Weed competition and rising herbicide costs, especially for managing resistant populations, pose major challenges to peanut production in the southeastern United States. These concerns have increased interest in cover crops as a component of integrated weed management strategies to reduce herbicide reliance and enhance sustainability. Field experiments were conducted in Florida during the 2022-2023 and 2023-2024 seasons to evaluate the effects of cereal rye residue management and herbicide programs on weed suppression and peanut yield. Treatments included three residue management strategies: rolled rye, standing rye, and winter fallow, and four herbicide programs: PRE (flumioxazin), POST (imazapic + dimethenamid-P+ 2,4-DB), PRE + POST (fluridone followed by paraquat + bentazon +S-metolachlor), and a nontreated control. In the absence of PRE herbicides, cereal rye residue reduced weed density and biomass by up to 45% and 57%, respectively, compared to winter fallow. Weed density and biomass with rolled or standing rye combined with POST herbicide was comparable to the full PRE + POST herbicide program in fallow plots. While weed suppression was similar between rolled and standing rye, standing rye increased peanut canopy height and reduced peanut yield by up to 21%, likely due to shading. Rolled rye increased yield by 26% and 10% compared to standing rye and winter fallow, respectively. POST and PRE plus POST herbicide programs provided higher levels of weed control and yield than PRE herbicide program alone. The results indicate that integrating high-residue cereal rye with effective POST herbicide programs can reduce dependence on PRE herbicides without compromising weed control or peanut productivity.

This publication is a tool to aid turfgrass professionals, Extension specialists, and clientele in the identification and management of goosegrass in Florida turfgrasses. Written by Pawel Petelewicz and Gregory E. MacDonald, and published by the UF/IFAS Department of Agronomy, February 2025.

Recognition ® is a new trifloxysulfuron‐sodium formulation containing metcamifen safener (i.e., trifloxysulfuron‐sodium & metcamifen; TSM) enabling tank‐mixing with fluazifop‐P‐butyl (FPB) for selective bermudagrass ( Cynodon spp.) control in St. Augustinegrass [ Stenotaphrum secundatum (Walter) Kuntze], the predominant lawn species in Florida. Three studies were conducted from August to November of 2022 and May to October of 2023 in north‐central Florida to ensure the safety of TSM ± FPB to CitraBlue, Classic, Floratam, Palmetto, and Seville St. Augustinegrass maintained as a home lawn. Herbicides (TSM at 18 or 28 g ai ha −1 and FPB at 210, 315, or 420 g ai ha −1 alone or combined) were applied two or three times every 4 weeks from August 12, 2022 (Study 1), twice every 6 weeks from June 7, 2023 (Study 2), and once or twice every 6 weeks beginning in the spring (from May 5) or in the summer (from July 11) of 2023 (Study 3). All treatments in Study 1 provided excellent bermudagrass control but caused severe injury to Seville St. Augustinegrass. In Study 2, only FPB alone led to unacceptable damage, with no differences in herbicide tolerance among CitraBlue, Floratam, and Palmetto cultivars. Study 3 confirmed CitraBlue safety to TSM‐based treatments and a higher risk of injury in Seville. Overall, greater phytotoxicity was observed with later‐season applications (summer in Study 3 and late summer in Study 1), suggesting increased sensitivity in more susceptible St. Augustinegrass cultivars as the season progresses. While the exact reasons for this require further investigation, our results suggest that metcamifen may not provide effective safening in certain sensitive cultivars, particularly with late‐season applications. Therefore, practitioners should exercise caution when using TSM, ideally conduct small‐scale tests before broadcasting, and avoid applications in late summer or fall.

Water hyacinth is a highly invasive aquatic species in the southern United States that requires intensive management through frequent herbicide applications. Quantifying management success in large-scale operations is challenging with traditional survey methods that rely on boat-based teams and can be time-consuming and labor-intensive. In contrast, an unmanned aerial system (UAS) allows 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 UAS-based red-green-blue imagery. Penoxsulam, carfentrazone, diquat, 2,4-D, florpyrauxifen-benzyl, and glyphosate were applied at two rates, and experimental units were evaluated for 6 wk. 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 with carfentrazone and penoxsulam treatments (> −0.70), and the 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 VIs were satisfactory predictors of mid-range visually evaluated herbicide efficacy values but were poorly correlated with extremely low and high values, corresponding to nontreated and necrotic plants. Future research should focus on applying findings to real-world (nonexperimental) field conditions and testing imagery with spectral bands beyond the visible range.

