfuron, imazaquin, mecoprop + 2,4-D + dicamba, metsulfuron, and quinclorac are safe.

Field studies were conducted at Fayetteville, Arkansas, to determine whether 47 Palmer amaranth accessions from different areas of the southern United States varied in response to postemergence applications of the registered rates of the isopropylamine salt of glyphosate (840 g ae/ha), fomesafen (420 g ai/ha), and pyrithiobac (70 g ai/ha). Glyphosate controlled all Palmer amaranth accessions at least 99% 21 d after treatment (DAT). Palmer amaranth control with fomesafen was equivalent for all accessions and at least 96% 21 DAT. Percent dry weight reductions were at least 92 and 94% for glyphosate and fomesafen, respectively. Palmer amaranth control with pyrithiobac was variable and ranged from 20 to 94% 21 DAT, but differences could not be attributed to accession origin. Herbicides with alternate modes of action from pyrithiobac should be utilized for Palmer amaranth control in regions where pyrithiobac has been used continuously.

Sand stockpiles, located near commercial cranberry beds in Massachusetts, New Jersey, Washington, and Wisconsin, were sampled quarterly over a 2-yr period. Samples were collected from the surface and the interior of the piles. Utilizing a simple greenhouse germination bioassay, 74 plant species representing 23 plant families were identified across all locations and samples. Plant density varied by region and by sampling depth; species richness varied by region only. More seedlings germinated from samples taken from the surface of the stockpile compared with interior samples. Almost half of all species detected in either surface or interior samples were represented by only one seedling. Fifty-nine percent of the plant species from Massachusetts and New Jersey samples, and 79% and 96% of the plant species from Wisconsin and Washington, respectively, were considered to be weeds in cranberry production. Only one-third of the identified species had wind-blown seeds; seed dispersal was by other mechanisms in almost half of the species. This survey documented the weed management implications of spreading stockpiled sand on cranberry bogs for horticultural or pest management purposes. To minimize the introduction of additional weed problems, growers and integrated pest management consultants should evaluate the seedbank potential of a stockpile prior to application of the sand to the production area.

Experiments were conducted at three locations in Louisiana in 2002 and 2003 to evaluate flumioxazin (36, 72, or 109 g ai/ha) applied pretransplant (PRE) or post-transplant (POST) to sweetpotato. All treatments were applied immediately before or after sweetpotato transplanting to weed-free beds. PRE applications caused 4% or less injury with any rate of flumioxazin at 9 or 18 d after transplanting (DATr) compared with 18 to 20% injury at 9 DATr and 6 to 14% at 18 DATr with 72 or 109 g/ha POST, respectively. Injury from PRE applications of flumioxazin were not different from injury with clomazone (840 g ai/ha) applied POST. Injury at Chase, LA, in 2002 was 8% and less with flumioxazin PRE, but 35 to 83% with flumioxazin POST and appeared to be due to the use of greenhouse-grown cuttings instead of field-grown cuttings, which were used in the other two experiments. There was no interaction between experiments for sweetpotato yield. Plots treated with flumioxazin PRE or 36 g/ha POST yielded greater than sweetpotato treated with clomazone for U.S. No. 1 and 2 grade yield as well as total marketable yield. No differences were observed in yellow nutsedge control with any rate of flumioxazin. At 34 or 50 DATr, flumioxazin controlled yellow nutsedge 73 to 85% with 72 or 109 g/ha applied PRE or POST. Flumioxazin, regardless of application timing or rate, controlled carpetweed and spiny amaranth at least 86%. A similar experiment in Mississippi evaluated tank-mixes of flumioxazin (36, 72, or 109 g/ha) and clomazone (840 g/ha) applied PRE or POST. No sweetpotato injury was observed with flumioxazin PRE. However, injury from flumioxazin POST increased with increased rates (18 to 50% at 18 DATr and 16 to 93% at 25 DATr). Weed control was greater than 80% with all treatments.

