Japanese stiltgrass is one of the most troublesome invasive weed species in the eastern United States. Strategies for Japanese stiltgrass control in managed lawns are limited since most previous research was conducted in forest understories or golf course natural areas. Eight field experiments were conducted in Virginia from 2014 to 2019 to evaluate the response of Kentucky bluegrass, tall fescue, and Japanese stiltgrass to selective herbicides traditionally marketed for cool-season turfgrass. Only mesotrione-containing treatments transiently injured tall fescue 15 to 25% at 2 wk after treatment (WAT). Fenoxaprop at 35 g ha-1 or higher rates controlled Japanese stiltgrass ≥ 90%, reduced relative cover to <15% compared to nontreated and shoot density to ≤ 6 shoots m-2, respectively, at 8 WAT. Sequential application of topramezone at 3-wk intervals at 27 g ha-1, single application of topramezone at 54 g ha-1 alone or with triclopyr controlled Japanese stiltgrass ≥ 80% and reduced relative weed cover and shoot density to ≤ 22% and < 35 shoots m-2, respectively. Fenoxaprop at 0.25 of the labeled rate for annual grass control in lawns and topramezone-based programs selectively controlled Japanese stiltgrass without injuring tall fescue. Fluazifop at 53 g ha-1 injured Kentucky bluegrass 25% and reduced digitally assessed turf cover by 20% at 4 WAT, but turfgrass recovered by 6 WAT. Reduced rates of fluazifop controlled Japanese stiltgrass 85% and reduced weed shoot density to < 20 shoots m-2 and relative cover to < 20% at 8 WAT. A premix of dicamba, fenoxaprop, and fluroxypyr did not injure Kentucky bluegrass but controlled Japanese stiltgrass ≥ 92% and reduced the relative weed cover and shoot density to ≤ 7% and ≤ 5 shoots m-2, respectively, at 8 WAT. Our research provides herbicide options to practitioners to manage Japanese stiltgrass in Kentucky bluegrass and tall fescue lawns.

Water hyacinth is a highly invasive, aquatic species in the southern US that requires intensive management through frequent herbicide applications to minimize harmful impacts. Quantifying management success in large-scale operations is challenging with traditional survey methods, which rely on boat-based teams and can be time-consuming and labor-intensive. In contrast, unmanned aerial systems allow a single operator to survey a waterbody more efficiently and rapidly, enhancing both coverage and data collection. Therefore, the objective of this research was to develop remote sensing techniques to assess herbicide efficacy for water hyacinth control in an outdoor mesocosm study. Experiments were conducted in spring and summer 2023 to compare and correlate data from visual evaluations of herbicide efficacy against nine vegetation indices (VIs) derived from unmanned aerial system (UAS)-based red-green-blue (RGB) imagery. Penoxsulam, carfentrazone, diquat, 2,4-D, florpyrauxifen-benzyl, and glyphosate were applied at two rates, and experimental units were evaluated for six weeks. The Carotenoid Reflectance Index (CRI) had the highest Spearman’s correlation coefficient with visually evaluated efficacy for 2,4-D, diquat, and florpyrauxifen benzyl (> -0.77). The Visible Atmospherically Resistance Index (VARI) had the highest correlation for carfentrazone and penoxsulam treatments (> -0.70), and the EXGR Excess Greenness Minus Redness Index had the highest correlation for glyphosate treatments (> -0.83). CRI had the highest correlation coefficient with the most herbicide treatments, and it was the only VI tested that did not include the red band. These vegetation indices were satisfactory predictors of mid-range visually evaluated herbicide efficacy values but were poorly correlated with extremely low and high values, corresponding to non-treated and necrotic plants. Future research should focus on applying findings to real-world (non-experimental) field conditions and testing imagery with spectral bands beyond the visible range.

