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Abstract Background Napropamide is used to control annual grasses and broadleaf weeds. It affects root and shoot development. However, its mechanism of action is inconclusive and hence is classified in group 0 herbicides by the Herbicide Resistance Action Committee (HRAC). Objective This study focused on exploring specific endpoints which could decode some fundamental aspects leading to the inhibitory effect of napropamide on plants. Methods For rapid in vitro evaluation of morphological parameters, root and shoot length in tomato plant was measured using the International Organization for Standardization (ISO) compliant phytotox system. Indole acids were measured by Salkowski’s method and LC-MS/MS and the role of key genes involved in auxin transport was studied with qPCR. Results In this study, napropamide treatment inhibited root length by 67.6% at 50 μM, on day 8. Total indole acids content using colorimetric analysis was 13.2 ± 0.9 μg mL-1 in treated plants with respect to 10.2 ± 0.9 μg mL-1 in control. Detailed LC-MS/MS analysis revealed IAA levels to be 88.8 ± 16.2 ng mL-1 and 31.3 ± 6.1 ng mL-1 and indole butyric acid (IBA) levels to be 55.2 ± 3.4 ng mL-1 and 27.7 ± 2.5 ng mL-1 in treated and untreated plants respectively. In line with these observations, major auxin transporters AUX1/LAX, PINs showed upregulation of 1.9 to 3.6 folds upon napropamide treatment. Conclusion This study highlights the effect of napropamide on auxin levels and gene expression and presents a rapid, simple, and user-friendly model for studying inhibitory effect of herbicides in plants.

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Abstract Background Horseweed (Conyza bonariensis) is an important weed species infesting soybean plantations. Some biotypes with multiple herbicide resistance have been recently reported. One way to avoid weed dispersion and spread to adjacent areas is by reducing and preventing seed germination. Objective We aimed to evaluate the effects of auxinic herbicides (2,4-D, dicamba, triclopyr and halauxifen-methyl), with or without mixing with glyphosate, on the production, germination and morphology of horseweed seeds. Methods With the recent release of the transgenic soybean event DAS-44406-6 in Brazil, we conducted three experiments with different horseweed biotypes (Canguiri, Palotina and Palmeira) and application stages (early and late vegetative, and early reproductive). Results Auxinic herbicides, applied alone or mixed with glyphosate, reduced the germination and production of horseweed seeds, regardless of the stage of application. The application of herbicides caused morphological changes in the seeds, such as darkening, damaged achenes and papillae, and absence of embryos. Conclusions For plants that produced seeds, there was a 100% reduction in germination, showing that the application of these herbicides can be a viable strategy in the integrated management of this species.

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Abstract Background Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv.) is an annual weed affecting many field crops. A glyphosate-putative-resistant barnyardgrass population was found from a soybean field in southern Brazil. Objective This study aimed to confirm this resistance in Rio Grande do Sul (RS) and identify its mechanism. Methods Dose-response curves were generated using a three-parameter nonlinear regression model to assess control efficacy and shoot dry weight reduction. Resistance factors (RF) were calculated across two generations from the resistant (BR20Esp016) and susceptible (BR19Esp001) populations. cDNA was synthesized from total RNA extracted from the plants, and the EPSPS gene was sequenced from both populations. Results Based on the glyphosate required to reduce dry weight by 50% (GR50), the resistance biotype had RFs of 2.4 and 2.6 and values of 2.4 and 13.9 for the same variable for the self-fertilization generation (F2). A mutation was detected in the EPSPS gene, where proline (CCA) is replaced by alanine (GCA) at position 106, conferring resistance to EPSPS-inhibiting herbicides in barnyardgrass. Conclusion Glyphosate resistance in the barnyardgrass biotype BR20Esp016 is due to target-site resistance associated with a mutation in the EPSPS gene.

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Abstract: Background Herbicide-resistant E. crus-galli poses a significant threat to rice production in direct-seeded rice systems. Objective This study aimed to confirm the presence of bispyribac-sodium-resistant (R) E. crus-galli and determine the optimal mixture ratio of propanil and quinclorac to control the R biotype. Methods E. crus-galli seeds from putative resistant and susceptible biotypes were collected from rice fields located 10 km apart in Alor Setar, Kedah, Malaysia, and screened with bispyribac-sodium, propanil, and quinclorac. Dose-response tests were conducted to confirm herbicide resistance. Propanil and quinclorac were tank-mixed at ratios of 20:80, 40:60, 60:40, and 80:20 and their inhibitory effects were evaluated under glasshouse conditions. Results Dose-response tests showed a 128-fold increase in the resistant biotype (R) compared to the susceptible (S) biotype based on the dosage corresponding to 50% inhibition of shoot growth, and a 70-fold increase based on the dosage that caused 50% mortality. The mixture ratios of propanil and quinclorac exhibited synergistic action except for the 80:20 ratio, which was antagonistic. The 40:60 mixture ratio outperformed the others, allowing the rates of propanil and quinclorac to be reduced by 2.2 and 4.7-fold, respectively, compared to their single applications to achieve 95% mortality. Conclusions: Dose-response tests revealed a high resistance level in the R biotype to bispyribac-sodium. Propanil and quinclorac at recommended rates were effective in controlling the R biotype. This study demonstrates that the ratio of propanil in combination with quinclorac is crucial in enhancing the herbicidal activity.

