The root parasitic weed branched broomrape [Phelipanche ramosa (L.) Pomel] spends most of its life cycle underground, complicating early detection and control. A predictive model based on growing degree days (GDD) can improve management by anticipating key developmental stages. This study aimed to characterize P. ramosa phenology and develop a thermal time model to inform more effective control strategies. Two greenhouse experiments using rhizotrons were conducted over two years (2021–2022), along with a complementary pot experiment in 2022 at Davis, CA. The P. ramosa development was classified into four phenological stages: attachment, elongation, emergence, and full flowering. We recorded the thermal timing (GDD accumulation from transplanting) and number of individuals at each phenological stage and modeled the development dynamics using an inverse Weibull function. Of the 255 P. ramosa attachments recorded across two rhizotron runs, 87% advanced to elongation, 63% reached emergence, and only 49% successfully developed to full flowering. Model estimates indicated that 5% of attachments occurred at 299 GDD and 95% by 730 GDD, marking a critical control window. After the initial attachment, on average, it took about 85 GDD for an attachment to initiate the elongation process, and 385 and 815 GDDs to reach 5% and 95% elongation, respectively. Emergence followed, with 5–95% occurring from 520 to 1100 GDD. Full flowering occurred roughly 181 GDD after emergence, spanning 700 (5%) to 1280 (95%) GDD after transplanting. Model validation using data from related field experiments conducted in 2022 and 2023 in a P. ramosa-infested tomato (Solanum lycopersicum L.) field in Yolo County, CA, confirmed the model’s accuracy in predicting full flowering with Root Mean Square Error (RMSE) of 142 GDD. This thermal time model offers a valuable decision-support tool to optimize the timing of P. ramosa management, particularly in-season soil-applied herbicide programs, in tomato cropping systems.

Weed pressure threatens lentil (Lens culinaris Medik.) yields, with metribuzin offering control but risking crop injury. This study used hydroponics to screen metribuzin tolerance in lentils, determining the lethal dose 50% (LD50) for lentil cultivar, CDC Greenstar and profiling metabolites in three genotypes VIR421 (susceptible), CDC Greenstar (tolerant), and NZ2022 (medium-tolerant) via liquid chromatography-mass spectrometry (LC-MS). CDC Greenstar plants in a hydroponic deep-water culture system were exposed to metribuzin doses (0.17, 0.25, 0.51, and 2.05 g a.i. ha⁻¹, plus a control) selected based on preliminary trials that identified the effective range for LD50 estimation in hydroponics, where herbicide bioavailability is higher than in soil due to direct root exposure and absence of soil adsorption. These doses are substantially lower than the recommended field application rate of 205 g a.i. ha⁻¹ as a pre-emergence for lentils to account for the amplified effects in hydroponics for 24 hours, with biomass reductions assessed over 21 days. The LD50 was 0.4407 g a.i. ha⁻¹ (R2 = 0.94), with dose strongly reducing shoot/root growth (r = -0.92 to -0.99). Untargeted LC-MS identified seven metabolites in CDC Greenstar and VIR421, including desamino-metribuzin (DA) and conjugates, while targeted LC-MS tracked metribuzin, DA, and desamino-diketo-metribuzin (DADK) over 12 days. VIR421 had higher metribuzin levels (105.70 ng/g at dry weight at 12 h) compared to CDC Greenstar and NZ2022, which rapidly metabolized it to DA (58 and 50.41 ng/g dry weight at 2 days), with NZ2022 showing further metabolism by 4 days. DA dominated 59 to 167-fold over DADK, suggesting a primary detoxification pathway. Hydroponics enabled precise tolerance screening, revealing genotype-specific metabolism critical for breeding metribuzin-tolerant lentils, enhancing weed management strategies.

Improving herbicide efficacy under drought stress is essential for improving weed management and limiting the associated challenges. Leaf water content (LWC), a vital eco-physiological trait, can be used to indicate drought stress and improve herbicide efficacy. To investigate how water stress-induced changes in LWC affect glyphosate efficacy across diverse weed types, broadleaf weed Santa Maria feverfew (Parthenium hysterophorus L.) and narrow-leaf giant foxtail (Setaria faberi Herrm.) were selected. A controlled greenhouse study was conducted with two treatment factors including three moisture levels (well-watered at 100% WHC, moderate drought at 75% WHC, and severe drought at 50% WHC) and glyphosate doses (0, 180, 360, 540, 720 and 900 g a.e. ha⁻¹). Drought stress significantly reduced LWC and stomatal conductance in both species, while the reduction in LWC was more pronounced in P. hysterophorus (26%) than in S. faberi (23%), the reduction in stomatal conductance was severe and similar for both species (82% and 83%, respectively). Severe drought stress drastically reduced shikimic acid concentration (41-59%) in both species. Severe drought stress significantly reduced glyphosate efficacy, suppressing mortality by up to 63% and biomass reduction up to 58%. Shikimic acid concentration and weed mortality both showed a strong positive correlation with change in LWC under all tested water stress levels. Glyphosate applications when LWC falls below 70% resulted in poor weed control at recommended field rates. Therefore, LWC can be used as a real-time predictive biomarker to monitor drought stress, schedule irrigation prior to glyphosate application, optimize the dose and ultimately improve its efficacy.

