Herbicide-resistant weeds are fast becoming a substantial global problem, causing significant crop losses and food insecurity. Late detection of resistant weeds leads to increasing economic losses. Traditionally, genetic sequencing and herbicide dose-response studies are used to detect herbicide-resistant weeds, but these are expensive and slow processes. To address this problem, an artificial intelligence (AI)-based herbicide-resistant weed identifier program (HRIP) was developed to quickly and accurately distinguish common chickweed plants that are resistant to acetolactate synthase (ALS) inhibitor herbicides and those that are susceptible to ALS inhibitors. A regular camera was converted to capture light wavelengths from 300 to 1,100 nm. Full-spectrum images from a 2-yr experiment were used to develop a hyperparameter-tuned convolutional neural network model using a “train from scratch” approach. This novel approach exploits the subtle differences in the spectral signature of ALS inhibitor-resistant and ALS inhibitor-susceptible common chickweed plants as they react differently to the ALS-inhibiting herbicide treatments. The HRIP was able to identify ALS-inhibitor–resistant common chickweed as early as 72 h after treatment at an accuracy of 88%. It has broad applicability due to its ability to distinguish common chickweed plants that are resistant to ALS-inhibitor herbicides from those that are susceptible to becoming resistant to them regardless of the type of ALS herbicide or dose used. Using tools such as the HRIP will allow farmers to make timely interventions to prevent the herbicide-escape plants from completing their life cycle and adding to the weed seedbank.

Redweed is a tropical, erect branched herb, and one of the predominant broadleaf weeds affecting upland crops in the Onattukara Sandy Plains of Kerala, India. Experiments were conducted in a screenhouse in Thiruvananthapuram, Kerala, India, to determine the effects of seed burial depth and seed scarification on emergence indices and growth attributes of redweed. Scarification stimulated emergence and resulted in greater values for emergence indices and seedling parameters. The seedling emergence of redweed was influenced by seed burial depth. Shallow seed burial (2 cm) of scarified and non-scarified seeds resulted in greater seedling length (70 cm and 58 cm, respectively), seedling biomass (0.72 g and 0.48 g, respectively), emergence percentage (60% and 32%, respectively), and greater values for other emergence indices. As the depth of seed burial increased from 2 cm, emergence and seedling biomass decreased, exhibiting lower values for the emergence indices. Correlation and regression studies revealed that seed burial depth of scarified and non-scarified seeds greater than 2 cm had a negative effect on seedling emergence and biomass of redweed. Weed biology studies indicated that redweed displayed notable consistency in its phenological traits, regardless of the location where the seeds were collected, as little ecotype variability was observed. Emergence occurred in 6 d, 50% flowering in 44 d, capsule formation in 56 d, and maturity in 76 d. On average, a single plant produced 277 seeds and had a 100-seed weight of 0.31 g. A stale seedbed with shallow tillage or deep plowing to a depth of 10 cm before sowing can be adopted to reduce the infestation of redweed.

Cotton producers need residual herbicides that can safely and practically be applied postemergence. Herbicide-coated fertilizers could allow for simultaneous application of residual herbicides and a bulk fertilizer blend. Therefore, a study was conducted in 2022 and 2023 in Fayetteville, AR, to evaluate cotton tolerance to 12 herbicide treatments coated onto a fertilizer blend and applied over cotton. Herbicides and rates evaluated included diuron at 840 g ai ha−1, florpyrauxifen-benzyl at 29 g ai ha−1, flumioxazin at 105 g ai ha−1, flumioxazin + pyroxasulfone at 70 + 90 g ai ha−1, fluridone at 168 g ai ha−1, fluometuron at 840 g ai ha−1, fomesafen at 280 g ai ha−1, pyroxasulfone at 128 g ai ha−1, saflufenacil at 66 g ai ha−1, saflufenacil + dimethenamid-P at 25 + 219 g ai ha−1, saflufenacil + pyroxasulfone at 44 + 91 g ai ha−1, and S-metolachlor at 1,388 g ai ha−1. In both years, fluridone, fluometuron, diuron, and S-metolachlor caused less than 10% injury at 7 d after treatment (DAT). Higher injury levels were observed in 2022 (19% to 30%) compared with 2023 (4% to 12%) for flumioxazin, fomesafen, saflufenacil, saflufenacil plus dimethenamid-P, and saflufenacil + pyroxasulfone. The elevated injury in one of two years was attributed to the presence of dew when the herbicide-coated fertilizer was applied. The initial injury was transient, as the cotton generally had recovered by 28 DAT for all herbicides. No differences in seed cotton yield or groundcover among the herbicide treatments occurred either year. These results highlight the potential of using several postemergence-applied, residual herbicides coated onto fertilizer that are not currently registered for over-the-top use in cotton.

