Wild oat is a herbicide resistance-prone global weed species that causes significant economic losses in dryland and horticultural agriculture. As a result, there has been a significant research effort to control this species. A major impediment to this research is the seed coat-mediated dormancy of wild oat, which requires a labor-intensive incision or puncturing of the seed coat to initiate seed germination. This study defines the most efficient settings of a mechanical thresher to overcome wild oat seed dormancy and then validates these settings using multiple populations collected from the Western Australian grain belt. We also compare the effects of rapid mechanical scarification and known germination stimulus tactics such as scarification with sulfuric acid (H2SO4), partial endosperm removal, sandpaper scarification of the seed coat, and immersion in sodium nitroprusside (NO donor SNP) solution on wild oat seedling growth rate. Threshing treatment of 1,500 rpm for 5 s provides equivalent germination compared with manually puncturing individual wild oat seeds, with no difference in seedling relative growth rate. The mechanical scarification of seeds using the thresher resulted in greater germination (66%) than H2SO4 scarification (0%), partial endosperm removal (10%), sandpaper seed coat scarification (25%), and exposure to NO donor SNP (34%). This study demonstrates that the physical dormancy of wild oat can be rapidly overcome using a commercially available mechanical thresher.

Smutgrass, a native of tropical Asia, is a perennial weed that affects many improved perennial grass pastures in Florida and throughout the southeastern United States. The two varieties of smutgrass predominant in Florida are small smutgrass and giant smutgrass. Three field experiments were conducted from 2008 to 2012 to evaluate the effect of integrated long-term management strategies using both cultural and herbicide inputs for giant smutgrass control in bahiagrass pastures. Burning did not have a significant impact on long-term control. In 2011, no differences were observed when hexazinone was integrated with tillage or hexazinone was combined with supplemental nitrogen compared with sequential or single applications of hexazinone. However, cultural treatments that preceded hexazinone application compared with those that received two sequential applications of hexazinone had lower smutgrass control 36 mo after treatment. Data indicate that a sequential application of hexazinone may be better than implementing tillage. Sequential hexazinone applications, when applied at 0.56 kg ai ha−1 or greater, resulted in similar or increased control as compared with single applications. Collectively, these data suggest that sequential applications of hexazinone may be most effective for smutgrass management, and cultural techniques, including tillage, should be followed by hexazinone application the following year.

Introduction and rapid adoption of dicamba-resistant (DR) soybean led to an increase of postemergent applications of dicamba. This resulted in a widespread increase in nontarget dicamba injury to non-DR soybean in 2017. Field studies were conducted in Manhattan, KS, in 2018 and 2019 and in Ottawa, KS, in 2019 to investigate the injury and yield response of soybean varieties with varying herbicide-resistance traits and maturity groups when exposed to dicamba. Four varieties were tested: ‘Credenz 3841LL’ (glufosinate resistant), ‘Credenz 4748LL’ (glufosinate resistant), ‘Asgrow AG4135RR2Y’ (glyphosate resistant), and ‘Stine 40BA02’ (glyphosate and isoxaflutole resistant), abbreviated as CR3841, CR4748, AG4135, and ST40B, respectively. Soybeans were treated with 5.6 g ae ha−1 of dicamba at V3 and R1 stages. Percent soybean injury, soybean height, soybean yield and yield components, and injury to offspring were evaluated. Four weeks after treatment (WAT) at V3, the greatest injury was observed in AG4135 and ST40B. Dicamba application at R1 resulted in the greatest injury to ST40B both 4 WAT and at senescence. Minimal injury was observed in all varieties treated at V3 at senescence and yield loss was 5% or less. Dicamba application at R1 resulted in 19 to 34% yield loss, with the least yield loss in CR4748, and the greatest in ST40B. Varieties with greater injury at senescence generally yielded less than other varieties.

