Annual bluegrass (Poa annua L.) is an extremely problematic weed in turfgrass, posing a significant challenge for turfgrass management. Injudicious use of herbicides for controlling this weed has led to resistance issues and environmental concerns. Site-specific weed control offers an opportunity to achieve effective weed control with less herbicide use, but it requires the development of a pipeline for weed detection and localization, as well as a path planning algorithm (PPA). To achieve this, unmanned aerial system (UAS)-based RGB imagery of P. annua plants in bermudagrass [Cynodon dactylon (L.) Pers.] turf was collected at different weed growth stages at two locations in Texas: Deer Park and College Station. A convolutional neural network (CNN) You Only Look Once (YOLO11) and a real-time detection transformer (RT-DETR) model were evaluated for weed detection. The results showed that the YOLO11n model achieved the highest F1 score (0.64) and mean average precision (mAP)@0.50 (0.68), while the RT-DETR-x model achieved the lowest F1 score (0.52) and mAP@0.50 (0.51). The GeoTransform function transforms image coordinates into a world coordinate system with centimeter-level accuracy (mean error = 1.5 cm). However, the precision of the transformation depends on the quality of the orthophoto georeferencing. Additionally, the PPA showed a significant reduction (37.7%) in travel distance compared with the original weed model–derived distance. The research highlighted the potential of UAS-based imagery for weed detection and localization in turfgrass. Further improvements are needed to enhance model performance by modifying the model architecture (e.g., input image size, hyperparameters) and evaluating its robustness across different weed growth stages and turfgrass species.

Palmer amaranth (Amaranthus palmeri S. Watson) is among the most problematic weeds in U.S. rowcrop systems. In furrow-irrigated rice (Oryza sativa L.) (FIR), which is typically produced within soybean [Glycine max (L.) Merr.]- and corn (Zea mays L.)-dominated landscapes in the U.S. Midsouth that contain preexisting resistant seedbanks, the absence of continuous flooding allows season-long weed emergence, while effective postemergence control options remain limited. Iptriazopyrid, a novel azole carboxamide 4hydroxyphenylpyruvate dioxygenase (HPPD)-inhibitor under development for use in rice, possesses a chemical structure distinct from triketones such as mesotrione. Whether this structurally different HPPD-inhibitor endows altered susceptibility to metabolic resistance mechanisms in A. palmeri remains unknown. Therefore, the objectives were to evaluate the postemergence efficacy of iptriazopyrid and to compare its parent compound depletion with mesotrione in known mesotrione resistant (MSR2) and mesotrione-susceptible A. palmeri accessions (1986 and/or 21–115). Dose–response experiments showed that iptriazopyrid maintained consistent efficacy across accessions, with no significant differences among estimated response parameters. In contrast, mesotrione required 2.83- to 9.21-fold higher rates in MSR2 to achieve responses comparable to those observed in the susceptible 1986 accession. Quantification of parent compound over time revealed limited depletion of iptriazopyrid across accessions, with >95% of the parent compound remaining up to 12 h after treatment in all three accessions and approximately 75% remaining at 24 h in MSR2. Conversely, mesotrione underwent rapid metabolism in MSR2, declining to 18% of the parent compound by 8 h and to <6% by 24 h, indicating that resistance mechanisms conferring reduced sensitivity to mesotrione in MSR2 do not similarly compromise iptriazopyrid. Therefore, iptriazopyrid may provide an effective postemergence option for managing A. palmeri in FIR, including mesotrione-resistant populations, and may help diversify herbicide programs and reduce selection for metabolic resistance in U.S. Midsouth cropping systems.