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Abstract Background Pistia stratiotes L., is an invasive aquatic plant that forms dense mats, disrupting ecosystems and affecting waterway navigation. Although various control methods have been studied, there is no clear consensus on the best approach. Objective The goal of this study is to evaluate the efficacy of various control methods in managing P. stratiotes infestations. Methods Laboratory trials tested the efficacy of diquat, d-limonene, mineral oil, and potassium salts of fatty acids on P. stratiotes. Treatments were applied at concentrations from 10–30%, with weekly monitoring for five weeks to assess treated plants visual quality (injury symptoms), and dry biomass. Greenhouse trials replicated the most effective laboratory treatments. Results In laboratory trials, diquat at 0.89% achieved > 90% reduction in visual quality and dry biomass of P. stratiotes, making it the most effective treatment. D-limonene at 30% showed similar efficacy, while mineral oil also significantly reduced P. stratiotes populations. Combinations of d-limonene with mineral oil or potassium salts of fatty acids exhibited synergistic effects; some combinations achieved >90% reduction in visual quality and dry biomass. Treatments prepared with seawater with diquat (0.89%) and d-limonene (20% and 30%) were the most effective treatments. Greenhouse trials confirmed these results, suggesting these treatments could be effective. Conclusions In conclusion, this study underscores the effectiveness of diverse strategies in controlling P. stratiotes infestations. Further research is warranted to evaluate long-term efficacy, cost-effectiveness, and environmental impact. Integrated approaches offer a multifaceted and sustainable solution for managing P. stratiotes, mitigating its ecological and economic impacts.

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Abstract Background Herbicide exposure affects the agro-histological characteristics and seed production of barnyardgrass in lowland rice fields. Objective This study aimed to assess the impact of the 2,4-D dimethylamine on the agro-histological and seed production of barnyardgrass and its effects on lowland rice plants. Methods Barnyardgrass seeds were collected from lowland rice fields in nine sub-districts of Serdang Bedagai District, Indonesia. The study was conducted in farmer fields in Medan Selayang, Indonesia, from August to December 2022. The study used a randomized block design with a single factor, 40 populations of barnyardgrass sprayed the 2,4-D dimethylamine at 1.5 fold of the recommended dose (1,080 g ai ha-1) with three replications. Results The increase in tissue size of the upper epidermis, mesophyll, and lower epidermis can be used as an indicator of the effect of higher doses of 2,4-D dimethylamine. The herbicide 2,4-D dimethylamine at a dose of 1.5 fold caused an increase in the seeds produced of barnyardgrass biotypes up to 8.20 fold and lowland rice yield until 5.98 tons ha-1. Conclusions The herbicide remained safe for the growth and yield of lowland rice and enlarge the agro-histological tissues of barnyardgrass.

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Abstract Background: Acacia auriculiformis (earleaf acacia), an Australian perennial tree, is an increasingly problematic invasive species in Florida. Objective: Create a host range molecular phylogeny by generating test plant patristic distances to earleaf acacia (using rbcL sequences). Methods: DNA was extracted and sequenced from 98 Fabaceae species and an additional 28 sequences were downloaded from NCBI. Results: Molecular phylogenetics and patristic distance inform which plant species should be tested starting with closely related (usually native) plants, especially those threatened or endangered, then extending to less related plants of commercial value. Conclusions: We show the Mimosoideae clade, while monophyletic, appears within the Caesalpinioideae clade. We also suggest 33 mostly threatened or endangered species for the initial test list from the Mimosoideae and Caesalpinioideae, including nine Papilionoideae commercial species. Finally, as a secondary test list, if additional testing is required, we suggest 30 additional Papilionoideae species be added.

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Abstract Background: Understanding the interactions between weed communities and chickpea crops can improve weed management practices, boost crop productivity, and promote sustainability. Objective: Assessing the interference caused by weed communities on chickpea production and to explore the relationship between weed biodiversity and chickpea yield. Methods: Random sampling was utilized to assess weed populations in 85 chickpea fields. Weed density and canopy cover, as well as indices of species richness, Shannon-Weiner, and Camargo's evenness, were recorded at two phenological stages of chickpeas: four to seven leaves and mid to early-podding. Regression methods were employed to examine the effects of weed traits on chickpea yield. Finally, principal component analysis was conducted among weed and chickpea data. Results: Chickpea yield decreased with increasing weed density and canopy cover. Increasing weed density from 0 to 50 plants m-2 decreased chickpea yield by 36.73% at the four to seven-leaf stage. In addition, an increase in canopy cover from 0 to 55% caused a yield loss of 41.70 g m-2 at the early-podding stage. Wild safflower (Carthamus oxyacantha M. Bieb.) and chicory (Cichorium intybus L.) were the most predominant weeds with a significant negative correlation with chickpea yield. Licorice (Glycyrrhiza glabra L.) had a negative correlation with chicory and wild safflower. There was a positive relationship between density and canopy cover of licorice and chickpea yield, weed diversity and evenness. Conclusions: Effective weed management should focus on both controlling dominant species and promoting weed diversity to enhance crop productivity and environmental sustainability.

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Abstract Background: Swallowwort (Cynanchum acutum subsp. sibiricum) poses significant challenges in cotton fields and orchards across northwest China. Objective: Laboratory and greenhouse experiments were conducted to investigate the impact of various abiotic factors on seed germination of swallowwort. Methods: Seed germination and seedling emergence of freshly harvested seed (FS) and seed stored for six months (SS) were investigated under different temperatures, osmotic potentials, saline stresses, and burial depths. Results: The optimal germination temperature of FS was 30 to 35 °C, while that for SS was extended to 15 to 35 °C. Freshly harvested seeds germinated under alternating temperature regimes from 20/10 to 45/35 °C, but seed germination could reach to 60% at 15/5 °C after six months of storage. No germination of FS was observed at ≤ -1.0 MPa. However, seed germination remained at 44.6% at -1.0 MPa after storage. Saline stress reduced seed germination, with no germination observed at NaCl concentrations of ≥ 400 mM for the FS or ≥ 500 mM for the SS. However, pH values ranging from 5 to 10 had no significant impact on seed germination. The maximum seedling emergence (71%) was observed at the soil surface and no emergence at 10-cm burial depth. Conclusions: Six months of storage enhanced seed tolerance to sub-optimal temperature, drought and salt stress conditions, comparing with FS. This made swallowwort more adaptable to harsh environments such as drought and salinity. Therefore, timely weed control is necessary to prevent seed production.