Bentazon, a photosystem II-inhibiting postemergence herbicide, has been used in corn (Zea mays L.), beans, wheat (Triticum aestivum L.), and vegetables to manage common lambsquarters (Chenopodium album L.), although growers have reported reduced efficacy across the country. The aim of this study was to describe the sensitivity response of C. album to bentazon and identify whether reported escapes could be considered as cases of herbicide resistance evolution. We evaluated C. album populations collected from lima and snap bean (Phaseolus vulgaris L.) fields across Delaware, Illinois, Minnesota, New York, and Oregon. Dose-response experiments with 25 populations were conducted to create a reference response to bentazon, using rates that ranged from 0 to 8,406 g ai ha-1. Injury ratings and biomass were assessed 28 days after herbicide application, and the herbicide rates required to reduce growth by 50% (I50 or GR50) and 80% (I80 or GR80) were calculated. Results indicated C. album responses to bentazon varied within and across states. Across all populations studied, the GR50 for biomass reduction ranged from 159 to 816 g ai ha-1, and GR80 from 230 to 1,944 g ai ha-1 with populations from Oregon exhibiting the highest average GR50, followed by those from New York, the Northcentral states, and Delaware. Based on our criteria that the injury rating- or biomass-based resistance index (ratio between I50 or GR50 of the suspected-resistant and a local selected susceptible population) had to be at least two, and the I80 or GR80 should be greater than the labeled field rate, one population from New York (NY6) and one from Oregon (OR29) were considered as resistant. This research underscores the wide variation in C. album response to bentazon across the U.S., the importance of herbicide resistance diagnostic strategies that account for local population variation, and highlights the increasing challenge of C. album management in specialty crops.

Understanding weed community structure is essential for designing sustainable integrated weed management (IWM) strategies in perennial fruit systems. This study aimed to characterize the floristic composition, abundance, and spatial structure of weed communities in jackfruit (Artocarpus heterophyllus Lam.) orchards across Vinh Long province, Vietnam. Field surveys were conducted during the main rainy season of 2023 using systematic quadrat sampling across multiple agroecological zones. A total of 35 weed species in 18 families were recorded, with Poaceae being the most dominant family (10 species, 28.6%), followed by Asteraceae and Cyperaceae (4 species each, 11.4%). Quantitative metrics including density, mean field density (MFD), relative MFD, cover, and multiplied dominance ratio (MDR) identified a consistent group of dominant species: Ludwigia octovalvis (Jacq.) P.H.Raven, Ageratum conyzoides L., and Axonopus compressus (Sw.) P.Beauv., while sedges such as Fimbristylis quinquangularis (Vahl) Kunth also contributed significantly. Hygrophilous species such as Peperomia pellucida (L.) Kunth, Centella asiatica (L.) Urb., and Pouzolzia zeylanica (L.) Benn. showed high mean occurrence field density (MOFD), whereas A. conyzoides and L. octovalvis dominated relative MFD, indicating adaptation to high-light environments. Diversity indices (Margalef’s richness, Shannon’s H′, Pielou’s evenness, and Simpson’s dominance) differed modestly among agroecological regions. Ordination analysis grouped species along a gradient primarily associated with density and cover. Similarity indices (Jaccard and Sørensen) were uniformly high (mostly >0.75), suggesting strong species overlap between regions. Notably, community composition shifted with orchard age, with older orchards exhibiting less species mixing. Weedy rice (Oryza sativa f. spontanea) was detected but was relatively infrequent. These findings provide a quantitative baseline for designing integrated weed management strategies in perennial fruit systems. Specifically, the results support a transition away from routine herbicide use toward ecologically based practices such as mowing before flowering and selective suppression of high-importance weeds, tailored by orchard age and site conditions.