POST goosegrass and other grassy weed control in bermudagrass is problematic. Fewer herbicides that can control goosegrass are available due to regulatory pressure and herbicide resistance. Alternative herbicide options that offer effective control are needed. Previous research demonstrates that topramezone controls goosegrass, crabgrass, and other weed species; however, injury to bermudagrass may be unacceptable. The objective of this research was to evaluate the safening potential of topramezone combinations with different additives on bermudagrass. Field trials were conducted at Auburn University during summer and fall from 2015 to 2018 and 2017 to 2018, respectively. Treatments included topramezone mixtures and methylated seed oil applied in combination with five different additives: triclopyr, green turf pigment, green turf paint, ammonium sulfate, and chelated iron. Bermudagrass bleaching and necrosis symptoms were visually rated. Normalized-difference vegetative index measurements and clipping yield data were also collected. Topramezone plus chelated iron, as well as topramezone plus triclopyr, reduced bleaching potential the best; however, the combination of topramezone plus triclopyr resulted in necrosis that outweighed reductions in bleaching. Masking agents such as green turf paint and green turf pigment were ineffective in reducing injury when applied with topramezone. The combination of topramezone plus ammonium sulfate should be avoided because of the high level of necrosis. Topramezone-associated bleaching symptoms were transient and lasted 7 to 14 d on average. Findings from this research suggest that chelated iron added to topramezone and methylated seed oil mixtures acted as a safener on bermudagrass.

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.

A major concern of sweetpotato producers is the potential negative effects from herbicide drift or sprayer contamination events when dicamba is applied to nearby dicamba-resistant crops. A field study was initiated in 2014 and repeated in 2015 to assess the effects of reduced rates of N,N-Bis-(3-aminopropyl)methylamine (BAPMA) or diglycloamine (DGA) salt of dicamba, glyphosate, or a combination of these individually in separate trials with glyphosate on sweetpotato. Reduced rates of 1/10, 1/100, 1/250, 1/500, 1/750, and 1/1,000 of the 1× use rate of each dicamba formulation at 0.56 kg ha−1, glyphosate at 1.12 kg ha−1, and a combination of the two at aforementioned rates were applied to ‘Beauregard’ sweetpotato at storage root formation (10 d after transplanting) in one trial and storage root development (30 d after transplanting) in a separate trial. Injury with each salt of dicamba (BAPMA or DGA) applied alone or with glyphosate was generally equal to or greater than glyphosate applied alone at equivalent rates, indicating that injury is most attributable to the dicamba in the combination. There was a quadratic increase in crop injury and a quadratic decrease in crop yield (with respect to most yield grades) observed with an increased herbicide rate of dicamba applied alone or in combination with glyphosate applied at storage root development. However, with a few exceptions, neither this relationship nor the significance of herbicide rate was observed on crop injury or sweetpotato yield when herbicide application occurred at the storage root formation stage. In general, crop injury and yield reduction were greatest at the highest rate (1/10×) of either salt of dicamba applied alone or in combination with glyphosate, although injury observed at lower rates would be cause for concern after initial observation by sweetpotato producers. However, in some cases yield reduction of No.1 and marketable grades was observed following 1/250×, 1/100×, or 1/10× application rates of dicamba alone or with glyphosate when applied at storage root development.

Weed control in corn is a major challenge due to increasing problems with highly dominant weed species and herbicide resistance evolution. Common lambsquarters and johnsongrass constitute up to 80% to 90% of the weed population in many spring crops, such as soybean [Glycine max (L.) Merr.], sunflower (Helianthus annuus L.), and corn, in Serbia. Currently, acetolactate synthase–inhibiting herbicides, such as the systemic selective sulfonylurea nicosulfuron, are most commonly used for chemical weed control of those species. A better understanding of the impact of nozzle type and adjuvant use on nicosulfuron efficacy can help to improve control of common lambsquarters and johnsongrass and minimize herbicide resistance development. Field trials were conducted in Serbia from 2020 to 2022 to evaluate the impact of two adjuvants (a non-ionic surfactant [NIS] and a mineral fertilizer ammonium sulfate [AMS]) and two nozzle types (drift-reducing nozzles and flat-fan nozzles) on common lambsquarters and johnsongrass control using nicosulfuron. Satisfactory biomass reduction of common lambsquarters (83% to 87%) and johnsongrass (83% to 97%) was achieved after nicosulfuron application. Adding a NIS adjuvant increased the biomass reduction for common lambsquarters (94% to 98%) and johnsongrass (90% to 100%) independently of the nozzle type used. Selection of nozzle type did not show consistent effects on common lambsquarters and johnsongrass control. Nicosulfuron efficacy was increased with NIS adjuvant for both nozzle types compared to nicosulfuron solo for both species, and Extended Range (XR) TeeJet® nozzles on average resulted in a higher efficacy for common lambsquarters compared to Turbo TeeJet® induction. Adding a mineral AMS adjuvant resulted in lower biomass reduction for both nozzle types and weed species (65% to 78% and 61% to 91% for common lambsquarters and johnsongrass, respectively). Corn grain yield was predominantly influenced by annual meteorological conditions and adjuvant type added to nicosulfuron. This research suggests that addition of the non-ionic adjuvant is an essential factor for successful control of common lambsquarters and johnsongrass in corn and enables use of drift-reducing nozzles.