Herbicide-resistant weeds demand particular attention in the selection of management strategies, considering the characteristics and fitness differences between susceptible and resistant plants. This study aimed to analyze two heterogeneous junglerice populations, glyphosate-susceptible (EC-S) and glyphosate-resistant (EC-R), derived from field-collected seeds, to quantify the productivity of EC-S and EC-R, to analyze the impact of soybean plants, and to evaluate density dependence. Experiments were conducted in a growth chamber using plastic pots, combining three factors: junglerice density (2, 4, and 8 plants pot⁻¹), the proportion of EC-S and EC-R (100% EC-S, 50% EC-S:50% EC-R, 100% EC-R), and soybean density (0 and 1 plant pot⁻¹). One-leaf junglerice seedling and soybean seeds were planted in plastic pots. After 65 days, plant height (PLH), total number of tillers (TIL), seed number (SEN), and seed weight (SEW) per plant, weight of 100 seeds (HSW), and aboveground dry matter (ADM) were measured. The variables measured were primarily affected by junglerice density and the presence of soybean. Vegetative and reproductive structures of EC-S and EC-R exhibited strongly density-dependent patterns. One soybean plant increased (p<0.05) junglerice productivity at low densities but had no effect at high densities (8 plants pot⁻¹). Mostly EC-S and EC-R showed the same competitive ability. However, EC-S presented a higher index of competitive ability than EC-R in SEN and SEW at lower densities with a soybean plant. A resource complementarity (RYT∼1) between EC-S and EC-R was observed (p<0.05), regardless of the presence of the crop. These results demonstrate that, even in the absence of glyphosate, fitness differences favor heterogeneous resistant populations. This highlights the inherent adaptive advantage of resistant populations and, considering the extensive reliance on glyphosate in current production systems underscores the urgent need for integrated weed management strategies to mitigate the evolution and spread of resistant populations.

Chickpea provides significant diversification benefits for semi-arid cropping systems. However, their slow emergence and open canopy growth habit make them poor competitors against rapidly growing weeds during the early season. In 2022 and 2023, field experiments were conducted at two sites, the Montana State University (MSU) Southern Agricultural Research Center, Huntley, MT, and the MSU Post Agronomy Farm, Bozeman, MT, to evaluate broadleaf weed management by integrating planting date and fall-applied soil-active herbicides in chickpea. Application of dimethenamid at 950 g ai ha-1 + pendimethalin at 1.68 kg ai ha-1, and carfentrazone + sulfentrazone at 238 g ai ha-1 resulted in better protection of yield against weeds and provided longer residual activity for control of kochia, redroot pigweed, and common mallow by reducing weed density to 10 - 20 plants m-2 compared to 50 - 70 plants m-2 in untreated check. Pyridate applied POST (700 g ai ha-1) was required in the above-mentioned treatments to eliminate escaped weeds. Early planting provided an additional biomass reduction compared to late planting due to the crop emergence before or around the same time as the weeds. There was no impact of planting date on weed density and grain yield in plots with dimethenamid + pendimethalin and carfentrazone + sulfentrazone, suggesting that these herbicides can extend the planting date window. These herbicide programs and early planting can be integrated with other weed management tactics for additional weed management options in chickpea.

