Resumo em Inglês:

Abstract: Background: Numerous studies have described junglerice (Echinochloa colona) competitiveness against crops, but its behavior concerning plant density as an outcome of intraspecific competition has not been well documented. Objective: This study aimed to characterize morphology based on population density and determine the degree of density dependence. Methods: Junglerice was grown in field conditions in a range of densities from 0.25 to 300 plants m-2. Plant height and width, tillering, aerial dry weight, seed weight, seed number, and hundred-seed weight were determined and related to growth habits by principal components analysis. The variables were fitted to the growth habits using a general linear model. Aerial dry weight, tiller number, seed number, and seed weight per plant (pl-1) and per area (m-2) were fitted to plant density using non-linear functions. Results: Plants exhibited prostrate habit at 0.25 plants m-2, semi-prostrate habit at 2-4 plants m-2, and erect habit at 35 plants m-2. Prostrate plants displayed a width of 196 cm, a height of 40 cm, 158 tillers per plant, and over 32,000 seeds per plant, whereas erect plants had an average width of 13.7 cm, a height of 114.5 cm, 10 tillers per plant, and approximately 1,700 seeds per plant. The aerial dry matter per area adhered to the law of constant final yield. In contrast, tiller number, seed number, and weight per area had a nonlinear dome-shaped relationship. Conclusions: Junglerice modifies its aerial structures according to population density, showcasing extensive morphological plasticity. This characteristic allows junglerice to adopt different growth habits.

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Abstract: Background: The resistance of grass weeds to herbicides is expanding in wheat fields. An effective strategy for managing herbicide resistance is to prevent the likelihood of resistance development spreading from field margins to within fields. Objective: This study was conducted to evaluate the resistance development in winter wild oat (Avena sterilis subsp. ludoviciana) populations collected from within fields and field margins of 11 winter wheat fields to the commonly used ACCase and ALS-inhibiting herbicides. Methods: Seeds of 22 A. sterilis subsp. ludoviciana populations were collected, both from field margins and within winter wheat fields. The seeds were grown in greenhouse, and the seedlings at the three- to four-leaf stage were treated with the recommended field rates of the following four herbicides, clodinafop-propargyl (CP), pinoxaden (PN), mesosulfuron+iodosulfuron (MI), and mesosulfuron+iodosulfuron+diflufenican (MD). Results: All populations from within fields evolved resistance to CP, but none showed cross-resistance to PN. Importantly, there were notable variations in CP and MI resistance, with less than half of the samples from within fields demonstrating higher resistance, while for the remaining populations no differences were observed between field-margin and within-fields samples. Contradictory trend was observed in response to MD, where around 70% of populations followed the trend for CP and MI, surprisingly, around 30% of populations exhibited opposite results. Conclusions: Overall, the incidence of herbicide resistance to CP, MI, and MD was more common in populations from within fields, suggesting stronger selection pressure. However, some field margin populations showed MD resistance, underscoring the need for weed control in field margins as a proactive resistance management strategy.

Resumo em Inglês:

Abstract: Background: In a prior study, Lasiodiplodia theobromae (Pat.) Griffiths and Maubl. and Bipolaris bicolor (Mitra) Shoemaker., were found to suppress the growth of Eleusine indica (L.) Gaertn, but limited information exists on their response to environmental factors and herbicides for integrated E. indica control. Objective: This study aimed to determine the tolerance levels of L. theobromae and B. bicolor to pH, temperature, photoperiod, relative humidity, and herbicides. Methods: The mycelia and conidia of L. theobromae and B. bicolor were exposed to a range of environmental conditions and herbicides in a controlled setting, including different levels of temperature (25, 30, 35 ⁰C), pH (4, 6, 8, 10), photoperiod (24 hours of darkness; alternating 12 hours of blue light followed by 12 hours of darkness; and alternating cycles of 6 hours of blue light and 6 hours of darkness), and relative humidity (75, 85, 95%). Herbicides such as topramezone, diuron, oxyfluorfen, and imazethapyr were applied at their recommended rates. Conidial germination was assessed by counting after an 18-hour incubation using a haemocytometer, while the diameter of mycelium growth was measured after 3 days of incubation, except for the herbicide effects evaluation, which were extended over 7 days. Results: Laboratory assays demonstrated that L. theobromae exhibited higher conidial germination of 85-95% and superior mycelial growth under varied pH, temperature, and photoperiod conditions compared to B. bicolor. Lasiodioplodia theobromae's mycelia remained unaffected by herbicides at full labelled rates, but they inhibited the conidial germination of the fungus. For B. bicolor, the conidia were not affected by imazethapyr and topramezone, but its mycelial growth was reduced by imazethapyr, oxyfluorfen, and diuron. Conclusions: These results indicate that the mycelia of L. theobromae presents a more favorable option for tank mixing with test herbicides, offering potential for the formulation of an integrated control strategy against E. indica.