American sloughgrass [Beckmannia syzigachne (Steud.) Fernald] is a troublesome wheat weed. We tested the germination of B. syzigachne seeds under different temperatures with growth chambers (12 h dark/12 h light, 12000 lx), simulating those during the sowing periods of early- (25/15 C), ordinary- (20/10 C), late- (15/5 C), and very late-sown winter wheat (5/0 C). We also tested the accumulated temperatures required for seedling growth to the 2- to 5-leaf stages, using 225 populations collected from wheat fields in eastern China. The average 1000-seed weight of the 225 populations was 1.2 ± 0.01 g. Overall populations tested did not show seed germination after 21 days of treatment (DAT) at 5/0 C or constant 30 C. At 14 DAT with 25/15 C, 20/10 C, and 15/5 C, the mean germination rates were 85.4%, 6.4%, and 0.1%, respectively. These rates increased to 99.9%, 58.6%, and 21.7% at 21 DAT. Populations collected from lower latitude regions germinated significantly faster (P < 0.05) under optimal conditions. Accumulated temperatures required for growing the 2nd, 3rd, 4th, and 5th leaf were 139.0 ± 1.0, 127.8 ± 1.0, 115.6 ± 1.0, and 98.9 ± 0.7 C, which showed a significant decreasing trend. The narrower optimal temperature range for B. syzigachne seed germination and higher thermal requirements for early seedling growth constrain its distributions, while the heterogeneous seed germination facilitates its infestations in wheat planting areas in eastern China.

Pollinators are susceptible to insecticide residues when foraging on weedy flowers in turfgrass systems. Deterrent practices may mitigate this risk by reducing pollinator visits; however, their effectiveness in limiting contact exposure of pollinators has not been thoroughly evaluated. Two trials were conducted using a randomized complete block design with three temporal blocks to assess the effectiveness of deterrent practices in preventing contact exposure of actively trapped honey bees (Apis mellifera) and passively trapped insects to fluorescent powder-treated white clover (Trifolium repens L.) inflorescences in turfgrass. Deterrent treatments included mowing the same morning before fluorescent powder application, spraying with a premix of 2,4-D, MCPP, and dicamba two d before powder treatment, or no deterrent before powder application. Fluorescent powder was extracted from 1,440 honey bee specimens collected by active trapping at 4 and 28 hours after treatment. Mowing and synthetic auxin herbicides pre-treatment reduced the number of fluorescent powder-exposed honey bees by at least 75% and 93%, respectively. Among exposed honey bees, mowing and herbicide treatments reduced powder concentration by at least 75% and 90%, respectively. Honey bee visitation was positively correlated with T. repens inflorescence density, explaining 81% of visitation variability. Mowing transiently decreased T. repens floral density by 85%, but recovered by 7 d, while herbicides resulted in complete loss of floral resources by 7 d. Blue vane traps captured 1,117 bees from 23 species, over 96% of which were native, while yellow sticky cards collected 384 insects from the Lepidoptera, Diptera, and Coleoptera orders. Despite differences in honey bee exposure, deterrent treatments did not affect the exposure of passively trapped pollinators to fluorescent powder, likely due to strong visual attraction of traps. Results suggest that mowing and synthetic auxin herbicides effectively deter honey bees from T. repens inflorescences, reducing their exposure risk.

To address the complexity and excessive reliance on expert experience in tuning fuzzy Proportional-Integral-Derivative (PID) controller parameters, this study proposes a variable-rate spraying control system that integrates an improved Beetle Antennae Search (IBAS) algorithm with fuzzy PID control. To evaluate the feasibility of the system, a mathematical transfer function of the variable-rate spraying system was constructed, and a flow control simulation platform was established for simulation analysis. To overcome the limitations of conventional BAS, which is prone to premature convergence and limited search precision, the IBAS algorithm was developed. The improvements include a hybrid disturbance strategy to enhance individual search capability and a simulated annealing mechanism to prevent the algorithm from being trapped in local optima. Using the IBAS algorithm, the proportional and quantization factors of the fuzzy PID controller were optimized offline to obtain the optimal parameters. The IBAS-fuzzy PID controller was then compared in simulation with conventional PID, fuzzy PID, and BAS-optimized fuzzy PID controllers. The simulation results demonstrated that the IBAS-fuzzy PID algorithm achieved higher flow control accuracy than existing methods. To further validate the effectiveness of the improved algorithm under practical conditions, field experiments were conducted. The results indicated that the IBAS-optimized fuzzy PID controller outperformed the three other control methods in terms of flow control accuracy. Overall, both simulation and field results confirm that the proposed IBAS algorithm for fuzzy PID parameter optimization significantly enhances response speed, control precision, and overshoot reduction, providing a novel approach and potential application for variable-rate spraying technology.