Palmer amaranth, a competitive weed in cotton and soybeans, poses challenges due to its rapid growth, high fertility, and herbicide resistance. Effective management strategies targeting sex ratios could reduce seed production by female plants. Protoporphyrinogen oxidase (PPO-) inhibiting herbicides play a role in the evolving resistance of Amaranthus spp. in the Midwestern US. These herbicides may also affect the male-to-female ratio of Palmer amaranth. A two-year field experiment (2015 and 2016) was conducted in a soybean field in Collinsville, Illinois, evaluating various preemergence and postemergence PPO-inhibiting herbicide treatments. Untreated Palmer amaranth populations exhibited a bias towards females. Pre-emergence application of sulfentrazone and flumioxazin effectively reduced Palmer amaranth density (1.66 plants m-2) throughout the season, while post-emergence applications of fomesafen and lactofen provided limited control (27 and 31 plants m-2). Early-season mortality was high (96 %) among Palmer amaranth seedlings, especially with pyroxasulfone+fluthiacet-methyl treatment. Fomesafen increased female biomass (28.8 %) while reducing male biomass compared to non-treated control. In 2015, pyroxasulfone+fluthiacet-methyl and acetochlor altered the male-to-female sex ratio compared to the non-treated control, with pyroxasulfone+fluthiacet-methyl reducing the proportion of females (-0.11 M:F) and acetochlor slightly increasing the proportion of males (0.03 M:F), though not different from a 1:1 ratio. In 2016, pendimethalin and flumioxazin-2 resulted in a strong female-biased sex ratio, with an almost exclusively female population. In both years, the non-treated control plots (-0.58 and -0.55 M:F) maintained a naturally female-biased sex ratio, deviating significantly from a 1:1 ratio. These findings suggest that specific herbicide treatments can alter the sex ratio.. Understanding sex determination in Palmer amaranth holds promise for developing more effective control strategies in the future.

Recently a premix of tolpyralate and bromoxynil was registered in the USA and Canada by Corteva Agriscience for weed control in cereals. Limited information exists on weed control efficacy and crop safety with this new herbicide pre-mixture. Greenhouse trials were conducted for two years to test the efficacy of tolpyralate and bromoxynil combinations on 14 broadleaf and 4 grass weeds and crop safety in wheat and barley. Four combinations of tolpyralate and bromoxynil at 1:10 ratio (3.75 + 37.5, 7.5+ 75, 11.25 + 112.5, and 15 + 150 g ai ha-1) as a tank-mix and premix were tested. Stand-alone treatments of tolpyralate and bromoxynil were also included in this study. The lowest tested rate of tolpyralate (3.75 g ha-1) provided 10 to 98% and 27 to 77% control of broadleaf and grass weeds, respectively. Bromoxynil at the lowest tested rate (37.5 g ha-1) provided 16 to 80% and 0 to 30% control of broadleaf and grass weeds, respectively. Tank-mixing these two herbicides at the same rates had improved broadleaf (60 to 100%) and grass (45 to 94%) weed control. The minimum recommended field use rate of tolpyralate +bromoxynil (15 + 150 g ha-1) controlled all the broadleaf weeds >95%. This combination also controlled green foxtail, barnyardgrass and large crabgrass >90%. Additive or synergistic effect between the two herbicides was observed on several broadleaf and grass weed species. Among all the tested weeds, greater synergistic effect was observed on kochia, chickweed, wild mustard, corn poppy, barnyardgrass, green foxtail, and fall panicum. The premix of the two herbicides provided similar broadleaf control, but better grass weed control compared to the tank-mix combinations. Premix was safe on wheat and barley.

Clethodim is an important herbicide for managing Texas panicum. However, its efficacy is influenced by the weed size and environmental stress during application. Therefore, field and greenhouse studies were conducted in 2023 and 2024 to evaluate clethodim efficacy on various Texas panicum sizes. Clethodim was applied at Texas panicum sizes ranging from 5 cm to 60 cm. A sequential application was applied two weeks after the initial treatment for larger weed sizes (15 to 60 cm). In separate field and greenhouse studies, non-ionic surfactant (NIS), crop oil concentrate (COC), methylated seed oil (MSO), COC + ammonium sulfate (AMS), and MSO + AMS adjuvants were mixed with clethodim to determine efficacy on 10-15 cm and 20-30 cm Texas panicum. In the weed size study, sequential applications of clethodim increased Texas panicum control compared to a single application. At the 10-15 cm growth stage, a single application provided 90% Texas panicum control, whereas the sequential treatment improved control from 76% to 91% at the 15-20 cm growth stage. However, clethodim efficacy declined as Texas panicum size increased across single and sequential treatments. In the adjuvant studies, clethodim plus COC, COC+AMS, or MSO+AMS provided 91%, 93%, and 90% control at the 10-15 cm growth stage, respectively; however, efficacy decreased for 20-30 cm Texas panicum. Texas panicum efficacy was higher for clethodim plus MSO+AMS than clethodim plus MSO; however, AMS did not increase clethodim + COC efficacy. Overall, Texas panicum control with clethodim was most effective when weed height was 15 cm or less. A sequential application of clethodim was required for larger Texas panicum (>15 cm). Clethodim plus COC or MSO+AMS provided the highest control of Texas panicum. This study demonstrated that successful Texas panicum management depends on applying clethodim at the optimum size and selecting the appropriate oil-based adjuvant especially at larger Texas panicum sizes.