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Abstract: Background: Farmers often use glyphosate for cost-effective land clearance to streamline coffee harvest processes despite recommendations against its application near the harvest period. However, as set by national and international regulatory authorities, this practice poses a high risk of exceeding the maximum residue limit (MRL) for glyphosate in coffee beans. Objective: In this study, glyphosate residues in green coffee beans were assessed, considering different herbicide application methods (mechanical or manual), nozzles (hooded or unhooded), application volumes, and ripening stages. Methods: Coffee beans were collected between 15 to 60 days before harvest, and glyphosate residues were determined by high-efficiency liquid chromatography and mass spectrometry (LC-MS/MS). Results: Mechanical and manual applications using a protective spray bar device, avoiding the lower third of the coffee trees, maintained glyphosate residue levels within the MRLs established by Brazilian (1.0 mg kg−1) and European (0.1 mg kg−1) regulatory authorities. In contrast, applying glyphosate with the TK-VS-02 nozzle (high-flow impact) without a protective device resulted in levels below the Brazilian MRL but exceeded importing countries’ requirements. These residue levels persisted even when applications occurred outside the recommended rainy season but within the 15-day minimum safe re-entry interval. Applications using TK-VS-02 or AI11002 (low-flow air-induced) nozzles targeting the lower third of trees resulted in high glyphosate residue levels, surpassing national and international MRLs, even when applications were conducted 60 days before coffee harvest. Conclusions: These findings emphasize the importance of employing the right application technology to produce coffee that complies with the MRLs of any regulatory authority.

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Abstract Background Sowing dates and weed management practices could alter several phenological phases of direct seeded rice. However, limited is known about the impacts of these aspects on phenology, thermal efficiencies, and agro-meteorological indices of direct seeded rice. Objective The objective of the study was to evaluate the effect of sowing dates and weed management strategies on phenology, thermal efficiencies, and agro-meteorological indices of direct seeded rice. Methods Two sowing dates [10th May (early) and 3rd June (late)] and six weed management strategies [i.e., weedy-check, 4-time mechanical weeding (weed-free), bensulfuron methyl + pretilachlor as pre-emergence, oxyfluorfen as pre-emergence, bensulfuron methyl + pretilachlor as pre-emergence + 2,4-D as post-emergence, and oxyfluorfen as pre-emergence + 2,4-D as post-emergence] were included in the study. Results Early sowing took more days to reach various phenological phases, accumulated higher heat units, and recorded significantly higher thermal efficiencies, and yield than late sowing. Mechanical weeding took more time to complete different developmental stages, hence, accumulated higher heat units and recorded significantly higher thermal-use efficiencies and yield followed by application of bensulfuron methyl + pretilachlor as pre-emergence + 2,4-D as post-emergence. Conclusion Earlier sowing with 4 mechanical weedings or successive pre-emergence application of bensulfuron methyl + pretilachlor followed by post-emergence application of 2,4-D is recommended for better phenological development and yield of direct seeded rice.

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Abstract Background: The interference caused by volunteer soybean plants from grains lost before or during harvest can cause economic losses to bean producers due to the competition they cause, especially for succeeding crops. Objective: Therefore, the objective of this work was to determine the competitive ability and economic damage level (EDL) of bean cultivars in the presence of different densities of soybean volunteer plants. Methods: The experiments were installed in completely randomized design, and replicated for two consecutive years, 2020/21 and 2021/22. Treatments consisted of the carioca bean cultivars BRS Tangará, IAC 1850, and BRS Estilo and the black type IPR Uirapuru, IPR Urutau, and BRS Esteio, and 12 volunteer soybean densities established for each cultivar, ranging from 0 to a maximum of 66 plants m−2. Plant density, soil cover, leaf area, and shoot dry matter of volunteer soybean plants were determined 40 days after emergence. For bean, productivity, control cost, selling price, and control efficacy were determined. Results: Bean cultivars IPR Tangará, BRS Estilo, IPR Uirapuru and BRS Esteio showed greater competitive ability in the presence of soybean. The highest EDL values ranged from 1.00 to 2.89 plants m−2 for BRS Estilo, IPR Uirapuru, IPR Urutau and BRS Esteio cultivars when competing with soybean. Conclusions: Bean cultivars have different competitive abilities, and EDL is directly influenced by these different genetic traits.