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Abstract An alternative for the control of weedy rice (Oryza sativa) and barnyardgrass (Echinochioa spp.) resistant to imidazolinone herbicides are acetyl coenzyme-A carboxylase inhibitors (ACCase) herbicides used in cultivar tolerant to these compounds. The objective was to evaluate the interaction of propaquizafop in tank mix with herbicides used in rice tolerant to ACCase inhibitors to control weedy rice and barnyardgrass. Two experiments were conducted, in the 2022/2023 season, in Dom Pedrito and Formigueiro. The hybrid XP739MA (MaxAce® technology) was used at both locations. The treatments were arranged in a 3x8+1 factorial design with factor A being rates of propaquizafop (0, 125 and 180 g ha-1), and factor B tested herbicides carfentrazone, propanil, quinclorac, penoxsulam, florpyrauxifen-benzyl, bentazon, saflufenacil, and untreated control. The additional treatment was two applications of propaquizafop (125 g ha-1). The analyzed variables were weedy rice and barnyardgrass control, rice injury, yield components and yield. The interactions were mostly additive for weedy rice and barnyardgrass control. The antagonism of the tank mixture of propaquizafop with quinclorac and florpyrauxifenbenzyl for barnyardgrass and with propanil for weedy rice reduced the yield components in Dom Pedrito. The interactions of propaquizafop with propanil were antagonistic and resulted in the lowest yield in Formigueiro. For this tank mix at the highest propaquizafop rate, yield decreased 14.6% more than at the 125 g ha-1 rate. Tank mix of propaquizafop with other herbicides used in tolerant rice with MaxAce® technology can be used, increasing the weed control spectrum.

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Abstract: Background Johnsongrass (Sorghum halepense (L.) Pers.) is one of the most problematic weeds worldwide, and in recent years, control failures with herbicides inhibiting the enzyme acetolactate synthase (ALS) have been reported. Objective Determine the resistance in different biotypes of Johnsongrass to nicosulfuron, as well as elucidate its possible resistance mechanism. Methods Dose-response bioassays were conducted with four biotypes, three of them from corn fields with consecutive history of nicosulfuron applications (Veracruz-Mexico) and a susceptible biotype (Guanajuato-Mexico). A partial sequence of the ALS gene was obtained for each biotype to identify mutations conferring target-site resistance to this herbicide. Results The dose-response curves showed high rates of resistance in the biotypes from Veracruz (IR: 30, 63, and 77 times more resistant than the susceptible biotype); at the molecular level, a mutation was found, which resulted in the substitution of amino acid (Asp376Glu). Conclusions This mutation could be involved in resistance in the Oro Verde, El Marcial, and Francisco Villa populations.

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Abstract Background Field dodder is a parasitic plant that continues to pose a significant challenge to both agricultural systems and natural ecosystems. Objective This experiment sought to evaluate some control methods for field dodder, assess their impact on eggplant growth, and analyze isothiocyanate content in arugula and black radish through GC-MS. Methods The experiment evaluated some control methods for managing field dodder, including arugula and black radish as cover crops, with and without mulch, and mulch alone. Two controls were used: one with and one without a field dodder. The key measurements included the number of infected plants, field dodder biomass, and control efficiency. Additionally, eggplant growth, yield, and losses were assessed, and GC-MS analysis identified isothiocyanate compounds in arugula and black radish. Results The control efficiency against field dodder in eggplant found to be 96% for arugula combined with mulch, 92% for black radish combined with mulch, 91% for mulch, 68% for arugula, and 63% for black radish. The arugula combined with mulch treatment had the highest positive impact on yield, producing 83.96 tons per hectare. Uncontrolled field dodder caused 82% yield loss, a 31% reduction in plant height, and a 59% decrease in fruit number. GC-MS analysis showed that arugula had the highest isothiocyanate content, comprising 36.23% of the total peak area of compounds detected in the sample, while black radish contained 29.20% isothiocyanates based on the same measure. Conclusions Arugula and black radish are alternative control methods for field dodder when incorporated into the soil to reduce the seed bank.

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Abstract Background Echinochloa crus-galli is a weed that has developed resistance to multiple herbicides. In Ecuador, the selection pressure caused by the continued use of the acetolactate synthase-inhibiting herbicide bispyribac-sodium would have favored the selection of resistant accessions. Objective The current study aimed to analyze the sensitivity to bispyribac-sodium of E. crus-galli populations collected in the province of Guayas, the main rice-growing region of Ecuador. Methods A total of 35 E. crus-galli populations were assessed. These were sprayed with bispyribac-sodium at a commercial dose of 40 g a.i. ha-1. The four most resistant accessions and the most susceptible population were submitted to dose-response curves. Data were adjusted using a log-logistic model and the mean lethal dose (LD50) for each population was calculated. Finally, response of the populations to the herbicide and their interaction with malathion, a cytochrome P450 monooxygenase inhibitor, was studied. Results Seventy-two percent of the 35 accessions showed poor to deficient control (<70%) by bispyribac-sodium. Neither population showed 100% mortality in response to the recommend dose the herbicide. The LD50 values for the R populations were at least 16.1 times higher than those for the S population. The interaction of bispyribac-sodium with malathion indicated that, for at least one of the R populations, resistance may be determined by xenobiotic metabolism. Conclusions E. crus-galli populations collected from rice fields showed high level of resistance to bispyribac-sodium, even at the highest doses evaluated.