Goosegrass [ Eleusine indica (L.) Gaertn.] is one of the most troublesome warm-season grassy weeds in subtropical climates of the southern United States. Currently, postemergence options are highly limited, and goosegrass control (GC) becomes more difficult as plants mature. Among current options, topramezone can control mature goosegrass. Research conducted in Florida suggests that despite seemingly effective control, recovery may be occurring from surviving roots. Therefore, this study assessed strategies aimed to ensure the persistent removal of mature goosegrass populations of Florida ecotypes. Two greenhouse studies were conducted to evaluate the response of goosegrass at one to three tillers and 4–10 tillers to topramezone applied once at rates from 0.8 to 12.2 g a.i. ha −1 (study 1) and at total rate reduced to 6.1 g a.i. ha −1 applied once or equally divided into two, four, or eight biweekly applications (study 2). Single topramezone applications at 6.1 g a.i. ha −1 provided comparable GC and biomass reduction to single applications at 12.2 g a.i. ha −1 . Reduced rate-based split-programs of two and four biweekly applications improved GC and its persistence over a single application as evidenced by a >250 increase in GC area under the progress curve and a >20 days increase in days over 80% GC. Among the proposed extended application programs based on the reduced effective rate of topramezone, the most promising consists of four biweekly applications at a 0.125× rate, equivalent to 1.53 g a.i. ha −1 .

Goosegrass [Eleusine indica (L.) Gaertn.] is a difficult-to-control grassy weed occurring in compacted soils or heavy-traffic areas including golf greens. In Florida, goosegrass survives as a short-lived perennial, and eradication becomes more challenging as the plant matures. Currently, only foramsulfuron (FOR) is registered for postemergence goosegrass control in hybrid bermudagrass [Cynodon dactylon (L.) Pers. x Cynodon transvaalensis Burtt-Davy] putting surfaces. A 2-year study evaluated the impact of three aerification treatments (none vs. once year-1 or twice year-1) followed by herbicide applications (FOR at 0.029 kg ha-1, simazine at 0.525 kg ha-1, metribuzin at 0.210 kg ha-1, topramezone [TOP] at 0.006 kg ha-1, and mesotrione [MES] at 0.175 kg ha-1) to control mature goosegrass in a TifEagle hybrid bermudagrass putting green in Davie, FL. The impact of immediate post-herbicide irrigation on turf safety was also investigated. Aerification treatments were initiated in June, and herbicides were applied approximately 1 week after each aerification event. FOR did not effectively control goosegrass, while tank-mixes of mesotrione + topramezone tank-mix and simazine + mesotrione tank-mix provided effective control but produced unacceptable phytotoxicity. Post application irrigation reduced turf injury with TOP and MES alone in 2021, and weed control in both years. Aerification did not influence goosegrass control or turf safety.

Diverse datasets are crucial for training machine learning-based weed recognition models. However, annotating (i.e., labeling) images can be laborious and time-consuming. Choice of annotation method and training approach not only affects the overall model effectiveness but also its minimum training data requirements and development pace. Segmentation and semi-supervised learning (SSL) may offer performance or training enhancements. This study evaluated (1) segmentation against object detection in spotted spurge [ Chamaesyce maculata (L.) Small] recognition in Latitude 36 hybrid bermudagrass [ Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] maintained as a golf course fairway and (2) the potential of two-step SSL-based training procedure using data labeled both manually and automatically with a pre-trained model to expedite the model development. The architecture used across this research was You Only Look Once version 8 (YOLOv8) employing nano, small, and medium variants. All models were trained with a dataset restricted to 1200 training and 300 validation images. Both annotation methods resulted in adequate spotted spurge identification, as evidenced with >0.60 (>0.50 acceptability threshold) medium average precision at intersection over union threshold of 0.50 (mAP@50). Although the difference was minimal, object detection performed superior to segmentation. The two-step training effectively accelerated image annotation while preserving or improving (with 8:4 and 6:6 splits between manually and auto-labeled data) object detection performance. Segmentation tolerated only 10:2 split and exhibited increased sensitivity to declining dataset quality proportionally to the increase in auto-labeled images in the final training dataset. Findings show a two-step SSL-based training procedure expedites annotation, enhancing model development efficiency.