Italian ryegrass is one of the most troublesome weeds worldwide because of the rapid evolution of herbicide resistance in this species. Oregon tall fescue seed production requires high seed purity, demanding good control of Italian ryegrass. The necessity to control herbicide-resistant Italian ryegrass and maintain tall fescue seed purity created interest in new chemical management options. The objectives of this study were to assess the effects of synthetic auxin herbicides on seed viability of Italian ryegrass biotypes and the feasibility of this management strategy for use in tall fescue seed production. Eight treatments of synthetic auxin herbicides were applied to Italian ryegrass and tall fescue at two growth stages (boot and anthesis): dicamba (1.0 and 2.2 kg ae ha−1), 2,4-D (1.1 and 2.2 kg ae ha−1), aminopyralid (0.5 kg ae ha−1), dicamba + 2.4-D (0.8 + 1.1 kg ae ha−1), 2.4-D + clopyralid (1.1 + 0.3 kg ae ha−1), and halauxifen-methyl + florasulam (0.4 kg ae ha−1 + 0.4 kg ai ha−1). Aminopyralid applied at boot and anthesis stages of Italian ryegrass reduced seed viability. Aminopyralid treatments reduced seed viability and weight of Italian ryegrass more than 50% compared to the control. Four biotypes from different locations in western Oregon with different types of herbicide resistance were sprayed, and differences in aminopyralid effect among Italian ryegrass biotypes were documented. Aminopyralid reduced the speed of germination by 1 to 2 d. Aminopyralid treatments had a greater effect when applied at the anthesis stage and had a greater negative impact on tall fescue. Tall fescue plants were more susceptible to aminopyralid, so this management practice is not feasible for tall fescue seed production. Future studies are needed to understand the physiological mechanisms involved in the reduced seed viability and to define an optimum aminopyralid rate for different Italian ryegrass biotypes.

Crop enterprise budgets for eight crops prepared from a sample of 131 farms in the Chaouia region of Settat province, Morocco show that weed management is a component of crop production. Although all farmers used herbicides on small grains, weed control was accomplished primarily with hired and family labor. In general, labor is more plentiful than capital and the per hectare cost of using hired labor is low. The percentage of total cash expenditures assigned to weed management averaged more than 5% in each farm size group. However, there was substantial variability among crops. Average hours spent to manage weeds was nearly constant for the three groups. Barley received the least labor and corn or a food legume the most. Farmers of small farms used more family labor and those of large farms used more hired labor.

Field experiments were conducted to determine the effect of CGA184927 rate, weed growth stage, and tank mixes with various broadleaf herbicides on the control of green foxtail and wild oat in spring wheat. CGA 184927 controlled green foxtail and wild oat equally well when applied at the 2- to 3- or 4- to 5-leaf stages. Green foxtail and wild oat were controlled at similar rates of CGA 184927 but the application rate giving > 90% control ranged from 22 to 90 g/ha over locations and years, indicating that CGA 184927 efficacy is sensitive to environmental conditions. CGA 184927 in tank mixtures was compatible with bromoxynil, clopyralid, and 2,4-D ester. However, tank mixing with metsulfuron or dicamba reduced activity on green foxtail and wild oat. Broadleaf herbicide activity on kochia and redroot pigweed was not reduced when such herbicides were tank-mixed with CGA 184927. Spring wheat tolerated 120 g/ha of CGA 184927. CGA 184927 provides growers with another herbicide option to control green foxtail and wild oat in wheat.