Off-target herbicide drift away from rice is historically a concern in California, where susceptible crops such as orchards and vineyards are nearby. Tetflupyrolimet is a potent inhibitor of dihydroorotate dehydrogenase that provides excellent grass weed control in rice cropping systems. In efforts to steward tetflupyrolimet before its registration in California, this research was conducted to compare the onset of foliar symptoms from tetflupyrolimet applications onto almond, grapevine, peach, pistachio, plum, and walnut. Tetflupyrolimet was applied to these tree and vine crops at fractional rates of 1/200×, 1/100×, 1/33×, and 1/10× of the 125 g ai ha–1 recommended use rate on rice. Almond, pistachio, and walnut trees also received 1× of the use rate. Tetflupyrolimet treatments were applied on one side of 3- to 4-yr-old almond, peach, pistachio, plum, and walnut trees, and on one side of 25- to 26-yr-old grapevines in 2022 and 2023. Visible injury ratings were carried out weekly to assess symptomology throughout the growing seasons and at leaf-out the following springs. Tree trunk diameter was recorded before and after herbicide applications. No injury was observed to any tested crops, regardless of the tetflupyrolimet application rate. In all orchard crops, tree trunk diameter was not affected by tetflupyrolimet treatments. Likewise, grape yield was not reduced even at the 1/10× tetflupyrolimet fractional rate. Since no injury symptoms were recorded, this research suggests that tetflupyrolimet can be safely used on nearby rice fields and might be a target for future registration consideration for use on orchard and vineyard crops.

Multiple herbicide classes–resistant (MHCR) kochia poses a serious concern for producers in the Central Great Plains, including western Kansas. Greenhouse and field experiments were conducted at Kansas State University Research and Extension Centers near Hays and Garden City, KS, to evaluate pyridate-based postemergence herbicide mixtures for controlling MHCR kochia. One previously confirmed MHCR population (resistant to atrazine, glyphosate, dicamba, and fluroxypyr) and a susceptible (SUS) kochia population were tested in a greenhouse study. The kochia population at Hays field site was resistant to atrazine, dicamba, and glyphosate, whereas the kochia population at the Garden City site was resistant to atrazine and glyphosate. Colby’s analysis revealed synergistic interactions when pyridate was mixed with atrazine, dicamba, dichlorprop-p, fluroxypyr, glyphosate, or halauxifen/fluroxypyr and resulted in ≥94% control and shoot dry-biomass reduction of MHCR kochia in a greenhouse study. Similarly, synergistic interactions were observed for MHCR kochia control in fallow field studies at both sites when pyridate was mixed with glyphosate or atrazine. Kochia control was increased from 26% to 90% with the application of glyphosate + pyridate and from 28% to 95% with atrazine + pyridate at both sites as compared to separate applications of glyphosate or atrazine. This is the first report for such a strong synergistic effect for both glyphosate and atrazine mixtures with pyridate on a weed resistant to both. All other pyridate-based herbicide mixtures showed an additive interaction and resulted in better control of MHCR kochia (87% to 100%) as compared to their individual applications (23% to 92%) across both sites except 2,4-D. These results suggest that pyridate can play a crucial role in various postemergence herbicide mixtures for effective control of MHCR kochia.

Outdoor studies were conducted to determine the extent of leafy spurge biomass reduction resulting from broadcast application of 2,4-D (2,244 g ae ha−1) with and without wiper-applied glyphosate. Glyphosate (575 g ae L−1) was applied at 0%, 33%, 50%, and 75% diluted concentrate with a wiper 24 h after 2,4-D was broadcast-applied. Injury estimates and shoot biomass did not differ between plants treated with 2,4-D only or when glyphosate was wiper-applied 21 d after treatment. Shoot regrowth biomass of plants treated with 2,4-D only was approximately 560% greater than nontreated plants 3 mo after treatment. Plants treated with wiper-applied glyphosate exhibited shoot regrowth biomass of less than 10% compared with nontreated plants 3 mo after treatment. Root biomass of plants treated with 2,4-D only (160% of nontreated plants) exhibited a similar pattern of shoot regrowth biomass. Root biomass of plants treated with wiper-applied glyphosate exhibited approximately 50% reductions compared with nontreated plants. All vegetative metrics were equally reduced with all tested concentrations of glyphosate; therefore, all labeled concentrations should be effective. The results of the experiment indicate that broadcast-applied 2,4-D is more effective at reducing leafy spurge biomass with the addition of wiper-applied glyphosate.