Encapsulated saflufenacil uses a solid-phase encapsulation, which is different from traditional herbicide encapsulations. Saflufenacil is released following dry conditions that allow the microcapsule to fracture. Thus, encapsulated saflufenacil is not available for foliar uptake using standard application methods. A trace amount of non-encapsulated saflufenacil remains in the formulation from an incomplete purification process and may cause foliar phytotoxicity from postemergence applications. Experiments were conducted using relative photosystem II (PSII) efficiency of corn (Zea mays L.) leaf tissue to determine encapsulated saflufenacil bioavailability and to characterize saflufenacil microcapsule release under extended solution storage time. To evaluate injury potential, non-encapsulated, free saflufenacil was separated from the encapsulated formulation using microfiltration. An open-capsule treatment was created by allowing the encapsulated formulation to dry and then resolubilizing the herbicide. Relative PSII efficiency of the free, open-capsule, and encapsulated saflufenacil formulations were compared over 48 h after treatment (HAT). By 48 HAT, dry and non-encapsulated saflufenacil reduced relative PSII efficiency greater than the encapsulated saflufenacil, indicating that saflufenacil was not released from the encapsulation unless it underwent a period of drying. Furthermore, the reduced relative PSII efficiency was similar for the encapsulated and free saflufenacil, corroborating that the level of phytotoxicity from foliar encapsulated saflufenacil applications originates from the trace levels of free saflufenacil in the product. Saflufenacil microcapsule stability was evaluated following mixing with water and storage for 0, 1, 3, 5, or 7 d. Phytotoxicity did not increase with extended storage times, as the reduction in relative PSII efficiency from 0 to 48 HAT remained mostly constant across solution storage times. Overall, this research substantiates that saflufenacil encapsulation works to reduce foliar injury and documents the encapsulation durability under extended storage in water solution.

Biodiversity plantings are effective methods of enhancing on-farm biodiversity. However, farmers are often hesitant to place them adjacent to crop fields due to concerns that they may harbor problematic weeds and pest arthropods or that the intentionally planted species may escape into the crop and act as weeds. The objective of this research was to compare weed and arthropod communities in planted versus conventionally managed field margins at two sites in New York State. Planted treatments were seeded with either native wildflowers or grasses and then either mowed infrequently or unmanaged after planting. Conventional field margin management treatments included infrequent and frequent mowing, glyphosate application, and an unmanaged control. Measurements included both seedbank and aboveground plant density and diversity, plant biomass, and the abundance of both beneficial and pest arthropods. Pest arthropod abundance both in the margin and in the crop was not affected by the field margin management strategy. Arthropod abundance and plant richness and diversity, both within fields and field margins, were not strongly affected by the field margin management method. Once the plantings were established, weed density was lower within planted margins than conventionally managed margins (P = 0.0002), with a difference of 92.8% per 0.5 m2 in 2025. Treatment affected weed biomass (P = 0.002), but treatment means differed significantly at only one site in 2024 according to Tukey’s honestly significant difference. Overall, our results indicate that the establishment of field margin plantings is unlikely to exacerbate weed pressure from field margins.

Weed management is a primary barrier to sustainable organic vegetable production, and reducing the germinable soil weed seedbank is a critical long-term strategy for alleviating weed pressure. This study evaluated the effect of cover crops established in alleyways or traffic pathways on germinable warm-season weed seedbank density, species composition, functional group structure, and temporal emergence dynamics during transition to certified organic vegetable production. Treatments included three grass–legume cover crop bicultures of perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.), orchardgrass (Dactylis glomerata L.)–red clover (Trifolium pratense L.), sorghum-sudangrass [Sorghum × drummondii (Steud.) Millsp. & Chas]–white sweet clover [Melilotus officinalis (L.) Lam.], and a tilled fallow control. In the third year of the study, soil samples from cover-cropped and tilled fallow control pathways were subjected to a 60-d greenhouse emergence bioassay with observations recorded at 15, 30, 45, and 60 d after greenhouse setup. All three cover crop treatments reduced total germinable weed seedbank density by 73% to 82% relative to the tilled fallow, with no significant differences among cover crop treatments. Suppression was driven primarily by reductions in the annual broadleaf and annual grass functional groups, with carpetweed (Mollugo verticillata L.) and foxtail (Setaria spp.) identified as the principal species suppressed. Weed species richness did not differ among cover crop treatments or between cover crop treatments and the tilled fallow control. The tilled fallow produced a highly concentrated early emergence flush, with approximately 88% of total seedlings emerging within the first 15 d, whereas cover crop treatments substantially reduced and redistributed emergence across the monitoring period. Perennial ryegrass–white clover exhibited the most delayed peak emergence timing among all treatments. These findings demonstrate that traffic pathway cover cropping effectively suppresses the readily germinable warm-season weed seedbank during organic vegetable transition, with both annual and perennial cover crop bicultures providing equivalent suppressive benefits.