Purple witch-weed is a parasitic plant that significantly impacts sorghum yields in semi-arid regions. It also affects crops like corn, millets, and rice. Developing purple witch-weed-resistant sorghum varieties is essential for integrated purple witch-weed management. This study evaluated the response of 48 sorghum genotypes to purple witch-weed under both pot and field conditions. Resistant varieties (Berhan and Framida) and susceptible varieties (Assosa-1, Adukara, and/or ETSL102967) were used as controls. The findings revealed substantial variability among the sorghum landraces in their response to purple witch-weed. Early maturing genotypes exhibited lower purple witch-weed densities, while late maturing ones were more susceptible. Notably, the ETSL102969 landrace showed strong resistance, comparable to the resistant variety Berhan. Additionally, the ETSL102970 landrace demonstrated superior resistance compared to Framida. Based on these results, ETSL102969 and ETSL102970 are recommended as valuable sources of resistance for breeding programs aimed at improving sorghum resistance against purple witch-weed in Ethiopia.

Auxinic herbicides are the second most used in Brazil, often combined with glyphosate in pre-plant burndowns management. However, their efficacy against Benghal dayflower at advanced growth stages remains poorly understood. Two field experiments were conducted in 2021 and 2022 on no-till fields naturally infested with Benghal dayflower at an advanced growth stage (∼50 cm height, 100% soil coverage) to evaluated the control efficacy of 2,4-D at 966 g ae ha-1, triclopyr at 720 g ae ha-1, fluroxypyr at 400 g ae ha-1 and dicamba at 720 g ae ha-1, combined or not with glyphosate (1,550 g ae ha-1). Dicamba was also tested at rates from 288 to 1,008 g ae ha⁻¹. Results indicate Benghal dayflower exhibits variable responses to auxin herbicides, influenced by both chemical family and the herbicide molecule. None of the treatments provided complete control at 8 wk after application (WAA). The highest visible control (∼77%) and dry mass reduction (∼57%) were provided by triclopyr (isolated or combined with glyphosate) and 2,4-D (combined with glyphosate), followed by fluroxypyr (isolated or combined with glyphosate) and 2,4-D (isolated), providing ∼69% visible control and 54% dry mass reduction. Even when statistical differences were detected by adding glyphosate to auxin herbicides, these differences were not sufficient to characterize a synergistic effect or improve control consistency. Dicamba (isolated or combined with glyphosate) provided the lowest control (∼54%) and dry mass reduction (∼30%). Additionally, dicamba doses up to 1008 g ae ha⁻¹ did not provide complete control (∼60% visible control and 51% dry mass reduction), suggesting that dicamba limitations cannot be mitigated through dose increase. By highlighting the challenges in controlling Benghal dayflower at advanced growth stages, these results emphasize the importance of early-stage weed control and the need to carefully assess which auxin herbicides to use and when glyphosate mixtures are necessary.