North Carolina growers have long struggled to control Italian ryegrass, and recent research has confirmed that some Italian ryegrass biotypes have become resistant to nicosulfuron, glyphosate, clethodim, and paraquat. Integrating alternative management strategies is crucial to effectively control such biotypes. The objectives of this study were to evaluate Italian ryegrass control with cover crops and fall-applied residual herbicides and investigate cover crop injury from residual herbicides. This study was conducted during the fall/winter of 2021–22 in Salisbury, NC, and fall/winter of 2021–22 and 2022–23 in Clayton, NC. The study was designed as a 3 × 5 split-plot in which the main plot consisted of three cover crop treatments (no-cover, cereal rye at 80 kg ha−1, and crimson clover at 18 kg ha−1), and the subplots consisted of five residual herbicide treatments (S-metolachlor, flumioxazin, metribuzin, pyroxasulfone, and nontreated). In the 2021–22 season at Clayton, metribuzin injured cereal rye and crimson clover 65% and 55%, respectively. However, metribuzin injured both cover crops ≤6% in 2022–23. Flumioxazin resulted in unacceptable crimson clover injury of 50% and 38% in 2021–22 and 2022–23 in Clayton and 40% in Salisbury, respectively. Without preemergence herbicides, cereal rye controlled Italian ryegrass by 85% and 61% at 24 wk after planting in 2021–22 and 2022–23 in Clayton and 82% in Salisbury, respectively. In 2021–22, Italian ryegrass seed production was lowest in cereal rye plots at both locations, except when it was treated with metribuzin. For example, in Salisbury, cereal rye plus metribuzin resulted in 39,324 seeds m–2, compared to ≤4,386 seeds m–2 from all other cereal rye treatments. In 2022–23, Italian ryegrass seed production in cereal rye was lower when either metribuzin or pyroxasulfone were used preemergence (2,670 and 1,299 seeds m–2, respectively) compared with cereal rye that did not receive an herbicide treatment (5,600 seeds m–2). cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.)

Waterhemp has become a serious management challenge for field crop growers in New York. Two putative glyphosate-resistant (GR) waterhemp populations (NY1 and NY2) were collected in 2023 from two soybean fields in Seneca County, NY. The objectives of this research were to 1) confirm and characterize the level of glyphosate resistance in waterhemp populations from New York relative to a known glyphosate-susceptible population from Nebraska (NE_SUS), and 2) evaluate the efficacy of various postemergence herbicides for GR waterhemp control. Based on the shoot dry weight reductions (GR50 values) in a dose-response study, the NY1 and NY2 populations exhibited 5.6- to 8.3-fold resistance to glyphosate compared with the NE_SUS population. In a separate study, postemergence herbicides such as dicamba, glufosinate, lactofen, and 2,4-D applied alone or in a mixture with glyphosate or glufosinate had provided 89% to 99% control and ≥97% shoot dry weight reduction of NY1 and NY2 populations 21 d after treatment. Greater than 98% control of the NE_SUS population was achieved with tested postemergence herbicides, except mesotrione (62% control). Furthermore, atrazine, chlorimuron + thifensulfuron, and mesotrione were the least effective in controlling NY1 and NY2 populations (42% to 59% control and 50% to 67% shoot dry weight reductions, respectively). These results confirm the first report of GR waterhemp in New York. Growers should adopt effective alternative postemergence herbicides tested in this study to manage GR waterhemp.