Weed management in peanut primarily relies on intensive herbicide programs. Integrating cereal rye as a cover crop may reduce herbicide input without compromising weed control. Field experiments were conducted to evaluate cereal rye termination management and herbicide programs in peanut. Main plot treatments included a winter fallow control and four cereal rye termination scenarios: 1) early termination 28 d before peanut planting (DBP) with residue rolled flat; 2) early termination 28 DBP with residue left standing; 3) late termination 14 DBP with residue rolled flat; or 4) late termination 14 DBP with residue left standing. Subplot treatments consisted of four herbicide programs: 1) preemergence + early postemergence + mid-postemergence herbicides; 2) preemergence + mid-postemergence herbicides; 3) early postemergence + mid-postemergence herbicides; and 4) a nontreated control. Early cereal rye termination (28 DBP), whether rolled or standing, reduced Palmer amaranth density by 36% to 48% without preemergence herbicides and by 36% to 50% when preemergence herbicides (fluridone or flumioxazin) were applied. Sicklepod density was unaffected by early termination. In contrast, late termination reduced sicklepod density by 47% to 50% and Palmer amaranth density by 64% to 86% relative to the winter fallow control at 28 d after preemergence application. Across all treatments, cereal rye reduced Palmer amaranth and sicklepod biomass by 63% to 67% and 63% to 65%, respectively, 28 d after mid-postemergence herbicides were applied. However, standing cereal rye residue reduced peanut yield compared to rolled residue and the winter fallow. Late-terminated, rolled cereal rye residue combined with reduced herbicide programs (preemergence + mid-postemergence or early postemergence + mid-postemergence) provided weed control and yield comparable to the intensive herbicide program (preemergence + early postemergence + mid-postemergence) in winter fallow control. Based on these findings, late-terminated, rolled cereal rye has the potential to reduce herbicide input while maintaining peanut yield and effective weed suppression.

Tropical signalgrass (TSG [ Urochloa distachya (L.) T.Q. Nguyen]) is difficult to control in Florida turfgrass due to limited herbicide options, perennial life cycle, aggressive growth, and ability to reestablish from stolons and seeds. Field studies in central Florida were conducted in 2022 and 2023–2024 to identify effective herbicide combinations for controlling severe (i.e., ≥50% cover) TSG infestations in a hybrid bermudagrass [BGR Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] athletic field. Application timing (spring/summer [S/S Seq.] vs. fall/winter [F/W Seq.]) and turfgrass recovery were also assessed. Herbicide treatments (topramezone [TPZ; 12 or 18 g ha −1 ], quinclorac [QNC; 841 g ha −1 ], amicarbazone [AMC; 175 or 254 g ha −1 ], imazapic [IMC; 70 g ha −1 ], glyphosate [GLY; 140 or 280 g ha −1 ], glufosinate [GLU; 553 or 840 g ha −1 ], pinoxaden [PNX; 154 g ha −1 ], thiencarbazone + foramsulfuron + halosulfuron [TFH; 355 + 710 + 1105 g ha −1 ]) were applied alone or combined every 2 weeks for a total of two applications, starting from August 3, 2022 (Study 1) and May 18, 2023, or October 11, 2023 (Study 2; PNX, IMC, and GLU only). In Study 1, only PNX and GLU-based treatments effectively controlled TSG. Study 2 showed similar results, with IMC plus a low rate of GLU providing similar control to the higher rate of GLU alone. TSG removal was faster in the S/S Seq., but only the F/W Seq. consistently prevented reestablishment. GLU-based treatments caused rapid, severe BGR injury, though complete regeneration followed within 6–8 weeks after initial treatment (WAIT). Recovery was slower with F/W Seq. in Study 2 compared to Study 1.

Esta publicación es una herramienta destinada a asistir a profesionales del césped, especialistas en Extensión y clientes, en la identificación y el manejo de la maleza conocida como “pata de gallina” o “goosegrass” (en inglés) en los céspedes de Florida. Este documento es SS-AGR-488-Span, una publicación del Department of Agronomy, UF/IFAS Extension. Fecha original de publicación: abril 2025.