Crystalline ice plant [Cryophytum crystallinum (L.) N.E. Br.] is a succulent plant indigenous to South Africa. It is a highly invasive weed in North America. There are currently three weevil species from the native range that show promise as potential biological control agents for invasive populations in North America. The present study used a ddRADseq (double digest restriction site–associated DNA sequencing) population genetic technique to match the invasive populations in North America to their source of origin to prioritize survey areas where the best-matched agent genotypes are likely to occur. We found that populations in the Canary Islands and Morocco closely matched those in the invaded North American range and that this genetic cluster was most similar to the South African native range sites surrounding the Cape Town area and those from Aniston Village farther east along the coastline. There was evidence of an invasion route from South Africa to the Mediterranean Basin, with a secondary bridgehead invasion that likely took place from there to North America. Genetic structuring within the native range revealed a total of four distinct populations, where sites north and south of Cape Town were unique and did not match the invasive populations. We found a unique outlier population in the Northern Cape that displayed intermediate morphological traits between C. crystallinum and its close relative, ice plant (Mesembryanthemum guerichianum Pax; syn.: Cryophytum guerichianum Pax). Surveys for biological control agents should focus on the areas between Kalk Bay and Yzerfontein in the Western Cape and sites surrounding Arniston Village.

Sticky nightshade (Solanum sisymbriifolium Lam.) has emerged as a significant invasive weed across agricultural and natural ecosystems globally. The species contains toxic steroidal glycoalkaloids that pose a risk to livestock. Furthermore, its ability to form dense infestations can reduce the abundance of desirable plant species and hinder management of both natural and agricultural systems. Despite its increasing impact, information on its germination ecology and seedling emergence behavior remains limited. A series of laboratory and glasshouse experiments were conducted to investigate the effects of temperature, light, pH, salinity, moisture stress, and burial depth on the seed germination and seedling emergence of S. sisymbriifolium. Results showed that germination was highest (85.5%) under diurnally alternating temperatures of 35/15 C, while light had no significant effect. Seed germination was 74.1% to 84.7% across a wide pH range (4 to 10), indicating minimal sensitivity to pH variation. Germination declined sharply with increasing salinity and was completely inhibited at 125 mM NaCl. Similarly, germination decreased from 85.1% to zero as osmotic potential declined from 0 to −0.80 MPa, indicating that S. sisymbriifolium requires sufficient moisture for successful germination. Seedling emergence was greatest (72.4%) at a burial depth of 2.5 cm and declined significantly at greater depth. Overall, this study demonstrates that S. sisymbriifolium can grow in a broad range of environmental conditions but is sensitive to moisture stress, salinity, and deeper burial. This ecological flexibility may facilitate its spread across diverse habitats. These findings provide useful guidance for designing more efficient and sustainable integrated weed management strategies to reduce germination and seedling emergence of this invasive species.

The increased adoption of early-planted soybean [Glycine max (L.) Merr.] has required investigation of the persistence of commonly used residual herbicides under colder soil temperatures. Controlled environment and field studies evaluated the persistence of chlorimuron-ethyl, flumioxazin, and pyroxasulfone in Indiana soils (Wanatah [sandy loam, pH 6.2, 1.5% OM], Lafayette [silt loam, pH 6.6, 2.5% OM], and Butlerville [silt loam, pH 5.9, 1.6% OM]). A controlled environment bioassay assessed the effects of soil properties and incubation temperature on flumioxazin and pyroxasulfone persistence using velvetleaf (Abutilon theophrasti Medik.) as the indicator species. Results indicated greater persistence of both herbicides under colder soil conditions. Flumioxazin persistence increased in soils with higher organic matter, while pyroxasulfone persistence was greater in soils with higher pH. Field studies conducted in 2024 and 2025 evaluated herbicide persistence following applications at soybean planting dates from late March to early June in Wanatah and Lafayette soils. Herbicide concentrations were quantified using chemical extraction and ultra-high performance liquid chromatography. In Wanatah soil in 2025, the early planting date, characterized by colder temperatures and lower precipitation, resulted in 45% higher flumioxazin and 25% higher pyroxasulfone concentrations at 30 d after planting (DAP) compared with the later planting date. However, in 2024, increased precipitation following early May planting reduced herbicide persistence relative to late May applications. In Lafayette soil, early May applications resulted in 77%, 35%, and 21% higher concentrations of chlorimuron-ethyl, flumioxazin, and pyroxasulfone, respectively, at 30 DAP compared with mid-June applications. These findings indicate that earlier planting dates can increase herbicide persistence under cooler and drier conditions, potentially extending the weed control window and increasing the risk of crop injury. However, extended residual weed control and the risk of crop injury under early planting conditions are limited by cumulative rainfall after application.