Increasing instances of herbicide-resistant annual bluegrass have limited turf managers’ options for chemical control. Endothall inhibits serine threonine protein phosphatase, a novel site of action for warm-season turf, and endothall use in hybrid bermudagrass is not extensively reported. Greenhouse studies were conducted to evaluate herbicide-resistant annual bluegrass response to endothall. Five herbicide-resistant annual bluegrass biotypes were treated with increasing endothall rates and compared to two susceptible populations. One glyphosate-resistant annual bluegrass biotype was 2.3- to 3.3-fold more resistant to endothall depending on trial and susceptible biotype, and all other biotypes were endothall susceptible. Four field studies were established from 2022 to 2023 to evaluate the influence of endothall rate and application timing on bermudagrass and manilagrass turf injury and annual bluegrass control. These studies were arranged as a 3 × 4 factorial with three levels of application timing (fully dormant, 50% green, and 100% green) and four levels of herbicide (endothall applied at 1.12, 1.68, and 2.24 kg ai ha−1 and trifloxysulfuron applied at 27.8 g ai ha−1). Maximum observed turf injury was dependent on endothall rate and timing and was commercially acceptable (<30%) at the low and middle rates when applied to 100% green bermudagrass and at all rates when applied to dormant turf. When applied to 50% green turf (mid-transition), endothall unacceptably injured warm-season turf regardless of application rate. Endothall controlled annual bluegrass more effectively when applied during mid-transition and 100% green turf than it did when applied during fully dormant turf. When applied at rates of 1.68 and 2.24 kg ai ha−1 during mid-transition or at 100% green turf, endothall controlled annual bluegrass 83% to 95%. Results from these studies indicate that endothall selectively controls herbicide-resistant annual bluegrass in warm-season turf but that selectivity and performance depend on application timing.

The windmill palm is a distinctive outdoor ornamental palm adapted to cooler climates. Weeds pose significant challenges in palm nurseries, particularly during seedling and establishment stages. This research was conducted in a nursery with 5,500 windmill palm seedlings, starting in April 2014, when the palm trees were 3 yr old. Experiments were terminated in October 2018 when weed control was no longer necessary due to the advanced growth of the palm trees. The objectives of this study were to determine the weed composition and diversity, elucidate the effects of mechanical weed management (MWM) on growth rate of palm, and develop a sustainable program to maximize palm tree growth through effective weed management and soil tillage. Few herbicides are registered for nursery use in Türkiye, thus weed control was performed mechanically using garden hoeing machines between rows and hand hoeing for intrarow strips. The most common and dense weeds were purple nutsedge, annual mercury, and common purslane in summer and autumn, and burning nettle in winter and spring. In 2014, weed densities were 100, 127, and 145 weeds m–2 for MWM, hand-weeding (HW), and nontreated (NT) plots, respectively. Transplanted palm seedlings required at least two, ideally three growing seasons of intensive weed control until the palm tree crowns block sunlight and suppress weed growth. The research indicated that palm trees in the MWM treatment had approximately 84 leaves and a height of 210 cm by October 2018, compared with 54 leaves and a height of 136 cm for HW, and 40 leaves and 100 cm height for NT. These results highlight the critical role of MWM in promoting optimal growth of Chinese windmill palms. Effective and sustainable weed management, combining MWM and HW, is essential for producing high-quality palm trees. The research provides valuable insights for nursery managers and contributes to best practices for cultivating windmill palm trees in similar climatic regions.

Glufosinate resistance was previously confirmed in three Palmer amaranth accessions from Arkansas (MSR1, MSR2, and CCR). Greenhouse screening results suggested the presence of multiple herbicide resistance. Therefore, this study aimed to determine the postemergence resistance profile of these three glufosinate-resistant Palmer amaranth accessions. Field experiments were also conducted to assess preemergence and postemergence herbicide options to control the accession with the highest glufosinate resistance level (MSR2). A dose-response assay with the three resistant accessions and two susceptible standards was conducted with the herbicides 2,4-D, atrazine, dicamba, diuron, fomesafen, glyphosate, imazethapyr, and mesotrione. The preemergence and postemergence field experiments with MSR2 evaluated 15 and 16 single active ingredients, respectively. The Palmer amaranth accessions that carried glufosinate resistance were also confirmed to be resistant to six other postemergence herbicides: 2,4-D, diuron, fomesafen, glyphosate, imazethapyr, and mesotrione. CCR is also resistant to dicamba. Therefore, accessions MSR1, MSR2, and CCR have evolved resistance to postemergence herbicides pertaining to seven sites of action. A shift toward increased tolerance to atrazine has also been observed among all resistant accessions. Overall, field preemergence treatments with atrazine, pyroxasulfone, or trifludimoxazin obtained the highest MSR2 control levels at all evaluation times and the lowest number of seedlings emerging at 3 and 6 wk after treatment. In the postemergence experiment, only paraquat obtained MSR2 control levels above 90% at all ratings. The lowest number of alive MSR2 plants was observed after postemergence treatments with paraquat or trifludimoxazin. Fields near where glufosinate resistance has been confirmed in Palmer amaranth will likely demand a more diverse and proactive management strategy that relies on combinations of chemical, cultural, and mechanical control tactics. Future efforts should focus on sequential applications and mixture, the elucidation of all resistance mechanisms in the evaluated accessions, and soil-applied dose-response.