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Abstract Background The primary challenge in Malaysian vegetable farms is the herbicide resistance in E. indica. Objective: This study aimed to assess herbicide resistance in E. indica biotypes on a cucumber farm in Penang, Malaysia. Methods Seedlings of the putative resistant and susceptible biotypes were propagated and transferred into seedling trays containing peat moss. The seedlings were subjected to premix of diuron and MSMA, glufosinate, glyphosate, oxyfluorfen, napropamide, quiazlofop and clethodim treatments at the three-to-four-leaf stage. Results Dose-response tests showed that the resistant biotype was 15-fold, 12-fold, 80-fold, and 2-fold more resistant to glyphosate, clethodim, quizalofop, and the diuron plus MSMA premix, respectively, compared to the susceptible biotype based on herbicide rates which caused 50% reduction in shoot dry weight. However, both biotypes were susceptible to glufosinate, oxyfluorfen and napropamide treatments. Conclusions The findings have confirmed multiple herbicide resistance in goosegrass to glyphosate, clethodim, quizalofop, and premix of diuron and MSMA.

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Abstract: Background: In recent years, artificial intelligence methods based on image processing have been introduced for weed identification therefore weed control. Image processing methods typically cause a heavy computer workload. Objective: The goal of this research was to create a classification model for weed development stages with better accuracy reduced workload by incorporating Region of Interest (ROI) into existing classification models. Methods: Weeds were grown and photographed in several development stages for the dataset. Using the ROI technique, commonly utilized in medicine, the leaf image features were digitized, and a total of 448 sample records were obtained. Of these image features, 9 were identified as the most important variables using the linear regression model. SMOTE analysis was applied to balance the distribution in our data. The data were randomly divided into 70% for training, 15% for testing, and 15% for validation groups. The models were developed by using artificial intelligence methods such as ANFIS, MLPNN, SVM, kNN, Naive Bayes, Decision Tree, Random Forest, Deep Learning, and Logistic Regression. Results: Accuracy, Precision, Recall, and F1-score parameters were used to evaluate the performance of the models. NB, ANFIS, and LR models failed to produce results within acceptable limits. However, RF, MLPNN, DT, Keras, and SVM models were successful. kNN models results were not far off but a failure nonetheless. Conclusions: Based on these results, we demonstrated that our RF, MLPNN, DT, Keras, SVM, and kNN models with ROI implementation can successfully determine the development stages of weeds.

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Abstract Background: Hairy beggarticks (Bidens pilosa L.) is a highly adaptable weed species that thrives in diverse environmental conditions. Understanding the environmental factors that influence its germination is essential for developing predictive emergence models and supporting integrated management strategies. Objective: The present study aimed to estimate the cardinal temperatures and water potentials for B. pilosa germination, assess seed bank longevity, and develop a field-based emergence model. Methods: Laboratory experiments were conducted to determine base temperature and water potential thresholds for seed germination. Eight temperatures (10, 15, 20, 25, 30, 35, 40, and 45 °C) and 10 water potentials (0, −0.05, −0.1, −0.2, −0.4, −0.6, −0.9, −1.2, −1.5, and −2.0 MPa) were tested. Field experiments were conducted from 2014 to 2018, with seedling emergence monitored under three sowing conditions. To assess seed bank longevity and persistence, a factorial experiment was set up using three burial depths (0, 3, and 6 cm) and five seed retrieval times (0, 1, 4, 10, and 16 months). Results: The base, optimal, and maximum temperatures for seedling emergence were 10.4, 24.7, and 41.9 °C, respectively. The base water potential was −0.85 MPa. Thermal and hydrothermal models were adequate to predict the emergence of hairy beggarticks at different soybean sowing dates. The species forms a transient seed bank; however, the greater burial depth was associated with increased seed longevity (16 months) in the soil. Conclusions: The models are able to predict emergence under the evaluated conditions, and deeper seed burial was associated with longer seed bank longevity.

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Abstract: Background: Alligatorweed (Alternanthera philoxeroides) is an invasive weed species whose increasing infestations challenge sunflower production under climate change settings. Objective: Evaluate the impact of A. philoxeroides at different competition durations on nutrient accumulation and sunflower production, and determine the critical period of weed competition (CPWC). Methods: Two-year yield study was executed with treatments including A. philoxeroides competition durations i.e. weed free conditions for first 21, 28, 35, 42 and 49 days after crop emergence along with a full season weed free treatment and conversely weedy conditions for the first 21, 28, 35, 42 and 49 days after crop emergence along with a full season weedy treatment (90–100 days). Results: Weed infestation caused significant accumulation of nutrients, weedy for full season caused more accumulation of macronutrients (N, P and K at 62, 48, 55 kg ha-1, respectively) and micronutrients (Cu, Fe, Mn and Zn at 19, 186, 137, 72 g ha-1, respectively). Full season weedy produced more weed biomass (2098 kg ha-1) and caused maximum reduction in achene (55%) and oil yield (50%) of sunflower. Four parameters log-logistic model revealed that A. philoxeroides infestation for 56.66 DACE and 64.49 DACE caused 50% achene yield loss in sunflower in 2020 and 2021, respectively. Further, model predicted A. philoxeroides competition for 4 DACE to 40.97 DACE and 6.36 DACE to 45.29 DACE as CPWC to cause 5% and 10% achene yield losses, respectively. Conclusions: Timely control of A. philoxeroides within the CPWC is crucial for mitigating yield losses and ensuring sustainable sunflower production. Furthermore, the nutrient accumulation potential of aquatic A. philoxeroides could potentially be harnessed for heavy metal accumulation, benefiting both aquatic and terrestrial ecosystems.