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Abstract Background: Conventional method of rice cultivation has proven to be resource intensive, limiting its long term sustainability. On the contrary direct seeding offers a potential rice establishment method provided its increased susceptibility to weed infestation is taken care of. Objective: The principle aim of this study was to evaluate both pre- and post-emergence herbicides for effective weed suppression, while optimizing time window for herbicide application. Methods: A comprehensive two year study was conducted to assess the efficacy of new generation pre- and post-emergence herbicides including pendimethalin followed by 2,4-D, penoxsulam, pyrozosulfuron ethyl + pretilachlor, triafamone + ethoxysulfuron, ethoxysulfuron, fenoxyprop p-ethyl along with weed-free and weedy check treatments. Results: All herbicides substantially reduced weed biomass by 58–94% at 45 days after sowing. Pre- mix triafamone + ethoxysulfuron proved most effective against grasses and sedges, followed by penoxulam for sedges and pendimethalin followed by 2,4 -D for broadleaved weeds (BLW). Herbicide application significantly improved yield-related parameters compared to the weedy check. Application of pre-mix triafamone + ethoxysulfuron excelled, yielding 7.3 tons per hectare, a remarkable 383% increase over the weedy check. Key yield attributes such as panicles per square meter (349), grains per panicle (91), and 1,000-grain weight (25 g) were significantly elevated due to the application of triafamone + ethoxysulfuron (60 g a.i ha-1). Conclusion: Application of triafamone+ ethoxysulfuron an early post emergence herbicide witnessed significantly greater seed yield which was comparable to weed free situation besides, controlling diverse weed flora with higher weed control efficiency of 87 to 90%.

Resumo em Inglês:

Abstract: Background: Increased energy consumption in agriculture has led to growing environmental concerns and higher costs. The evolution of herbicide resistance in weeds may affect the herbicide application rate, energy consumption and greenhouse gas emissions. Objective: This study investigated the effect of herbicide resistance in weeds on energy consumption and greenhouse gas emissions in wheat fields of Golestan province, Iran. Methods: The data were collected from 351 wheat fields in Golestan province with respect to the proper distribution of sampling points. The farms were categorized into four classes according to the previous studies: 1) non-resistant fields; 2) fields with resistance to ACCase (acetyl-coenzyme A carboxylase) inhibitors; 3) fields with resistance to ALS (acetolactate synthase) inhibitors; and 4) fields with resistance to both ACCase and ALS inhibitors. Then, input and output energy, energy use efficiency, energy productivity, specific energy, net energy, percentage of direct, indirect, renewable and non-renewable energies, and greenhouse gas emission during wheat production were calculated. Results: Compared to non-resistant fields, evolution of resistance to herbicides led to increased energy consumption (5.7-8.2%) and yield loss (21.8-25.6%) and consequently, there was a decrease in net energy (25.6-31.3%), energy productivity (27.2-31.8%) and energy use efficiency (24.7-30.4%). Also, greenhouse gas emissions from the non-resistant fields were 7.4-10.0% lower than in the fields with herbicide-resistant weeds. Conclusions: Noting the negative effect of herbicide resistance in terms of energy consumption and greenhouse gas emission, efforts to properly manage herbicide-resistant weeds are essential both economically and ecologically.

Resumo em Inglês:

Abstract: Background: Weeds pose a significant challenge to Argentine crops, leading to herbicide resistance and environmental concerns. Objective: To identify key weed problems, assess management practices, and herbicide use. Methods: A web-based survey system, with closed questions, was distributed from March to August 2020 among 147 agricultural stakeholders related to soybean, corn, wheat, and sunflower crops in Argentina. Results: Notable troublesome weeds included Conyza bonariensis (L.) Cronq., Digitaria sanguinalis (L.) Scop., Eleusine indica (L.) Gaertn., Amaranthus hybridus L., and Sorghum halepense (L.) Pers. Herbicide usage was as follows: 86% used burndown fallow chemical control, 51% adhered to labeled application rates, 40% applied herbicides at the labeled growth stage, and 37% rotated modes of action. Non-chemical controls were also employed, with 67% favoring crop rotation and 36% focused on preventing weed seed production. Glyphosate was the dominant herbicide, employed by over 90% of respondents. For summer crops, frequently used herbicides included paraquat, 2,4-D (80% of respondents), atrazine (60% of respondents), sulfentrazone, flumioxazin, S-metolachlor (60% of respondents), and clethodim (65% of respondents). In winter cereals, 2,4-D, flurochloridone, flumioxazin, and pyroxasulfone were the top choices. Conclusions: This survey underscores the high reliance on chemical control in Argentina's major crops. The findings provide crucial insights for regional policy planning, emphasizing the importance of integrating diverse weed management tactics. It also highlights the need for proactive integrated management strategies at the field level to mitigate and prevent weed issues in Argentina, offering a valuable approach for analyzing weed problems in extensive crops worldwide.