Benghal dayflower and sicklepod are weeds of economic importance in peanut in the southeastern United States due to their extended emergence pattern and limited effective herbicides for control. Field studies were conducted near Jay, Florida, in 2022 and 2023, to evaluate the effect of planting date and herbicide combinations on Benghal dayflower and sicklepod control in peanut crops. Peanut planted in June was exposed to a higher Benghal dayflower density than peanut planted in May. Sicklepod density was similar between May and June planting dates at 28 d after preemergence and early postemergence herbicide applications, but density was greater in peanut that was planted in June, 28 d after the mid-postemergence application. A preemeergence herbicide application followed by (fb) an early postemergence application of S-metolachlor or diclosulam + S-metolachlor controlled Benghal dayflower 84% to 93% 28 d after early postemergence in peanut that was planted in May, but control was reduced to 58% to 78% in the crop that had been planted in June. Regardless of planting date, a preemeergence application fb S-metolachlor or diclosulam + S-metolachlor applied early postemergence provided < 80% sicklepod control 28 d after early postemergence. Imazapic + dimethenamid-P + 2,4-DB applied postemergence improved Benghal dayflower control to at least 94% 28 d after mid-postemergence, but sicklepod control was not > 85%. Regardless of the planting date, paraquat + bentazon + S-metolachlor applied early postemergence was required to achieve >= 95% sicklepod control. However, herbicide combinations that included paraquat + bentazon + S-metolachlor reduced peanut yield when planting was delayed to June. In fields that are infested with Benghal dayflower and sicklepod, it is recommended that peanut be planted in early May to minimize the potential impact of these weeds and to increase peanut yield. Late-planted peanut required more intensive herbicide applications to obtain the same peanut yield as the May-planted peanut.

Sicklepod is one of the most difficult to control weeds in peanut production in the southeastern United States due to its extended emergence pattern and limited effective herbicides for control. Growers rely on preemergence herbicides as the foundation of their weed control programs; however, postemergence herbicides are often needed for season-long weed control. The objectives of this study were to evaluate the effect of planting pattern and herbicide combinations for sicklepod control in peanut crops. Due to rapid canopy closure, twin-row planting improved late-season sicklepod control by 13% and peanut yield by 5% compared with a single-row pattern. A preemergence application of fluridone, flumioxazin, or fluridone + flumioxazin provided 76% to 89% control of sicklepod 28 d after preemergence. Regardless of the herbicide applied preemergence, paraquat + bentazon + S-metolachlor applied early postemergence was required to achieve >= 90% sicklepod control 28 d after early postemergence. All preemergence herbicide treatments followed by (fb) S-metolachlor or diclosulam + S-metolachlor applied early postemergence provided <90% control 28 d after early postemergence. A mid-postemergence application of imazapic + dimethenamid-P + 2,4-DB controlled sicklepod by 67% to 79% prior to peanut harvest, and biomass reduction was unacceptable (<80%), resulting in difficulty in peanut digging. The highest peanut yield was observed when paraquat + bentazon + S-metolachlor was applied early postemergence fb imazapic + dimethenamid-P + 2,4-DB applied mid-postemergence. Based on the results of this study, a herbicide combination of paraquat + bentazon + S-metolachlor is an important early-season tool for controlling sicklepod in peanut crops. The results also showed that a twin-row planting pattern improved late-season sicklepod control but did not reduce herbicide input to protect peanut yield.

Carrier water quality is an important consideration for herbicide efficacy. Field and greenhouse studies were conducted from 2021 to 2023 to evaluate the effect of carrier water pH and hardness on imazapic efficacy for sicklepod control in peanut crops. In separate field experiments imazapic was applied postemergence at 0.071 kg ai ha(-1) with carrier water pH levels of 5, 6, 7, 8, or 9; and hardness levels of 0 (deionized water), 100, 200, 400, or 500 mg L-1 of CaCO3 equivalent. In greenhouse experiments, imazapic was applied to sicklepod that was either 10 cm, 15 cm, or 20 cm tall at similar carrier water pH levels and hardness levels of 0, 100, 200, 400, or 800 mg L-1 of CaCO3. In the field study, sicklepod control, density, and biomass reductions were lower with carrier water pH 5 or 9 compared with pH 7. In the greenhouse study, control was not different among carrier water pH levels when imazapic was applied to 10-cm-tall sicklepod; however, when applied to 15- or 20-cm-tall sicklepod, control was at least 25% greater with acidic (pH 5) compared to alkaline (pH 9) carrier water. Results from the field study showed that carrier water hardness <= 500 ppm did not reduce the efficacy of imazapic to control sicklepod. In the greenhouse study, regardless of sicklepod height, carrier water hardness of 800 mg L-1 reduced sicklepod control by 15% and biomass reduction by 17% compared with deionized water (pH 7). The effects of carrier water pH and hardness on imazapic efficacy did not compromise peanut yield in the field study. However, this study indicates that both acidic and alkaline carrier water pH and hardness (800 mg L-1 CaCO3 L-1) have the potential to reduce imazapic efficacy on sicklepod, and appropriate spray solution amendments maybe be needed to maintain optimum efficacy.