Resumo em Inglês:

Abstract Farmers use herbicide mixtures to increase the efficacy and spectrum of weed control during the pre-planting burndown stage of soybean. The efficacy of herbicides should be rigorously assessed, and digital tools have great potential for application during pre-planting weed management. This study aimed to evaluate the efficacy of weed control using herbicide mixtures and to test digital tools that analyze spectral responses as a means to assess efficacy. Two field experiments were set up, and the herbicides tested included diquat + carfentrazone-ethyl, glyphosate + 2,4-D, glyphosate + ammonium glufosinate, glyphosate + carfentrazone-ethyl, and glyphosate + clethodim. The main weed species identified were Urochioa piantaginea, Commeiina benghaiensis, Nicandra physaiodes, Ipomoea triloba, Portuiaca oieracea, Cyperus rotundus, Eieusine indica, and Aiternanthera teneiia. Efficacy for each species was assessed using a 0–100% scale for visual injury (VI). Each plot was evaluated using five methods: VI, Visible Atmospherically Resistant Index (VARI), Canopeo App, manual Greenseeker, and evaluation of images on a computer screen. The alternative methods were compared to the VI scores using Pearson correlation analysis. It was observed that, in general, the herbicides were less effective in controlling E. indica, C. benghaiensis, I. triioba, and A. teneiia. Control scores greater than 80% were recorded for U. piantaginea, N. physaiodes, and P. oieracea. Alternative methods can be used as additives or substitutes for herbicide efficacy assessments. Greenseeker generally showed a strong correlation with VI, and the efficacy of fast-acting products was more easily detected using alternative methods.

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Abstract Background: The changes in rice production systems, by soybean introduction, have created favorable conditions for Sumatran fleabane [Conyza sumatrensis (Retz.) E.Walker] to increase its potential to establish, spread, and impact crop yields in lowland areas. Objective: Therefore, this study to valuate the competitive ability of Sumatran fleabane on flooded and non-flooded rice. Methods: Two experiments were conducted in the greenhouse and repeated twice. The experiment was carried out with a completely randomized design, with four replications, testing two plant sizes for Sumatran fleabane (Factor A) (large and small plants), and Sumatran fleabane populations of 0, 35, 71, 141, and 282 plants per m2 (Factor B). The experiment was conducted under both flooded and non-flooded conditions for up to 45 days after rice emergence. Results: Under non-flooded conditions, there was a reduction in the number of leaves (about 45%), an increase in phyllochron (approximately 75 ºC day/leaf), reduction or absence of tillers, greater decline in shoot and root dry mass, an approximate 50% reduction in Haun scale, and up to 68% reduction in rice height. Under flooded conditions, there was no significant reduction in the number of leaves or in phyllochron. There was less impact on the number of tillers (reduction only at 282 plants m−2), smaller reductions in dry mass, and final values with little difference among Sumatran fleabane populations for Haun scale and height. Conclusions: Large plants of Sumatran fleabane are highly competitive, especially under non-flooded conditions. Flooding conditions reduces competition effects of Sumatran fleabane, regardless of the size.

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Abstract Background: Organic rice weed management can be addressed through winter cover crops (CC). In spring, rice is seeded, CC are terminated and the field is flooded. CC residues provide a mulching layer that can reduce weed emergence, but the degradation of the biomass may also reduce weed germination through the release of organic acids. Objective: The objective of the study is to evaluate the effect of flooding water after CC degradation on weed germination and emergence. Methods: The study included both field and greenhouse trials and lasted 2 years. CC were Italian ryegrass, hairy vetch and a mixture of both. In the field, water was sampled in two locations, 5 and 10 days after flooding, and used in germination tests on weedy rice (Oryza sativa). In the greenhouse, a simulation of the technique was performed in buckets filled with paddy field soil: some received the CC degraded water only, others had both the water and the CC mulch layer. Water was sampled after 7 days for germination trials and total weed density in the buckets was assessed. Results: The germination of weedy rice was not affected by the flooding water (>92.5%). Total weed density in the buckets was reduced only when the CC mulch was present. Conclusions: The flooding water sampled after the degradation of the cover crop biomass did not affect weedy rice germination, both in field and in greenhouse conditions. If the CC mulch is absent, the flooding water alone is not able to reduce weeds.

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Abstract: Background: Giant hogweed (Heracleum mantegazzianum Sommier and Levier) is a perennial herbaceous plant that can grow to a height of 2−5 m. A single flowering plant can produce more than 20,000 seeds. It is one of Europe's most widespread and problematic invasive alien species and a severe threat to native biodiversity. Glyphosate is widely used to control H. mantegazzianum. Decades of intensive herbicide spraying have led to environmental pollution, prompting a need to explore new methods to supplement or replace glyphosate. Objective: Non-chemical methods to control H. mantegazzianum were tested and compared with glyphosate application. Methods: In two infested locations in southeast Norway, we compared the efficacy of glyphosate applications with a combination of mechanical cutting of the flowering stem of H. mantegazzianum and hot water treatment (80 °C). Hot water or glyphosate was supplied by foliar application or injection into the root crown. Results: The best method to reduce cover and the number of H. mantegazzianum rosettes and seedlings was achieved with two foliar applications of glyphosate. Cutting the flowering stem and injecting hot water into the root crown was almost as efficient as glyphosate application. Cutting and foliar applications of hot water had the weakest efficacy. Despite the best control and significant growth of grasses after glyphosate treatment, relatively high percentage of bare soil remained in the plots afterwards, increasing the risk of erosion. Conclusions: Cutting and injection of hot water in the root crown may be a viable alternative to glyphosate application in areas where herbicides are undesirable.