Carolina geranium (Geranium carolinianum L.) infestation is a concern for Florida strawberry [Fragaria × ananassa (Weston) Duchesne ex Rozier (pro sp.) [chiloensis × virginiana]] producers. Current control measures rely on hand weeding or clopyralid applications when the weed is small. Unfortunately, early detection tends not to occur due to occlusion by the canopy. Coordinating postemergence control with emergence timing could improve control. Therefore, the objective of this study was to model the cumulative emergence of G. carolinianum in the row middles and transplant holes on the plastic-mulched beds of Florida strawberry fields using accumulated growing degree days (GDD) (thermal or hydrothermal time) as a predictive variable. A 7-yr study was conducted in two strawberry fields within Hillsborough County, FL, for row middles and a 2-yr study was conducted for bed tops. Emergence was modeled as a function of accumulated standard and restricted GDD. The model was calibrated using 5 randomly selected site-years of data and validated with 2 additional site-years for row middles, while only calibration was done for bed tops. Annual variation in emergence timing was driven by both temperature and moisture in the row middles, whereas emergence on the bed tops was influenced by temperature alone. Incorporating restrictions on GDD accumulation reduced overestimation of GDD and improved model prediction (standard GDD model with adjusted R2 = −0.10, RMSE = 37.31; restricted GDD model with adjusted R2 = 0.90, RMSE = 11.46) and enhanced the model’s applicability for row middles over space and time. In contrast, no improvement in model performance was observed for the bed tops. Emergence began simultaneously, but 50% and 90% cumulative emergence occurred at least a week later on bed tops compared with row middles. Overall, G. carolinianum primarily emerged from mid-October to mid-December, which allows implementation of control measures before harvest initiation.

Burning nettle (Urtica urens L.) and common groundsel (Senecio vulgaris L.) are widespread, economically important weeds in horticultural systems. This laboratory and glasshouse study evaluated the effect of temperature, photoperiod, salinity, osmotic stress, and pH on seed germination, and the effect of burial depth on seedling emergence of these species. A significant interaction between temperature and photoperiod showed that germination depended on combined thermal and light cues rather than either factor alone. Urtica urens had higher germination in complete darkness (53%) than in light/dark (3%) across three temperature regimes studied. Germination peaked at 90% at 25/15 C in complete darkness, while no germination occurred for this species at 15/5 C and 35/25 C day/night temperatures. In contrast, S. vulgaris preferred light/dark conditions (52% germination vs. 29% in darkness), reaching 96% at 25/15 C under day/night conditions. Salinity and osmotic stress inhibited germination of both species in a nonlinear, sigmoidal pattern. Germination of U. urens was completely inhibited at ≥200 mM of sodium chloride (NaCl) and at ≤ −0.6 MPa osmotic potential. Senecio vulgaris showed greater tolerance, with complete inhibition at ≥250 mM NaCl concentration and at ≤ −1.0 MPa osmotic stress. Germination of U. urens peaked at pH 6 (92%) and declined under more acidic and alkaline conditions, while S. vulgaris germinated >97% across all pH levels (4 to 10). Urtica urens showed overall low emergence, with 11% from soil surface and <1% when buried at different depths. In contrast, S. vulgaris showed up to 90% and 38% emergence from surface in sand and soil, respectively, but its seeds could not emerge beyond 0.5-cm burial depth. These findings can help refine integrated weed management in baby leaf crops by identifying periods when emergence is most likely, supporting timely stale seedbed or preemergence interventions, avoiding unnecessary soil disturbance when conditions favor germination, and prioritizing surface-focused control tactics for S. vulgaris.