Targeted spraying application technologies have the capacity to drastically reduce herbicide inputs, but to be successful, the performance of both machine vision-based weed detection and actuator efficiency needs to be optimized. This study assessed (1) the performance of spotted spurge recognition in 'Latitude 36' bermudagrass turf canopy using the You Only Look Once (YOLOv3) real-time multiobject detection algorithm and (2) the impact of various nozzle densities on model efficiency and projected herbicide reduction under simulated conditions. The YOLOv3 model was trained and validated with a data set of 1,191 images. The simulation design consisted of four grid matrix regimes (3 x 3, 6 x 6, 12 x 12, and 24 x 24), which would then correspond to 3, 6, 12, and 24 nonoverlapping nozzles, respectively, covering a 50-cm-wide band. Simulated efficiency testing was conducted using 50 images containing predictions (labels) generated with the trained YOLO model and by applying each of the grid matrixes to individual images. The model resulted in prediction accuracy of an F1 score of 0.62, precision of 0.65, and a recall value of 0.60. Increased nozzle density (from 3 to 12) improved actuator precision and predicted herbicide-use efficiency with a reduction in the false hits ratio from similar to 30% to 5%. The area required to ensure herbicide deposition to all spotted spurge detected within images was reduced to 18%, resulting in similar to 80% herbicide savings compared to broadcast application. Slightly greater precision was predicted with 24 nozzles but was not statistically different from the 12-nozzle scenario. Using this turf/weed model as a basis, optimal actuator efficacy and herbicide savings would occur by increasing nozzle density from 1 to 12 nozzles within the context of a single band.

Herbicides are the primary tool for controlling weeds in peanut ( Arachis hypogaea L.) and are crucial to sustainable peanut production in the United States. The literature on chemical weed management in peanut in the past 53 yr (1970 to 2022) in the United States was systematically reviewed to highlight the strengths and weaknesses of different herbicides and identify current research gaps in chemical weed management. Residual weed control in peanut is achieved mainly with dimethenamid- P , ethalfluralin, pendimethalin, and S -metolachlor. More recently, the use of the protoporphyrinogen oxidase inhibitor flumioxazin and acetolactate synthase inhibitors, such as diclosulam, for residual weed control in peanut has increased considerably. Postemergence broadleaf weed control in peanut is achieved mainly with acifluorfen, bentazon, diclosulam, imazapic, lactofen, paraquat, and 2,4-DB, while the graminicides clethodim and sethoxydim are the major postemergence grass weed control herbicides in peanut. Although several herbicides are available for weed control in peanut, no single herbicide can provide season-long weed control due to limited application timing, lack of extended residual activity, variability in weed control spectrum, and rotational restrictions. Therefore, effective weed management in peanut often requires herbicide mixtures and/or sequential application of preplant-incorporated, preemergence, and/or postemergence herbicides. However, the available literature showed a substantive range in herbicide efficacy due to variations in environmental conditions and flushes of weed germination across years and locations. Despite the relatively high efficacy of herbicides, the selection of herbicide-resistant weeds is another area of increasing concern. Future research should focus on developing new strategies for preventing or delaying the development of resistance and improving herbicide efficacy within the context of climate change and emerging constraints such as water shortages, rising temperatures, and increasing CO 2 concentration.