Field experiments were conducted at Belleville, Colby, Hays, Hesston, Garden City, and Manhattan, KS, to determine grain sorghum response to POST application of mesotrione at three application timings. Mesotrione was applied at 52, 105, 157, and 210 g ai/ha in combination with 280 g ai/ha atrazine to grain sorghum at heights of 5 to 8, 15 to 20, and 30 cm, which correspond to early POST (EPOST), mid-POST (MPOST), and late POST (LPOST), respectively. All mesotrione rates caused injury at all application timings. Overall, grain sorghum injury from mesotrione was greatest at 1 wk after treatment (WAT); plants partially recovered from injury by 4 WAT. Mesotrione applied EPOST injured grain sorghum more than when applied at MPOST and LPOST timings. The EPOST application injured grain sorghum 19 to 88%, whereas injury from MPOST and LPOST application was 1 to 66% and 0 to 69%, respectively, depending on rate. Mesotrione injury was least at Belleville and most at the Hesston and Garden City (irrigated) sites regardless of growth stage. Correlation coefficient analyses indicated that observed mesotrione injury symptoms were not well correlated with grain sorghum yield; thus, mesotrione injury to grain sorghum did not influence grain yield. However, initial grain sorghum injury was severe, and this will likely be a major concern to producers.

Alfalfa seed producers have a limited number of herbicide options to manage weed problems. MON-37500 (proposed name sulfosulfuron) is a sulfonylurea herbicide that controls dandelion and quackgrass, two common weeds in alfalfa fields. A study was conducted in two alfalfa fields at Valparaiso and Carrot River, Saskatchewan, Canada, from 1999 to 2001 to evaluate perennial weed control and alfalfa production responses with 0.5×, 1×, and 1.5× label-recommended rates of MON-37500 and also 2,4-DB and hexazinone. MON-37500 applied at the 1× and 1.5× rates at both locations reduced mid-May alfalfa vigor from 100% to between 80 and 90% and increased early-season control of dandelion and quackgrass by about 10 to 40 percentage units, when compared with other herbicide treatments. Improved weed control with 1× and 1.5× MON-37500 rates was sustained into mid-June only at Carrot River and was completely eliminated (100% vigor and 0% weed control), or almost so, by mid-July. MON-37500 did not control Canada thistle. Improved early-season weed control with the 1× MON-37500 rate apparently compensated for the loss of alfalfa vigor at Valparaiso, thus resulting in 27% (57 kg/ha) greater seed yield than with the other herbicide treatments. At Carrot River, hexazinone generally provided levels of weed control similar to MON-37500 but did not injure alfalfa. Consequently, alfalfa yields were highest and the proportion of dead (decaying) seed was least with this treatment. The 0.5× MON-37500 rate often resulted in inferior weed control relative to the 1× and 1.5× rates and never was among the herbicide treatments providing the greatest seed yield. Managing the residual activity of MON-37500 and its negative effect on alfalfa growth, especially at locations with soils having coarse texture and low organic matter content, represents the greatest challenge in making MON-37500 a reliable weed management tool for alfalfa seed producers.

In preliminary field trials, a reduction in grass control was observed when flumetsulam or MON 12037 with and without the safener MON 13900 was applied with metolachlor compared to metolachlor alone. Greenhouse studies were initiated to study potential interactions between acetolactate synthase (ALS)-inhibiting herbicides and metolachlor. Metolachlor at 0.14, 0.28, and 0.56 kg ai/ha was applied alone and in combination with flumetsulam at 0.0073 and 0.015 kg ai/ha and MON 12037 with safener at 0.011 and 0.021 kg ai/ha. Flumetsulam and MON 12037 with safener alone provided 13 to 23% visible barnyardgrass control and metolachlor at 0.14 kg/ha provided 82% control. Combining flumetsulam and MON 12037 with metolachlor did not increase herbicide activity beyond that observed from metolachlor alone, regardless of the parameter evaluated. Combinations of 0.14 kg/ha of metolachlor with 0.011 and 0.021 kg/ha of MON 12037 with safener or 0.015 kg/ha of flumetsulam resulted in antagonism of barnyardgrass according to Colby's multiplicative interactive model. Visible control and plant dry weight were also antagonized when 0.28 kg/ha of metolachlor was applied with 0.021 kg/ha of MON 12037 with safener. Field studies were conducted in corn and soybean to evaluate giant foxtail control from metolachlor alone and in tank mixtures with flumetsulam, chlorimuron and MON 12037 with and without safener. Although isolated incidences of antagonism were noted, there was no consistent effect on grass control when these ALS-inhibiting herbicides were applied in combination with metolachlor in 3 years of field trials.