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Abstract: Background: Using the biomass endpoint as a reference, the rates of change in the fluorescence parameters demonstrated how rapidly the photosystem II- inhibitor (PSII-inhibitor) bentazon; a mixture of PSII-inhibitors—phenmedipham, desmedipham, and ethofumesate (a very-long-chain fatty acid {VLCFA} inhibitor); and the acetolactate synthase inhibitor (ALS-inhibitor) nicosulfuron affected the plants. Objective: The objective was to investigate how fluorescence parameters (Fv/Fm, Area above the Kautsky curve, and Performance Index (PI)) responded prior to biomass harvest. Methods: Two greenhouse experiments were conducted with Amaranthus retroflexus plants as models. ED20, ED50, and ED80 parameters derived from log-logistic dose–response curves were estimated using meta-analysis to investigate inherent variability. Results: For PSII-inhibitors, either applied alone or in combination with a VLCFA-inhibitor, Fv/Fm exhibited a negative linear slope with herbicide dose. The intercepts were close to the theoretical 0.8, one to two days after spraying (DAS). At three to four DAS, the response to PSII, and PSII combined with a VLCFA-inhibitor could be described by a log-logistic dose–response curve. For nicosulfuron, the Fv/Fm parameter showed a slope of zero and an intercept close to 0.8 across all DAS. Area and PI were imprecise in assessing the EDx values. Meta-analyses indicated that, in some cases, the variability of EDx was too high for these parameters to be considered reliable endpoints. Conclusions: The variability of all fluorescence parameters, besides Fv/Fm, was too high compared to the biomass endpoint. The study emphasized that combining independent dose-response curve experiments and analyzing EDx-derived parameters is essential to capture the extent of dose-response variability.

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Abstract: Weedy rice (WR) is a major weed of cultivated rice (CR), particularly difficult to manage early on due to its morphological similarity to CR. Understanding its agronomic traits requires analyzing both quantitative and qualitative data, best addressed through multivariate analysis that capture the complexity and interrelationships among diverse traits beyond univariate methods. A study was conducted to characterize the agronomic traits of selected Philippine WR accessions from various provinces, identify key traits contributing to phenotypic variation, and classify WR accessions into distinct groups. The study evaluated 16 accessions, including 15 WR accessions and IR64 as the control. Plants were grown in a screenhouse, with each accession replicated 10 times in pots. Eighteen agro-morphological traits, including vegetative, structural, seed morphological, and phenological traits, were assessed. Analysis of variance revealed significant differences between WR and CR, and among WR accessions. WR was generally taller with longer culms than CR, though some accessions, such as WR7 and WR62, matched IR64 in height. Most WR accessions matured earlier than CR. Factor analysis on mixed data (FAMD) showed that 100-seed weight, days to flowering, panicle initiation, maturity, plant height, culm length, leaf length, and pericarp color contributed most to the variation. WR accessions were clustered into six groups based on flowering time, maturity, awn length, tiller count, leaf width, culm length, height, leaf length, and pericarp color. This study provides insights into the phenotypic diversity of Philippine WR accessions, offering a better understanding of trait relationships that can inform targeted weed management strategies.

Resumo em Inglês:

Abstract: Background: Weed management continues to be a significant challenge in agriculture due to extreme use of chemicals which have adverse effects on environment and human health. Objective: This study investigates the potential of magnetic fields as an innovative and effective technique for weed control, aiming to determine their efficacy in modulating weed germination characteristics. Methods: It was evaluated the impact of a static electromagnetic field on the germination behavior of two weed species—Chenopodium album and Echinochloa crus-galli—under both laboratory and field conditions. Key parameters measured included germination percentage, germination rate, and average germination time, with variations in magnetic field intensity and exposure duration systematically assessed. Additionally, regression analysis was conducted, yielding mathematical models with coefficients of determination between 0.86 and 0.98, and a multi-objective genetic algorithm was employed to optimize the treatment parameters. Results: Optimal magnetic treatment conditions were identified as 10 minutes at 25 mT for Chenopodium album and 7.22 minutes at 22.46 mT for Echinochloa crus-galli. The results showed that magnetic treatment increased the germination percentage by up to 14% in Echinochloa crus-galli and 21% in Chenopodium album, respectively. Although the laboratory experiments yielded robust predictive models, the outcomes observed under field conditions did not fully replicate the laboratory results, indicating a potential divergence in treatment efficacy between controlled and real-world environments. Conclusions: The findings underscore the need for species-specific and tailored magnetic treatment parameters in weed management. The promising laboratory results coupled with the partial validation in field conditions provide a foundation for further research into sustainable alternatives to conventional herbicides.

Resumo em Inglês:

Abstract Background: Purple nutsedge (Cyperus rotundus L.), a perennial C4 plant from the Cyperaceae family, is one of the most invasive weed species worldwide and significantly affects crop yields. Objective: To identify and validate stable reference genes (RGs) for reliable gene expression normalization in RT-qPCR analyses across various tissues of purple nutsedge. Methods: The expression patterns of 11 candidate RGs were evaluated across three tissue types, including tubers at three developmental stages forming tubers (FT), swelling tubers (ST), and mature tubers (MT), along with buds and leaves. Expression stability was evaluated using three widely accepted algorithms: geNorm, NormFinder, and BestKeeper. A consensus ranking (RK) was then generated using the RankAggreg package to identify the most stable RGs overall. Results: The most stable RGs varied across tissues. CrEF1α was optimal for FT, CrActin for ST, and CrADF7 for MT. For bud and leaf tissues, CrRPL11 and CrCYC showed the highest stability, respectively. Conclusions: This study demonstrates that the stability of RGs is tissue-dependent in purple nutsedge. The identified RGs provide a reliable basis for normalizing RT-qPCR data, enabling precise gene expression analyses in specific tissues such as tubers, buds, and leaves.