Cuban bulrush (Oxycaryum cubense) (Poepp. & Kunth) Lye is an epiphytic perennial sedge that invades aquatic habitats in the southeastern United States. Its emergent and floating growth habit allows it to form tussocks that restrict waterway access for navigation and outcompete native plant species. It is primarily managed using herbicides, and there is a need to evaluate more active ingredients for Cuban bulrush control. Three groups of single or tank mix herbicide applications were evaluated for control of Cuban bulrush in a greenhouse setting Florida. In trial 1, we evaluated operational treatments currently used by state agencies in Florida (diquat, glyphosate, 2,4-D, glyphosate þ flumioxazin, 2,4-D þ diquat, and 2,4-D þ glyphosate). In trial 2, we evaluated a recently registered synthetic auxin herbicide (florpyrauxifen-benzyl) alone or in combination with 2,4-D, imazamox, or flumioxazin. In trial 3, we evaluated several acetolactate synthase (ALS)-inhibitor herbicides (halosulfuron, imazapic, imazethapyr, bispyri-bac-sodium, imazapyr, and imazamox). Operational treat-ments and florpyrauxifen-benzyl combinations resulted in . 70% visual control 30 days after treatment (DAT) and . 90% biomass reduction of aboveground tissue 60 DAT. ALS-inhibiting herbicides resulted in slower symptom development, although there was limited regrowth (. 90% biomass reduction) 60 DAT for plants treated with imazapic, imazethapyr, imazamox, and imazapyr. Halosulfuron and bispyribac-sodium resulted in inconsis-tent levels of control between experimental runs. These small-scale results suggest that the current operational treatments as well as florpyrauxifen-benzyl combinations provide both fast and effective control of Cuban bulrush. Future work will focus on verifying these findings under operational field conditions.

Weed interference is a major factor that reduces peanut (Arachis hypogaea L.) yield in the United States. Peanut growers rely heavily on herbicides for weed control. Although effective, herbicides are not a complete solution to the complex challenge that weeds present. Therefore, the use of nonchemical weed management options is essential. The literature on weed research in peanut in the past 53 yr in the United States was reviewed to assess the achievements and identify current research gaps and prospects for nonchemical weed management for future research. More than half (79%) of the published studies were from the southeastern United States. Most studies (88%) focused on weed management, while fewer studies (12%) addressed weed distribution, ecology, and competitive mechanisms. Broadleaf weeds were the most frequently studied weed species (60%), whereas only 23% and 19% of the published studies were relevant to grasses and Cyperus spp., respectively. Seventy-two percent of the published studies focused on curative measures using herbicides. Nonchemical methods using mechanical (5%) and preventive (13%) measures that influence crop competition and reduce the buildup of the weed seedbank, seedling recruitment, and weed seed production have received less attention. In most studies, the preventive weed management measures provided weed suppression and reduced weed competition but were not effective enough to reduce the need for herbicides to protect peanut yield. Therefore, future research should focus on developing integrated weed management strategies based on multiple preventive measures rather than one preventive measure combined with one or more curative measures. We recommend that research on mechanical weed management should focus on the role of cultivation when integrated with currently available herbicides. For successful weed management with lasting outcomes, the dominant weed communities of specific target locations should be addressed within the context of climate change and emerging constraints rather than focusing on single problematic species.

Co-application of herbicides with other agrochemicals such as foliar fertilizers, fungicides, and insecticides is a common practice in crop production. This practice is widely adopted by growers because it saves time and re-duces labor costs associated with the sequential application of agrochemicals. In spite of these benefits, in-compatibility can be associated with these mixtures, which can reduce weed control and increase phytotoxicity to crops. The interaction of herbicides with co-applied agrochemicals can result in synergistic, antagonistic, or additive effects depending on the chemistry of the products, application variables, and environmental conditions. Foliar fertilizers co-applied with weak-acid herbicides show antagonistic effects occurring mostly with zinc and manganese and additive or synergistic effects occurring mostly with boron. Co-application of herbicides and insecticides belonging to organophosphate and carbamate groups generally results in antagonistic effects, reducing weed control efficiency, while co-applied pyrethroid insecticides seldom affect herbicide performance. Graminicides and weak-acid herbicides such as glyphosate and 2,4-D are the most susceptible to the antagonistic effect of co-applied fungicides. Although some combinations including strobilurin fungicides and organophos-phate and carbamate insecticides with herbicides inhibiting acetolactate synthase, some of photosystem II, and acetyl CoA carboxylase increased herbicides phytotoxicity to crops, yield is often not compromised. Adjuvants are recommended to mitigate the negative effects of co-applied agrochemicals on herbicide performance, but response varies with herbicides and weed species. More research is needed to determine the effect of co-applied agrochemicals on different herbicide chemistries across diverse weed categories to develop accurate recom-mendations for effective weed management in the future.