Fluridone was registered for use in rice production in 2023, offering a new herbicide site of action for growers. However, little information is available on the degree of rice tolerance to this herbicide. Field experiments conducted in 2022 and replicated in 2023 near Colt, AR, evaluated the tolerance of 12 rice cultivars to fluridone, applied preemergence or at the 3-leaf growth stage, in separate experiments. Each experiment consisted of one cultivar. Fluridone rates included 0, 168 (1 × label rate), and 336 (2 × label rate) g ai ha−1 in all experiments. Visible injury varied between years in all experiments, likely due to different environmental conditions. In 2022, injury following preemergence applications of fluridone was below 25% across cultivars. In contrast, in 2023, injury ≥30% occurred to five cultivars, with a maximum of 58% observed for the cultivar ‘DG263L’. In both years, only three cultivars exhibited injury ≥20% following fluridone applications at the 3-leaf stage. Fluridone negatively affected shoot density, groundcover, chlorophyll content, and days to 50% heading in most cultivars when applied preemergence. When fluridone was applied to 3-leaf rice, at least one of the variables evaluated was negatively affected in two and nine cultivars in 2022 and 2023, respectively. Grain yield reductions of at least 18% were observed from eight cultivars in 2022, and a grain yield decrease from 9% to 49% from eight cultivars occurred in 2023 in the preemergence experiments. Fluridone applied to rice at the 3-leaf stage did not cause a yield penalty to any cultivar in 2022, whereas in 2023, a yield loss occurred from eight cultivars. Yield loss from the DG263L cultivar occurred at the 1 × rate in both experiments, indicating that this cultivar appears to be sensitive to fluridone, regardless of the application timing. Based on these findings, fluridone tolerance is cultivar-dependent. Furthermore, preemergence applications of fluridone to rice should be avoided.

Tetflupyrolimet is the first herbicide with a novel site of action (SOA) labeled PRE and early POST for use in agronomic crops to be labeled in the last three decades. Direct-seeded paddy rice field experiments were conducted near Stuttgart, AR, on a silt loam soil and near Keiser, AR, on a clay soil to evaluate tetflupyrolimet-containing herbicide programs in comparison to commercial standards in conventional, imidazolinone-resistant, and quizalofop-resistant rice systems. Additionally, a furrow-irrigated rice experiment was conducted near Colt, AR, and Keiser to ensure weed control with clomazone and tetflupyrolimet mixtures compared to commercial standards. Twelve commonly planted rice cultivars were also evaluated in response to a single PRE or POST (2- to 3-leaf rice) application of tetflupyrolimet at 200 or 400 g ai ha−1 in a paddy rice system near Colt. When averaged over soil texture and site-year, all herbicide programs provided ≥98% barnyardgrass control at 56 d after (DA) the last application. Visible rice injury varied for each rice system. Still, injury rarely differed among herbicide programs, except at a single evaluation timing in the conventional (7 DA, 3- to 4-leaf applications) and quizalofop-resistant (preflood) systems. All 12 rice cultivars displayed high tolerance to a single PRE or POST application of tetflupyrolimet at 200 or 400 g ai ha−1. No visible injury, stand loss, or negative impact on rice maturity or reduced grain yield was observed for any cultivar. Tetflupyrolimet will be an effective alternative SOA in a program approach for barnyardgrass while maintaining excellent rice crop safety.