Asiatic dayflower (Commelina communis L.) has recently emerged as a problematic species in dry direct-seeded rice (Oryza sativa L.) (DDSR) systems in China. Understanding its germination and emergence ecology is essential for developing effective integrated weed management strategies. However, information on the effect of diverse environmental factors on its germination and emergence ecology remains limited. This study evaluated the germination ecology of C. communis in response to temperature, light, osmotic stress, salinity, radiant heat exposure, wheat residue cover, and seed burial depth. Seeds failed to germinate at 20/10 C, whereas germination was initiated at 25/15 C (62%) and was highest at 35/25 C and 40/30 C (96% to 98%), regardless of light conditions. A three-parameter sigmoid model predicted 50% inhibition at −0.23 MPa osmotic potential and complete inhibition at −0.8 MPa. At increasing sodium chloride (NaCl) concentrations, 50% inhibition occurred at 191 mM NaCl, with complete inhibition at 350 mM NaCl, suggesting moderate salinity tolerance. Exposure to radiant heat (≥160 C for 5 min) completely inhibited germination, suggesting that residue burning may be an effective control measure. Seedling emergence was greatest (91%) on the soil surface but declined sharply with increasing burial depth, with no emergence observed beyond 13 cm. Increasing wheat residue reduced seedling emergence, with significant reductions observed at higher residue rates (notably 6 and 10 Mg ha⁻1). These findings offer crucial insights into C. communis germination ecology and have practical implications for its integrated management in DDSR systems. They also provide an ecological framework for optimizing the timing of weed control, seedbank management, and tillage practices in Chinese DDSR systems.

Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is one of the most problematic weeds in Kerala rice (Oryza sativa L.) ecosystems because of its morphological similarity to rice and its potential to cause substantial yield losses. This study evaluated integrated cultural weed management strategies by examining the effects of seed burial depth, flooding depth, and rice straw mulch on weed emergence and seedling vigor. Surface-sown seeds recorded the highest emergence, whereas burial at 1 cm reduced emergence by 84%, with negligible emergence (<1%) at burial depths of 6 to 8 cm. Flooding significantly suppressed weed establishment, with a water depth of 5 cm reducing emergence by 75% and seedling biomass by 83%, while depths of ≥6 cm completely inhibited emergence. Rice straw mulch also effectively reduced weed emergence by 50% or more at application rates of 6,000 to 8,000 kg ha−1 and completely prevented emergence at 10,000 kg ha⁻1. Correlation analysis revealed significant negative relationships between seed burial depth, flooding depth, mulch rate, and weed emergence and seedling vigor. Regression analysis showed significant negative linear relationships between seedling biomass and both seed burial depth and mulch rate, and between seedling length and these factors, whereas the response to flooding depth was best described by a significant quadratic model. Integrating deep tillage or the stale seedbed technique with appropriate water management in wet direct-seeded rice or rice straw mulching (6,000 to 10,000 kg ha⁻1) in aerobic and rainfed upland rice, can suppress E. crus-galli emergence and growth by 80% to 100%, providing a sustainable alternative to herbicide-based weed management.

In the wild blueberry (Vaccinium angustifolium Aiton) system, perennial weeds are a significant challenge. Weeds compete for resources and have a patchy, heterogeneous distribution, often growing among the rhizome of the crop. Producers broadcast spray herbicides to control weeds, but currently seek to lower costs, reduce environmental impact, and mitigate herbicide resistance. Site-specific weed management (SSWM) using weed maps offers a targeted solution, but its adoption is limited by the lack of software compatible with commercial spray equipment and by technological constraints, such as weed patch size thresholds. The objective of this work is to suggest new weed-mapping workflows for ground and drone spraying in wild blueberry fields using RGB drone imagery processed in drone-compatible GIS software: PIX4Dfields. Drone aerial imagery from two commercial wild blueberry fields in Maine was captured in May 2025. To create maps for ground spot spraying, PIX4Dfield’s machine learning-driven “Magic Tool” and five vegetation Index Tool workflows were assessed. For drone zone spraying, maps created with minimum weed patch sizes of 9.3 m2 and 405 m2 were evaluated. All maps were validated using image-based and ground-based accuracy assessments. The “Magic Tool” workflow proved most effective for ground spray maps, achieving ≤98% (image-based) and ≤86% (ground-based) overall accuracy. Among the vegetation indices, the Triangular Greenness Index performed best (≤93% and ≤85% image-based and ground-based accuracies, respectively) at a 20% to 25% pixel exclusion level. For drone zone spraying, the 9.3-m2 minimum weed patch size yielded higher accuracy than the 405-m2 size, although performance was site dependent. Classification accuracy decreased at sites with greater weed species diversity, more uniform weed distribution, and when evaluated against more reliable ground-based reference data. Nevertheless, the resulting maps identified weed coverage ranges of 39% to 52% and 58% to 61% across the two fields, giving growers a practical tool to reduce inputs and implement SSWM.