Triticale is a low input crop, produced in North America primarily for silage for animal feed. Currently, seed growers have few herbicide options for producing certified seed. There is anecdotal evidence that triticale tolerates many of the same herbicides as wheat. In 2004 and 2005, the tolerance of three spring triticale varieties (AC Alta, AC Ultima, and Pronghorn) was tested with four herbicides registered for wheat: florasulam + MCPA ester, clodinafop-propargyl, thifensulfuron-methyl/tribenuron-methyl, and sulfosulfuron-methyl + 2,4-D ester. Herbicides were applied at the label rate (1×) for wheat and twice (2×) that rate. Crop injury, plant height, biomass, and seed yields were quantified. Neither florasulam + MCPA ester, clodinafop-propargyl, nor thifensulfuron-methyl/tribenuron-methyl at 1× or 2× use rates significantly injured triticale. Sulfosulfuron-methyl + 2,4-D ester reduced triticale height at the 1× and 2× rates, as well as reduced biomass and yield at the 2× rate. Florasulam + MCPA ester, clodinafop-propargyl, and thifensulfuron-methyl/tribenuron-methyl do not cause significant crop injury and can be used for weed control in spring triticale, but sulfosulfuron-methyl + 2,4-D ester is not recommended for use in triticale.

Broad- host-range pathogens are appealing as candidates for commercial development as bioherbicides because of the wider market potential of a product that is effective against a range of weeds. But when these pathogens are able to spread in space (or time), a risk analysis is necessary. Here we test the hypothesis that a safety zone around a bioherbicide application site is adequate so long as it is wide enough to ensure that dispersing inoculum has diluted sufficiently that the density of inoculum occurring naturally in a susceptible crop is no more than doubled by the influx of bioherbicide spores. To this end the plant disease–pathogen inoculum density relationship using data from nine published experiments was modeled using the logistic equation. This revealed that a doubling of the natural spore density of a plant pathogen in the range of 103.4 to 106.7 spores/ml may generally be expected to result in unacceptable increases in disease in a susceptible crop. A doubling outside this range (< 103.4 or > 106.7) is less likely to do so. Therefore when the natural density of inoculum in a crop's environment occurs outside this range, an “acceptable” safety zone for the pathogen's use as a bioherbicide can in most cases be defined by the 1 : 1 ratio of added : natural inoculum. However, if a more “risk averse” safety zone is desired, it can be defined using a 1 : 10 ratio of added : natural inoculum.

Field experiments were conducted to evaluate postplant crop residue, green and yellow foxtail control, and wheat grain yield after fall application of trifluralin granules in undisturbed small grain stubble. Levels of postplant residue were at least 48% cover (line transect method) and 2750 kg/ha of aboveground dry matter where herbicide granules were left unincorporated or were incorporated with conservation-till methods, including an undercutter, rotary hoe, or undercutter followed by a rotary hoe. Trifluralin at 0.56 kg/ha applied as granules in mid October in untilled stubble and incorporated with conservation-till methods controlled foxtail 81 to 88%, with control appearing slightly lower when granules were not incorporated. The 81 to 88% foxtail control in conservation-till treatments was comparable to control achieved with trifluralin at 0.56 kg/ha applied in mid October on conventionally-tilled soil and incorporated by a field cultivator. Foxtail control improved somewhat as trifluralin rate was increased to 0.84 and 1.12 kg/ha in conservation-till treatments. Slight wheat stand reductions at 1.12 kg/ha of trifluralin did not appear to reduce wheat yield. Fall application of trifluralin granules in these high-residue conditions apparently minimizes herbicide losses by photodecomposition and volatility, thereby facilitating good trifluralin efficacy the following season.