As mid-southern U.S. rice producers continue to adopt furrow-irrigated rice production practices, supplementary management efforts will be vital in combating Palmer amaranth due to the extended germination period provided by the lack of a continual flood. Previous research has revealed the ability of cover crops to suppress Palmer amaranth emergence in corn, cotton, and soybean production systems; however, research on cover crop weed control efficacy in rice production is scarce. Therefore, trials were initiated in Arkansas in 2022 and 2023 to evaluate the effect of cover crops across five site-years on rice emergence, groundcover, grain yield, and total Palmer amaranth emergence. The cover crops evaluated were cereal rye, winter wheat, Austrian winterpea, and hairy vetch. Cover crop biomass accumulation varied by site-year, ranging from 430 to 3,440 kg ha−1, with cereal rye generally being the most consistent producer of high-quantity biomass across site-years. Rice growth and development were generally unaffected by cover crop establishment; however, all cover crops reduced rice emergence by up to 30% in one site-year. Rice groundcover was reduced by 13% from cereal rye in one site-year 2 wk before heading but cover crops did not affect rough rice grain yield in any of the site-years. Palmer amaranth emergence was reduced by 19% and 35% with cereal rye relative to the absence of a cover crop when rice was planted in April in Marianna, and May in Fayetteville, respectively. In most trials, Palmer amaranth emergence was not reduced by a cereal cover crop. In most instances, legume cover crops resulted in less Palmer amaranth emergence than without a cover crop. Based on these results, legume cover crops appear to provide some suppression of Palmer amaranth emergence in furrow-irrigated rice while having a minimal effect on rice establishment and yield.

Systematically monitoring the baseline sensitivity of troublesome weeds to herbicides is a crucial step in the early detection of their market lifespan. Florpyrauxifen-benzyl is one of the most important herbicides used in rice production throughout the world, and has been used for 5 yr in China. Barnyardgrass is one of the main targeted weed species of florpyrauxifen-benzyl. In total, 114 barnyardgrass populations were collected from rice fields in Jiangsu Province, China, and using whole-plant bioassays they were screened for susceptibility to florpyrauxifen-benzyl. The GR50 values (representing the dose that causes a 50% reduction in fresh weight of aboveground parts) of florpyrauxifen-benzyl for all populations ranged from 1.0 to 34.5 g ai ha−1, with an average of 6.8 g ai ha−1, a baseline sensitivity dose of 3.3 g ai ha−1, and a baseline sensitivity index of 34.5. Twenty-one days after treatment with florpyrauxifen-benzyl at the labeled dose (36 g ai ha−1), 90% of the barnyardgrass populations exhibited >95% reductions in fresh weight of aboveground parts. Compared with the baseline sensitivity dose, 63, 44, and 7 populations had, respectively, no resistance (55%), low resistance (39%), and moderate resistance (6%) to florpyrauxifen-benzyl. Furthermore, the GR50 distribution of barnyardgrass populations did not show a significant correlation with collection location, planting method (direct-seeding or transplanting), or rice species (Oryza sativa L. ssp. indica or ssp. japonica) at any of rice fields where seeds had been collected (P > 0.05). In conclusion, florpyrauxifen-benzyl remains effective for barnyardgrass control in rice fields despite serious resistance challenges.

Weeds belonging to the Amaranthus family are most problematic for soybean producers. With Palmer amaranth evolving resistance to multiple herbicides labeled for use in soybean, producers seek new sites of action to integrate into season-long herbicide programs. Bayer CropScience plans to launch a Convintro™ brand of herbicides, one being a premixture that will include diflufenican (categorized as a Group 12 herbicide by the Weed Science Society of America [WSSA]), metribuzin (WSSA Group 5), and flufenacet (WSSA Group 15), for use preemergence in soybean. Research trials were conducted in Fayetteville and Keiser, AR, and Holt, MI, in 2022 and 2023, to evaluate the premixture in a season-long program in a dicamba-resistant soybean system. A 0.17:0.35:0.48 ratio of a premixture of diflufenican:metribuzin:flufenacet (DFF-containing premixture) was applied preemergence with different combinations of glyphosate, glufosinate, dicamba, and acetochlor at 28 (early postemergence) and 42 (late postermergence) days after planting (DAP). At the early postemergence timing, the DFF-containing premixture provided >90% control of Palmer amaranth and prickly sida. However, common ragweed, common lambsquarters, morningglory ssp., and annual grass control was ≤80% at this timing. When the late postemergence applications occurred, treatments that had already received an early postemergence application controlled prickly sida, morningglory ssp., Palmer amaranth, and annual grasses to a greater extent than those that had not, indicating the preemergence application of the DFF-containing premixture was not sufficient to provide control of the weed spectrum through 42 DAP. By 70 DAP, all programs provided ≥93% control of all weeds evaluated. Herbicide programs that included the DFF-containing premixture preemergence followed by (fb) EPOST fb LPOST common ragweed, common lambsquarters, morningglory ssp., and annual grasses to a greater than the one-pass postemergence systems. In addition, all herbicide programs evaluated in this study reduced Palmer amaranth seed production by >99%. However, producers who plan to use the DFF-containing premixture may need two postemergence herbicide applications to obtain high levels of weed control throughout the growing season.