Common lambsquarters (Chenopodium album L.) is one of the most troublesome weeds in Atlantic Canadian potato (Solanum tuberosum L.) production systems. A high proportion of C. album in this region has been identified as resistant to commonly used herbicides and has become increasingly difficult to control with existing management practices. Atlantic potato producers have adopted cover crops into their rotations for soil conservation and nutrient cycling benefits, as well as suppression of crop pests, including weeds. Four cover crops and termination methods were evaluated for their ability to suppress C. album populations in a potato rotation at Harrington, PE, and Fredericton, NB, from 2018 to 2020. Brown mustard [Brassica juncea (L.) Czern.], buckwheat (Fagopyrum esculentum Moench), timothy (Phleum pratense L.), and a mixture of hairy vetch (Vicia villosa Roth), annual ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot], and crimson clover (Trifolium incarnatum L.), were spring sowed and terminated by mowing, roller-crimping, disking, or glyphosate in fall. Effects of cover crops and termination methods were consistently greater at Fredericton than at Harrington and were attributed to lower initial C. album seedbank density. Buckwheat and brown mustard cover crops established rapidly and reduced C. album densities in the subsequent potato crop by greater than 46%. Termination via disking and glyphosate improved marketable yields, yet the soil incorporation through disking buckwheat maximized the weed suppressive effects and reduced the germinable fraction of the C. album seedbank by 64% when compared with glyphosate. Our results highlight the importance of the starting seedbank density on the success of weed management tactics, where higher initial weed seedbank density can hinder the success of cover crop establishment in potato rotations. Further, these results verify the importance of proper cover crop selection for managing the seedbank in potato rotations and reduce the impact of herbicide-resistant weeds on production systems.

Resurgence of weedy rice (Oryza spp.) poses a growing threat to California rice production due to its high genetic diversity, seed dormancy, seedbank persistence, and lack of registered herbicides for in-season control. Cultural methods like fall tillage and winter flooding may offer control. Therefore, outdoor experiments were conducted in Colusa County, CA, from 2019 to 2021 to evaluate the effects of winter flooding (no flood vs. 10-cm flood), burial depth (2-cm shallow vs. 6-cm deep), and duration (30, 60, 90 d) on seed mortality and dormancy of four weedy rice biotypes (B1, B2, B3, and B5) in comparison with a commercial rice cultivar (‘M-206’). Flooding had no significant main effect in 2019 but increased overall mortality in 2020 to 2021 (24% no flood vs. 32% flood). Shallow burial (41%) produced greater mortality than deep burial (28%) in 2019; this pattern reversed in 2020 to 2021 (deep 30%, shallow 26%). Burial duration increased mortality from 19% (30 d) to 46% (90 d) in 2019 and from 13% to 44% in 2020 to 2021. Flooding increased M-206 (38% to 62%) and B2 (25% to 34%) mortality in 2020 to 2021, reduced B1 mortality (13% to 7%, indicating anaerobic protection), and reversed direction for B3 and B5 between year strata. Under no-flood conditions, B1 (65%) and B5 (82% in 2019) mortality peaked at 90 d under shallow burial; flooding suppressed this depth effect. Year effects were substantial, with 2019 producing consistently higher mortality coinciding with subzero minimum air temperatures (−0.5 to −2.8 C) within the first three burial days and above-average precipitation. Flooding-induced secondary dormancy was restricted to B1 (deep burial) in 2019; in 2020 to 2021, M-206, B1, B2, and B3 showed the same response, but B5 did not. These biotype-specific responses confirm that winter management strategies must be tailored to weed population composition.