Wild oat is a significant weed of cropping systems in the Canadian Prairies. Wild oat resistance to herbicides has increased interest in non-chemical management strategies. Harvest weed seed control techniques such as impact mills or chaff collection have been of interest in Prairie crops, with wild oat identified as a key target. To evaluate impacts of crop rotation maturity, harvest management and harvest weed seed control on wild oat, a study was conducted from 2016-2018 at four locations in the Canadian Prairies. Two-year crop rotations with either early, normal, or late-maturity crops were implemented before barley was seeded across all rotations in the final year. In addition, a second factor of harvest management (swathing or straight cut) was included in the study. Chaff collection was used in this study in an attempt to quantify wild oat seeds that were targetable by harvest weed seed control techniques. The hypothesis was that earlier maturing crops would result in increased wild oat capture at harvest and, therefore, lower wild oat populations. Wild oat density and wild oat biomass were lowest in the early maturing rotations. In addition, wild oat biomass was lower in swathed crops than in straight-cut crops. Wild oat seedbank levels reflected a similar trend with the lowest densities in early maturing rotation, then the normal maturity rotation and the late maturing rotation had the highest seedbank densities. Wild oat densities increased in all crop rotations; however, only harvest weed seed control and crop rotation were implemented as control measures. Wild oat numbers in the chaff were not reflective of the earliness of harvest. Crop yields suggest that competitive winter wheat stands contributed to the success of the early maturing rotations compared to other treatments. Early maturing rotations resulted in reduced wild oat populations, likely through a combination of crop competitiveness and rotational diversity, and harvest weed seed control impact in earlier maturing crops.

Galium aparine L. var. echinospermum (Wallr.) Cuf., an annual or winter annual broadleaf weed in the Rubiaceae family, has become troublesome due to its herbicide resistance in the wheat fields of the Huang-Huai-Hai region in China. Four cleavers populations (JS-15, SD-10, JS-22, and AH-20) were collected from the wheat fields of Jiangsu, Shandong, and Anhui Province, where florasulam control was absent. This study identified the herbicide resistance patterns and investigated the mechanism underlying the florasulam resistance. The whole-plant dose-response experiments revealed a notable variation in the degree of resistance exhibited by three specific populations towards florasulam, in comparison to the most sensitive populations (S and AH-9), with the highest resistance index reaching 841.4. Acetolactate Synthase gene-sequencing assay found that R plants from JS-15, JS-22, and AH-20 had a Trp-574-Leu mutation, while no known ALS resistance mutations were discovered in SD-10 plants. In vitro ALS enzyme activity assays also indicated that the extractable ALS from the resistant plants of JS-15, JS-22, and AH-20 was greatly resistant to florasulam relative to that of the susceptible. Additionally, according to the resistance rating system, all resistant populations were susceptible to Carfentrazone-ethyl + MCPA-Na and Bipyrazone + Fluroxypyr-methyl. AH-20, JS-15, and JS-22 exhibited resistance to selected ALS, 4-hydroxyphenylpyruvate dioxygenase, and photosystem Ⅱ complex inhibitors, demonstrating RR and RRR resistance profiles, whereas AH-9 displayed S-sensitivity to virtually all tested agents. SD-10, on the other hand, showed RR and RRR resistance to HPPD and PSII inhibitors, but exhibited S-sensitivity specifically to tribenuron-methyl. These findings indicate that a target site-based mechanism drives the resistance to the ALS inhibitor florasulam in cleavers populations, but NTSR resistance may have also contributed (was not investigated). Other herbicides with different sites of action were tested and were active against cleavers.