Flame cultivation (FC) uses brief exposures of high temperature to control weeds. Three sites in southeastern Massachusetts with dewberry present were studied over a 2-yr period to determine if seasonal timing and frequency of exposure to FC would reduce dewberry stem length and biomass, both in the year of and the year following treatment, and also to evaluate whether FC treatments altered the ratio (sugar : starch) of nonstructural carbohydrates (NSC) in dewberry roots. Dewberry plants were treated with a 9-s exposure to an open-flame hand-held torch at seven different timing regimes (one application in June, July, or August or two applications in June/July, June/August, and July/August, or nontreated). After 1 yr, all treatments showed reduced aboveground dewberry biomass compared to nontreated plots. The timing and frequency of FC treatments were not significant when the weed was growing amongst cranberry vines, but were significant when weeds were treated in the absence of cranberry. Exposure to FC did not affect the ratio of NSC in roots in the year after treatment, indicating that the relative amounts allocated to each type of storage carbohydrate did not differ from nontreated plants, even though the overall amount allocated to root biomass was reduced.

A major hindrance to establishment of successful complementary forage systems that include warm-season perennial grasses and clovers is tolerance of the latter to herbicides available for weed control. Field experiments were conducted in 2013 at two locations in northeast Louisiana to evaluate simulated residual rate effects of fluroxypyr plus triclopyr and 2,4-D plus picloram applied at 0, 0.25, 0.38, and 0.5× use rates immediately after fall planting of ball, white, crimson, and red clover. For all clovers, when averaged across herbicide rates, plant population 161/171 d after planting (DAP), ground cover, and height 184/196 DAP were equivalent for fluroxypyr plus triclopyr and the nontreated control and greater than 2,4-D plus picloram. Averaged across clovers, plant height after all rates of fluroxypyr plus triclopyr was equivalent to the nontreated control (14.2 to 14.3 vs. 15.3 cm) and greater than 2,4-D plus picloram. Compared with the nontreated control, 2,4-D plus picloram at 25, 38, and 50% of the normal use rates reduced height 58, 76, and 85%, respectively. When averaged across clover species, yield for fluroxypyr plus triclopyr at all rates was equivalent to the nontreated control (2,624 to 2,840 vs. 2,812 kg ha−1). Compared with the nontreated control, 2,4-D plus picloram at the 0.25, 0.38, and 0.50× use rates reduced yield 65, 89, and 99%, respectively.

Pendimethalin control failures on tall morningglory are critical shortcomings in weed-control programs for chile pepper in New Mexico. Using weed seedbank augmentation, we conducted a field study to (1) determine if pendimethalin control of tall morningglory is affected by tall morningglory seedbank density, and (2) identify weed community factors that influence labor for removing the tall morningglory plants that escape pendimethalin. The field study was complemented with a growth chamber study conducted to clarify the effects of pendimethalin rate on the putative association between tall morningglory seedbank density and pendimethalin control outcomes. Under field conditions and after square-root transformation of the dependent variable, the effects of seedbank density on seedling escape density were described with natural logarithmic functions. Although pendimethalin control of tall morningglory decreased with increasing seedbank density, seedbank additions increased labor requirements for removing tall morningglory at only a site-year characterized by low population densities in the indigenous weed community. In growth chambers, increasing pendimethalin rate negatively influenced the effects of increasing seedbank density on pendimethalin control failures. This study shows that pendimethalin control of tall morningglory is reduced when seedbank densities of this species are high. Knowledge of seedbank density effects on specific control outcomes may influence grower attitudes on management strategies that target weed seedbanks.

Greenhouse studies were conducted in Raleigh, NC to determine Carolina redroot control by selected PRE and POST herbicides labeled for blueberries. Paraquat, glufosinate, glyphosate, and flumioxazin provided some Carolina redroot shoot control 7 d after POST application (DAPOST) ranging from 48 to 74%. Control 25 DAPOST was greatest for hexazinone at 2.2 kg ai ha−1 (90%) followed by glufosinate with 56% control and paraquat and terbacil each with 53% control. Control for most treatments declined between 25 and 63 DAPOST with the exception of glyphosate, which increased to 64%. Carolina redroot shoots per pot were reduced by terbacil, hexazinone at 2.2 kg ha−1, and glyphosate compared with the nontreated check 63 DAPOST. Control of Carolina redroot roots and rhizomes 63 DAPOST ranged from 7 to 68%, with the greatest control provided by terbacil (68%) and hexazinone at 2.2 kg ha−1 (64%). Terbacil and hexazinone at 2.2 kg ha−1 were the only treatments that reduced both shoot and root/rhizome dry weight compared with the nontreated check.