Resumo em Inglês:

Abstract: Background: Amaranthus spp., known as pigweeds, are aggressive weeds, which are highly competitive with soybean crops. Reports of biotypes resistant to the main mechanisms of action (EPSPs and ALS inhibitors) used for management make it essential to integrate new chemical control strategies. Objective: Assess the efficiency of dicamba and glyphosate and their association with residual herbicides (saflufenacil or flumioxazin), followed by glufosinate alone or combined with metribuzin, in controlling pigweeds resistant to EPSPs and ALS inhibitors, and the effect of phytotoxicity on the final yield of Xtend™ soybean. Methods: Two experiments were conducted in the 2021/22 (year 1) and 2022/23 (year 2) growing seasons, using a randomized block design with 15 treatments and four replications. The desiccation treatments were applied 15 days before soybean sowing (DBS) and pre-emergens one (1) day after sowing (DAS), as well as after crop emergence (V3/V4). Phytotoxicity, pigweed control, and final soybean yield were assessed. Results: Initial phytotoxicity, observed mainly via the application of associated pre-emergent herbicides, does not significantly damage the crop. Pigweed control was efficient when dicamba was associated with glyphosate, with sequential application of residual herbicides, especially flumioxazin, as well as glufosinate or glufosinate and metribuzin, in addition to the post-emergent application of fomesafen associated with glyphosate. Conclusions: Pigweeds resistant to EPSPs and ALS-inhibiting herbicides can be effectively controlled under management programs with sequential application of pre-and post-emergent herbicides in soybean, respecting application intervals.

Resumo em Inglês:

Abstract: Background Rising winter temperatures and increasing seasonal variability particularly during autumn and spring have contributed to the enhanced survival and proliferation of cold-tolerant weeds such as wild barley and feral rye in wheat fields. These resilient weeds compete aggressively with winter wheat and exhibit high adaptability to fluctuating environmental conditions. Objective This study aimed to evaluate the freezing tolerance of wheat, wild barley, and feral rye by assessing survival rates, electrolyte leakage, regrowth characteristics, and the maximum photochemical efficiency of photosystem II (Fv’/Fm’). Methods Plants were exposed to freezing temperatures (0, −3, −6, −9, −12, −15 and −18°C) in tillering stage and their tolerance was measured by determining the temperature at which 50% electrolyte leakage occurred in leaves (TEL50), the lethal temperature for 50% survival (LT50su), seedlings dry matter and Fv’/Fm’ at −18°C Results Feral rye exhibited the lowest TEL50 (−16°C), while wild barley showed the highest (−12°C). Wild barley also had the highest LT50su (−12.6°C), whereas feral rye had the lowest (−15.4°C). At −15°C, the reduction in dry matter for feral rye and wild barley was 33% and 84%, respectively. At −18°C, Fv’/Fm’ decreased by 65%, 70%, 76%, and 39% for wheat cultivars (Pishgam, Ghezel Khoushe), wild barley, and feral rye, respectively. Conclusions Rising winter temperatures may diminish wheat's capacity to withstand freezing stress, while more resilient species, such as wild barley and feral rye, may thrive. This shift could result in heightened competition and potential invasions in wheat fields due their natural adaptation to milder freezing conditions.

Resumo em Inglês:

Abstract: Background: Cuscuta species are generalist parasites of agricultural, ornamental, and wild species. For Mexico, there is a lack of comprehensive information about the host diversity of Cuscuta, models predicting the distribution of the species, and the use of molecular methods for detecting cryptic species. Objective: This study aimed to test if Cuscuta species have a high host diversity and broad potential distribution areas and show the utility of molecular methods for species identification. Methods: We reviewed herbarium specimens (recording species name, the Mexican state, coordinates, altitude, hosts, and vegetation). We estimated the distribution area for six Cuscuta species with > 30 independent georeferenced reports. Finally, we collected three Cuscuta aff. corymbosa specimens and identified them molecularly. Results: We found 2,533 records (56 species) of which Cuscuta corymbosa, C. tinctoria, and C. umbellata were the most frequent. Most of the 204 host species belong to Asteraceae, Euphorbiaceae, and Fabaceae. Of the six species modeled, those with the largest potential distribution areas were C. tinctoria and C. corymbosa. Molecular identification revealed that the specimens belong to three species, one unknown to the collection site (C. tolteca). Conclusions: Cuscuta species appeared in all Mexican states, but it is necessary to increase the collection because several neotropical states have an unexpectedly low diversity. Their potential distributions are broad, showing well-defined biogeographical affinities. Molecular methods reveal underestimation in Cuscuta diversity.