Branched broomrape management is of increasing concern to California processing tomato growers. Field research was conducted in 2023 and 2024 to evaluate various application timings of chemigated rimsulfuron alone, preplant incorporated (PPI) sulfosulfuron paired with chemigated rimsulfuron, as well as foliar maleic hydrazide alone and paired with PPI sulfosulfuron and chemigated rimsulfuron. In 2023, all treatments with 70 g ai ha-1 rimsulfuron, alone or paired with PPI sulfosulfuron, reduced broomrape emergence 77 to 92% compared to the nontreated control. In 2024, broomrape pressure was higher, and all rimsulfuron treatments reduced broomrape emergence 68 to 86% compared to the control. In both years, five applications of foliar maleic hydrazide reduced broomrape emergence through at least midseason. The 2024 experiment included a combination treatment of PPI sulfosulfuron, chemigated rimsulfuron, and foliar maleic hydrazide, which resulted in fewer than four broomrape clusters per plot. In a 2024 grower-scale demonstration trial, two application regimes totaling 70 g ai ha-1 of chemigated rimsulfuron reduced broomrape emergence 83 to 89% compared to the control. Overall, chemigated rimsulfuron applied at various timings and rates totaling 70 g ai ha-1 reduced broomrape emergence by two-thirds or more compared to the nontreated plots. No crop injury was observed in trials with rimsulfuron, sulfosulfuron, or maleic hydrazide treatments in small plot trials or with rimsulfuron in the grower-scale demonstration trial. Under a recently approved 24(c) Special Local Need label, California growers can use three applications of rimsulfuron applied via chemigation to suppress broomrape in known infested fields or to reduce the risk of broomrape establishment in fields of concern for this quarantine pest. Promising results from sulfosulfuron and maleic hydrazide suggest that registering additional herbicides could help develop even more robust branched broomrape management programs.

Indaziflam was evaluated in Connecticut and Tennessee, USA, for weed control and safety of container-grown ornamental plants. Indaziflam was applied at 49, 98, or 196 g ha-1 to container-grown ornamental plants on an outdoor gravel pad and preemergence or early postemergence to weeds in greenhouse. Ornamental plants were treated twice annually in 2020 and 2021 in Connecticut, and in 2019 and 2020 in Tennessee, with approximately six weeks between applications. Chinese pyramid juniper, common juniper, eastern hemlock, eastern white pine, and Norway spruce in Connecticut, USA, and 'Andorra Compacta’ creeping juniper and 'Black Dragon’ Japanese cedar, ‘Blue Rug’ creeping juniper, and ‘Blue Pfitzer’ Chinese pyramid juniper in Tennessee, USA, were not injured with indaziflam regardless of rate applied. Preemergence application of indaziflam reduced densities of creeping woodsorrel, hairy bittercress, giant foxtail, and large crabgrass 72 to 100%, depending upon the indaziflam rate applied, by 28 d after treatment (DAT). When applied early postemergence, indaziflam provided 97 to 99% control of creeping woodsorrel (1- to 2-leaf), fringed willowherb (4- to 6-leaf), hairy bittercress (cotyledon to 1-leaf), and mouse-ear chickweed (2- to 4-leaf) by 28 DAT. Compared with the nontreated control, the total fresh shoot biomass reduction was 86 to 100% and 78 to 100% following preemergence or postemergence applications. Indaziflam offers a new site-of-action with excellent safety and weed control in the tested ornamental plants.

New technologies in grain sorghum allow for the use of multiple acetyl CoA carboxylase- (ACCase) or acetolactate synthase- (ALS) inhibiting herbicides for johnsongrass control. With the growing issue of herbicide resistance, producers need to understand which herbicides will successfully control johnsongrass accessions. To determine the efficacy of herbicides recently registered or ones with potential to become available for use in grain sorghum, johnsongrass seeds were collected from 2017 to 2021 in Arkansas, Kansas, Texas, and Oklahoma and were screened for sensitivity to fluazifop, quizalofop, nicosulfuron, and imazamox. Additionally, glyphosate sensitivity was evaluated because of its use before planting or postharvest. Quizalofop resulted in 100% mortality of all johnsongrass accessions. Of the johnsongrass accessions evaluated, 89% were completely controlled with glyphosate. The ALS inhibitors nicosulfuron and imazamox resulted in 100% mortality of all Oklahoma accessions, but failures occurred on samples from other states. One accession from Kansas, 12 from Texas, and eight from Arkansas were found to have reduced sensitivity to nicosulfuron and imazamox. If producers plan to plant grain sorghum in areas with johnsongrass populations, an ACCase-inhibitor herbicide will most likely provide effective control. Imazamox and nicosulfuron, in conjunction with the appropriate trait, can be utilized in areas with sensitive johnsongrass populations or where other sensitive grass species are present.