Trifludimoxazin is a new herbicide that inhibits protoporphyrinogen oxidase and is being evaluated for the control of small-seeded annual broadleaf weeds and grasses in several crops. Currently, no information is available regarding peanut cultivar response to trifludimoxazin and its utility in peanut weed control systems. Three unique field experiments were conducted and replicated in time from 2019 through 2022 to determine the response of seven peanut cultivars (‘AU-NPL 17’, ‘FloRun 331’, ‘GA-06G’, ‘GA-16HO’, ‘GA-18RU’, ‘GA-20VHO’, and ‘TifNV High O/L’) to preemergence applications of trifludimoxazin and to determine the efficacy of trifludimoxazin at multiple rates and tank-mixtures with acetochlor, diclosulam, dimethenamid-P, pendimethalin, and S-metolachlor for weed management. Cultivar sensitivities to trifludimoxazin were not observed. Peanut density was not reduced by any trifludimoxazin rate. Compared with nontreated controls, in 2019 when trifludimoxazin was applied at 75 g ai ha−1, leaf necrosis increased by 18% and peanut stunting increased by 10%, and yield was reduced by 6%. However, this rate increased leaf necrosis by only 4%, stunting by 3% to 5%, and it had no negative effect on yield in 2020–2021. Generally, peanut injury from preemergence-applied trifludimoxazin was similar to or less than that observed from flumioxazin at 2 wk after application (WAA). Peanut yield in the weed control study was reduced by 11% to 12% when treated with trifludimoxazin at 150 g ha−1 (4× the standard rate) when compared to the 75 g ha−1 rate. However, yield was not different from the flumioxazin treatment. Palmer amaranth control with trifludimoxazin combinations was ≥91% at 13 WAA, wild radish control was ≥96% at 5 WAA, and annual grass control was ≥97% at 13 WAA. Peanut is sufficiently tolerant of 38 g ha−1 of trifludimoxazin, and when tank-mixed with other residual herbicides provides weed control similar to flumioxazin-based systems.

Bermudagrass is the most troublesome and difficult-to-control perennial grass weed in Florida sugarcane. Once established, it may be effectively controlled only during the sugarcane fallow period using a combination of nonselective herbicides and tillage. Options for selective management of bermudagrass that escape sugarcane fallow period management programs must be evaluated to mitigate its progressive increase as the crop cycle increases from plant cane to ratoon crops. Greenhouse and field studies were conducted in Belle Glade, Florida, from 2017 to 2018, to determine the response of newly established bermudagrass from sprigs with stolons to two or three sequential applications of topramezone (25 and 50 g ha−1) every 14 d, and combinations of topramezone (25 and 50 g ha−1) with herbicides that inhibit photosystem II (PS II) such as atrazine (2,240 g ha−1), ametryn (440 g ha−1), and metribuzin (2,240 g ha−1). Two or three sequential applications of topramezone with a cumulative total of 75 to 100 g ha−1 provided >93% bermudagrass control 42 d after the first sequential application under greenhouse and field conditions. These treatments exhibited 12% chance of survival 70 d after the first sequential application. There was an additive effect of PS II-inhibitor herbicides on bermudagrass control in mixtures with topramezone. The mixture of topramezone (50 g ha−1) with metribuzin and atrazine provided more than 87% and 92% bermudagrass control under greenhouse and field conditions, respectively, 42 d after treatment. Bermudagrass treated with topramezone (50 g ha−1) in a mixture with metribuzin exhibited 23% chance of survival 70 d after treatment. The results show good efficacy of sequential topramezone applications every 14 d or in a mixture with the PS II-inhibitor herbicides atrazine and metribuzin for control of newly established bermudagrass that typically escape control measures during the sugarcane fallow management period.