This study addresses the distribution of wild carrot [Daucus carota (L.) ssp. carota], in the hybrid carrot seed [Daucus carota (L.) ssp. sativus (Hoffm.) Arcang.; hereafter Daucus carota] production region of central Oregon. Field surveys conducted in 2022 and 2023 in collaboration with regional partners provided observational data to train a relative risk model (random forest). Integrating 75 known D. carota occurrences, more than 2,000 known absences, and 1,000 randomly generated background points with data on topography, climate, soil, road proximity, and land cover, the model effectively distinguished potential D. carota establishment sites, achieving a high predictive accuracy (AUC = 0.911) against a background dataset. We identified four model-probability cutoff values (using precision–recall F-measure, varying alpha parameter), yielding five risk categories, from very low to very high risk. The moderate to very high risk categories highlight priority areas for monitoring and management to mitigate the risk of D. carota establishment, a concern especially relevant for local hybrid carrot seed production given the potential for cross-pollination and genetic contamination. The resulting risk maps provide a spatially explicit framework for identifying environmentally suitable habitats and potential invasion corridors, supporting early detection and rapid response efforts. By focusing surveillance and management activities within high-risk areas, stakeholders can improve monitoring efficiency, reduce the likelihood of D. carota establishment and spread, and help maintain the genetic integrity of central Oregon’s hybrid carrot seed production system.

The rapid adoption of spray drones in agriculture has outpaced the scientific research needed to support their effective and safe use. While current research on spray drones has examined parameters like flight speed, flight height, application rate, and droplet sizes, the combined effects of spray width and droplet size settings remain unstudied, especially for spot spray applications. This study employed a three by three randomized complete block design to evaluate deposition and drift responses using a DJI Agras T40 drone. Water-sensitive cards were sprayed with water in a single pass under three spray width settings (3.0, 4.6, and 6.1 m) and three droplet size settings (220, 280, and 340 µm). Wider spray widths (4.6 and 6.1 m) and larger droplet size settings (340 µm) significantly increased application volume observed on water-sensitive cards, reflecting higher flow rates and lesser susceptibility of droplets to downwash effects. Increased flow rates reduce centrifugal nozzle spin, which resulted in significantly larger average droplet diameters at the 6.1-m setting. Effective swath width (ESW) measurements varied by method. The bilateral method produced the widest ESWs, whereas the 50% deposition and ESW30 methods produced ESWs at or below intended spray widths. Despite uniform droplet distribution (diameter variation coefficient <20%), substantial drift occurred, extending up to eight times the intended spray width. Overall, our data suggests that increasing spray width settings to 4.6 m and 6.1 m and droplet size settings to 340 μm improved deposition and reduced drift due to greater droplet sizes; however, programmed settings did not consistently reflect field outcomes. This shows the need to (1) account for high drift potential in prescription mapping, (2) conduct field calibrations to optimize ESW selection and overlap, and (3) modify flight plans and spray formulations to better align programmed and actual spray performance.

The genus Conyza comprises globally important weeds, with horseweed [Conyza canadensis (L.) Cronquist; syn.: Erigeron canadensis L.], hairy fleabane [Conyza bonariensis (L.) Cronquist; syn.: Erigeron bonariensis L.], and Sumatran fleabane [Conyza sumatrensis (Retz.) E. Walker] repeatedly evolving resistance to multiple herbicide modes of action. This review provides an updated comparative synthesis of resistance evolution, resistance profiles, and mechanistic drivers among these three species. The earliest documented resistance cases occurred in both C. canadensis and C. bonariensis around 1980, including resistance to paraquat and photosystem II (PSII) inhibitors. Resistance subsequently expanded to glyphosate and, more recently, to multiple-herbicide resistance. Concerning resistance profiles, comparative analysis reveals species-specific patterns: C. canadensis has the largest number of reported resistance cases; C. bonariensis has evolved resistance to a broad range of herbicide modes of action; and C. sumatrensis exhibits some of the most complex multiple-resistance profiles, with populations resistant to up to five herbicide modes of action. Resistance dissemination has been facilitated by inheritance of resistance traits, gene flow, and, where documented, hybridization. Regarding mechanistic drivers, evolutionary trajectories involve both target-site (TSR) and non–target site resistance (NTSR) mechanisms. TSR typically arises through target-site mutations or increased target-site abundance. In contrast, NTSR is linked to altered herbicide transport, sequestration, and detoxification. ATP-binding cassette (ABC) transporter activity, cytochrome P450 monooxygenases, glutathione S-transferases, glycosyltransferases, and antioxidant enzymes may contribute to reduced herbicide sensitivity in some populations. These adaptations compromise long-term herbicide efficacy and highlight the limitations of herbicide rotation alone. The findings provide a mechanistic framework for predicting future resistance evolution and support integrated weed management strategies that reduce selection pressure and improve the sustainability of weed management.