Response of ‘Dixie’, ‘Lemondrop’, ‘Multipik’, ‘Superpik’, and ‘Seneca Prolific’ summer squash to halosulfuron PRE or POST at 0.036, 0.053, and 0.072 kg ai/ha, or halosulfuron PRE fb halosulfuron POST at 0.018 fb 0.018, 0.027 fb 0.027, and 0.036 fb 0.036 kg/ha was field evaluated in 1997 and 1998. All halosulfuron treatments and rates reduced the height of cultivars 17–19% at 6 WAP (weeks after planting) and summer-squash injury (chlorosis and necrosis of crop foliage) was 6, 14, and 11% from halosulfuron PRE, POST, and PRE fb POST, respectively. Early summer-squash flowering was reduced 32–82% by halosulfuron, resulting in reduced early yields. Dixie was the cultivar most tolerant to halosulfuron. Early flowering of Dixie was reduced 32–36% compared to 32–82% for the other cultivars. Marketable yield of summer squash was reduced 20–30% by all rates of halosulfuron when averaged over all application timings. Marketable yield of Seneca Prolific, Superpik, Dixie, Multipik, and Lemondrop was reduced 0–17% by halosulfuron PRE. Halosulfuron POST or PRE fb POST reduced marketable yield of all summer-squash cultivars by 25–46%. Thus, summer squash was not tolerant of POST halosulfuron; however, Dixie, Multipik, Seneca Prolific, and Superpik exhibited tolerance to halosulfuron PRE.

Creeping bentgrass infestations in cool-season turfgrass are unsightly and difficult to control. Field tests were conducted at Stoney Creek Golf Course in Wintergreen, VA, in 2002 and 2003 on a Kentucky bluegrass rough and at the Turfgrass Research Center in Blacksburg, VA, in 2003 on a perennial ryegrass lawn to determine the efficacy of imazaquin, isoxaflutole, and mesotrione for creeping bentgrass control and turfgrass tolerance. Isoxaflutole and mesotrione each applied in two sequential applications at 280 g ai/ha or three sequential applications at 170 or 60 g/ha and imazaquin in two sequential applications at 390 g/ha controlled bentgrass at least 92% 14 wk after initial treatment (WAIT) at all locations. Sequential applications were applied at 2-wk intervals. Isoxaflutole and mesotrione, regardless of rate or sequential treatment, injured turfgrass less than 20% at all rating dates and locations. Imazaquin in two sequential applications at 390 g/ha injured Kentucky bluegrass and perennial ryegrass greater than 50% at all locations 14 WAIT. Results indicate isoxaflutole or mesotrione could be used for selective bentgrass control in Kentucky bluegrass or perennial ryegrass.

Field experiments were conducted to evaluate the effect of five spray-nozzle types and three drift-control adjuvants (DCA) on glyphosate spray drift. The extended-range (XR) flat-fan nozzle at 280 kPa was used as the standard comparison. DCAs were evaluated for drift reduction with the use of the XR and air-induction (AI) nozzles. Wind speed ranged from 1.3 to 9.4 m/s (3 to 21 mph). Lethal drift (DL) and injury drift (DI) were determined by downwind visual observation of grain sorghum response. Drift distances were measured from the spray swath edge. The Turbo FloodJet and AI nozzles reduced DL distance by 34%. All four drift-reducing (DR) nozzles reduced DI distance by 22 to 32%. Reducing the pressure of the XR flat-fan nozzle from 280 to 140 kPa did not reduce DL or DI distance. When applied through AI nozzles, each DCA increased droplet volume diameter, one DCA reduced DI distance and none reduced DL distance when applied through XR tips. The DCAs did not affect DL or DI distance.

Sunflower lines developed to resist some acetolactate synthase (ALS)-inhibiting herbicides are susceptible to foliar applications of other ALS-inhibiting herbicides. Research was conducted to determine whether imidazolinone (IMI)- or sulfonylurea (SU)-resistant sunflower was affected by soil residues of imazethapyr, metsulfuron, or flucarbazone. In greenhouse experiments, IMI-sunflower displayed 60 and 66% injury 4 wk after emergence with incorporated soil residues of metsulfuron at 4.2 g ai/ha and flucarbazone at 30 g ai/ha, respectively, but response to imazethapyr at 35 g ai/ ha was not different from that of nontreated plants. Metsulfuron at 4.2 g/ha and flucarbazone at 30 g/ha resulted in 56 and 72% less biomass accumulation, respectively, of IMI-sunflower compared with that of nontreated plants. Incorporated soil residues of imazethapyr, metsulfuron, or flucarbazone did not cause significant injury or result in shorter plants or less biomass accumulation of SU-sunflower than nontreated sunflower in greenhouse experiments. In field experiments, nonincorporated residues of imazethapyr, metsulfuron, or flucarbazone did not induce visible chlorosis or significant stunting of IMI- or SU-sunflower compared with nontreated sunflower. Herbicide-resistant sunflower growing in soil with nonincorporated residues of imazethapyr, metsulfuron, or flucarbazone produced seed yield similar to sunflower growing in sulfentrazone-treated soil or nontreated soil.