The fatty acid composition of seed oil is a major determinant of the flavor, shelf-life, and nutritional quality of peanuts. Major QTLs controlling high oil content, high oleic content, and low linoleic content have been characterized in several seed oil crop species. Here we employ genome-wide association approaches on a recently genotyped collection of 787 plant introduction accessions in the USDA peanut core collection, plus selected improved cultivars, to discover markers associated with the natural variation in fatty acid composition, and to explain the genetic control of fatty acid composition in seed oils. Overall, 251 single nucleotide polymorphisms (SNPs) had significant trait associations with the measured fatty acid components. Twelve SNPs were associated with two or three different traits. Of these loci with apparent pleiotropic effects, 10 were associated with both oleic (C18:1) and linoleic acid (C18:2) content at different positions in the genome. In all 10 cases, the favorable allele had an opposite effect - increasing and lowering the concentration, respectively, of oleic and linoleic acid. The other traits with pleiotropic variant control were palmitic (C16:0), behenic (C22:0), lignoceric (C24:0), gadoleic (C20:1), total saturated, and total unsaturated fatty acid content. One hundred (100) of the significantly associated SNPs were located within 1000 kbp of 55 genes with fatty acid biosynthesis functional annotations. These genes encoded, among others: ACCase carboxyl transferase subunits, and several fatty acid synthase II enzymes. With the exception of gadoleic (C20:1) and lignoceric (C24:0) acid content, which occur at relatively low abundance in cultivated peanut, all traits had significant SNP interactions exceeding a stringent Bonferroni threshold (α = 1%). We detected 7,682 pairwise SNP interactions affecting the relative abundance of fatty acid components in the seed oil. Of these, 627 SNP pairs had at least one SNP within 1000 kbp of a gene with fatty acid biosynthesis functional annotation. We evaluated 168 candidate genes underlying these SNP interactions. Functional enrichment and protein-to-protein interactions supported significant interactions (p- value < 1.0E-16) among the genes evaluated. These results show the complex nature of the biology and genes underlying the variation in seed oil fatty acid composition and contribute to an improved genotype-to-phenotype map for fatty acid variation in peanut seed oil. Key phrases SNP Genotyping, Genome-wide Association Study (GWAS), GWAS of interacting SNPs (GWASi), Pleiotropy, Seed fatty acid composition, Oleic-Linoleic acid ratio.

Field research evaluated peanut (Arachis hypogaea L.) tolerance and weed control with preemergence (PRE) followed by early postemergence (EPOST) herbicide programs: PRE pyroxasulfone, S-metolachlor, flumioxazin, pendimethalin, ethalfluralin, diclosulam, or dimethenamid-P, followed by EPOST application of paraquat + acetochlor + bentazon at 4 wk after PRE (WA-PRE). The herbicides resulted in no differences in peanut injury at 2 WA-PRE in 2019 but flumioxazin resulted in approximately two-fold greater injury (>22%) than other treatments in 2020 because of heavy rainfall at peanut cracking. Palmer amaranth (Amaranthus palmeri S.Watson) control with diclosulam was lower than with other herbicides. Carpetweed (Mollugo verticillata L.) control with S-metolachlor and dimethenamid-P was at least 10% lower than with pendimethalin, flumioxazin, or pyroxasulfone at 4 WA-PRE. Palmer amaranth control 2 wk after the EPOST (WA-EPOST) application was >94% for all treatments except diclosulam. Peanut injury at 2 WA-EPOST was <= 28% but was minimal by 8 WA-EPOST. Overall, yield with herbicide treatments was similar to the weedfree control. A greenhouse experiment evaluated postemergence herbicide combinations for Palmer amaranth control, including 2,4-DB, acifluorfen, imazapic, bentazon + acifluorfen, pyroxasulfone + carfentrazone, and various combinations of each. Palmer amaranth control (>= 99%) was greater and biomass (<= 0.3 g plant(-1)) was lower with acifluorfen treatments than with other treatments. The 2,4-DB + pyroxasulfone + carfentrazone treatment provided similar control to acifluorfen treatments. The EPOST paraquat + acetochlor + bentazon combinations following an effective PRE program will effectively control Palmer amaranth in peanut. Additionally, greenhouse experiments supported the use of acifluorfen for postemergence Palmer amaranth control.