Resumo em Inglês:

Abstract: Background: Rice is one of the most important crops due to its importance in human nutrition and its multiple socio-economic contributions. Weeds are one of the main factors limiting rice production and have serious impacts. Objective: We aimed to identify the weed control practices of rice farmers, their problems with weeds and possible solutions to these problems. Methods: A survey (consisting of 41 questions) was conducted among 100 farmers in the Southern Marmara region of Türkiye. Chi-square test was used to test the relationship between the variables. In addition, information on the native and non-native status of weeds in the study area was compiled. Results: Almost all producers (92%) recognised the weeds they encountered. The most important were Echinochloa crus-galli and Echinochloa oryzoides (44%), Cyperus difformis (33%), Diplachne fusca (21%) and Paspalum distichum (2%). Integrated weed management (IWM) is generally not practiced (82%). Knowledge of IWM and the respondents’ education and experience are significantly correlated. All producers use herbicides and few practice herbicide rotation (17%). Cyhalofop butyl, oxadiazon, quinclorac, bentazon and imazamox were the most commonly used herbicides in the last three years. However, the perceived efficacy of some herbicides has decreased by 65% in the last three years. Conclusions: Farmers lack awareness of IWM practices and herbicide application procedures, but are aware of the possibility of herbicide resistance in weeds. Therefore, we present recommendations to contribute to filling the existing knowledge gap on weed precautions and management.

Resumo em Inglês:

Abstract Research on the uses of herbicide hormesis to improve crop yield and the role of herbicide hormesis in weed management has greatly increased in recent years. The use of herbicide hormesis to improve crop quality and yield has been hampered by erratic results and difficulty in choosing a dose that will provide reliable hormesis in the field. A sequential application of low glyphosate doses in the form of a seed treatment followed by a low dose after seedling emergence has been recently shown to provide more predictable hormesis in the field, resulting in significant increases in crop yield. However, herbicide hormesis can hamper weed management with herbicides in two ways. Recommended herbicide doses that overlap the hormetic dose range of some weeds can give them a competitive advantage. This is probably rare, but hormesis for weed subpopulations that are more tolerant/resistant than most of the plants in a weed population can accelerate the selection for and spread of herbicide resistance, a potentially more common phenomenon. The molecular mechanism(s) of herbicide hormesis is/are still unknown, other than mild stress triggering overcompensation, resulting in enhanced growth and reproductive processes. Glyphosate hormesis appears to be more consistent and pronounced than that with other herbicides. This may be due to large number of essential compounds produced by the shikimic pathway, compared to other herbicides and/or to its highly systemic mode of action.

Resumo em Inglês:

Abstract The Red Queen Hypothesis formulated by evolutionary biologist Leigh Van Valen describes how coevolving species are engaged in a continuous arms race. The hypothesis was inspired by Lewis Caroll’s novel “Through the Looking Glass” where the Red Queen says to Alice “Now, here, you see, it takes all the running you can do, to keep in the same place.” In this review we examine how climate change has heightened the arms race between crops and weeds and reflect on how these closely related entities are engaged in a race to adapt to climate change, which represents a serious threat to agricultural productivity. Weeds are adapting to climate change relatively rapidly, whereas crop evolution is restricted by traditional breeding programs to emphasize crop yields and genetic uniformity. Crops and weeds share much evolutionary history, with crops having been created by domestication of plant species which are often now classified as weeds. For example, in the case of rice, domestication resulted in a lack of infructescence shattering and seed dormancy. However, weedy rice which possesses both ancestral traits is now a serious pest of domestic rice, and continues to evolve, including developing traits for climate change resilience. We highlight the need to utilize knowledge of weed evolution and genomics in crop breeding, even to the point of incorporating genes from weeds as a possibility. Modern gene editing techniques must be utilized extensively to speed up crop improvement and help crops keep up to weeds in the Red Queen’s climate change race.

Resumo em Inglês:

Abstract: Background: Rangelands provide important ecosystem services, supported by the diverse flora of both weedy and native desirable plant species. Isatis tinctoria L., commonly known as dyer's woad, is one of the most important and common weeds that predominantly established in rangelands and has recently expanded into croplands, globally. The knowledge of the behaviour and management of this species has not been synthesized, curtailing further research and sustainable management. Objective: This review aims to provide extensive knowledge of the biology and ecology of I. tinctoria to highlight its growth traits, lifecycle, distribution, competition dynamics, invasiveness and different management options. Methods: In this paper, we have reviewed and discussed the available literature on various aspects of the biology and management of I. tinctoria. Results: Isatis tinctoria is highly competitive in nature, often forming dense stands which result in crop and pasture suppression and yield reduction in infested areas. The production losses associated with I. tinctoria infestations in rangelands have been estimated to be upwards of $ 2 million (USD) annually in the United States of America (USA), while such data are lacking from other parts of the world. Several control methods including preventive, chemical, cultural, and biological options have shown varying degree of success against this weed. Biological control agents such as Puccinia thlaspeos and Aulacobaris fallax in rangelands have been introduced in the USA. However, the efficacy of these biological control options varies. Conclusions: An integrated approach using biological control in combination with cultural (for rangelands) or chemical control (for agricultural areas) could be feasible for controlling this weed.

Resumo em Inglês:

Abstract Eleusine indica (L.) Gaertn., commonly known as goosegrass, is one of the most troublesome weed species worldwide. In Brazil, the increasing number of herbicide-resistance cases, particularly to glyphosate, has made goosegrass the most agronomically significant weed species in the country. Given its rapid spread in recent cropping seasons, this review compiles current knowledge on goosegrass biology and herbicide resistance to support the development of more effective integrated weed management strategies. Successful control approaches must consider the species’ biological characteristics and the potential occurrence of herbicide-resistant populations in target areas. The adoption of preventive practices (e.g., cleaning machinery, purchasing seeds from certified companies), cultural practices (e.g., balanced fertilization, use of regionally cultivars, phytotechnical adjustments), and mechanical practices (e.g., mowing) can optimize the effectiveness of herbicides in controlling this weed. Chemical control of goosegrass should rely on pre-emergence herbicides, along with post-emergence products featuring different mechanisms of action, with sequential applications anticipated. Implementing integrated weed management systems offers the potential to mitigate the current losses and damage caused by goosegrass.