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Abstract: Background: Chickpeas (Cicer arietinum) are an important type of pulse whose production is hindered by poor weed control. Objective: To assess lactofen selectivity levels and to uncover tolerance mechanisms in commercial genotypes. Methods: Four genotypes and weed species were grown under controlled-environment conditions and subjected to lactofen dose-response assays (11.2–2,880 g a.i. ha−1). Visual evaluations performed until 35 days after application, when biomass was quantified and selectivity indexes obtained using regression analysis. Following 14C-lactofen application, absorption and translocation were assessed until 168h after treatment (HAT), when chickpea plants were washed to remove the unabsorbed herbicide or subjected to autoradiography and tissue combustion. Lastly, 14C-lactofen was applied and metabolites extracted at 96 HAT, and their retention factors (Rf) determined by thin layer chromatography and radioscanner reading. Results: Tridax procumbens and Amaranthus spinosus were highly susceptible to lactofen. Chickpea genotypes tolerated lactofen at the highest labelled used rate in soybeans (180 g a.i. ha−1). Lactofen absorption was high (88.1%–94.6%) and translocation was limited (< 2.5%) across genotypes - a similar trend observed in susceptible species, and hence are not implicated in lactofen tolerance. One main metabolite was found in chickpea genotypes, accounting for 12.5%–19.4% of applied radioactivity; the chickpea genotype with the highest tolerance level (BRS Cicero) was the only one in which two metabolites were quantified. Altogether, these results suggest that lactofen tolerance in chickpeas could be conferred by enhanced herbicide metabolism. Conclusions: Lactofen could become an option for selective, post-emergence weed control in chickpeas.

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Abstract: Background: Knowing the relationships between the soil's physical-chemical properties and herbicide behavior in the soil allows establishing strategies for the efficient control of weeds with less environmental risk. Objective: It carried this study to investigate the role of physical-chemical properties of Brazilian soils in the sorption-desorption and mobility of the herbicide saflufenacil. Methods: We used nine soils from different regions of Brazil in the study of sorption-desorption and mobility of 14C-saflufenacil. The herbicide sorption-desorption estimate was performed using the batch equilibrium method and mobility using soil thin-layer chromatography. Principal component analysis (PCA) and clustering were performed to evaluate the impact of soil properties on the sorption-desorption behavior of saflufenacil. Results: The results indicated that saflufenacil was weakly sorbed in different types of tropical soils, and the sorption process is reversible, with its mobility varied from mobile (Rf = 0.70) to very mobile (Rf = 0.99) in the different soils and indicates that the herbicide has leaching potential in these types of soils. The sorption-desorption capacity and mobility of saflufenacil depend mainly on pH, CEC, clay, and OC content, and therefore it is vital to analyze them to predict the impacts of herbicide application on the environment. The PCA is an essential tool that helps to clarify how the effects of soil properties influence herbicide behavior. Conclusions: The OC content in Brazilian soils has a direct role in saflufenacil sorption and desorption. BR3 soil (soil with highest organic carbon; OC = 2,1%) exhibits greater sorption (Kd = 1,85 L kg−1), value 5.5 times greater than the BR1 (soil with lower sorption; with OC = 0,6%). Therefore, the application of saflufenacil to tropical soils, especially those with low levels of CO (< 1%), may result in a greater potential risk of contamination of surface and groundwater in neighbouring agricultural and non-agricultural areas, particularly those with intensive use and ineffectiveness of saflufenacil. Future investigations could focus on integrating modeling approaches that incorporate soil variability to predict saflufenacil behavior accurately in diverse soil types, aiding in decision-making for sustainable herbicide use.

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Abstract: Background: Atrazine, a pre-emergent weed control, can be mixed with paraforce or 2,4-D, however, the efficiency of the mixture nor the growth and yield performance of maize varieties under this treatment in the tropics is well establihsed. Objective: To determine efficacy of atrazine mixed with paraforce or 2,4-D as weed control method and yield performance of four yellow maize varieties (PVASYN8F2, BR9928-5R-Y, DSTRSYN2-Y and PVASYN2F2). Methods: In two years, four yellow maize varieties (PVASYN8F2, BR9928-5R-Y, DSTRSYN2-Y and PVASYN2F2.) and atrazine (1.5kg ha-1) mixed with paraforce, atrazine mixed with 2,4-D (1.5 L ha-1 in equal ratio; hand weeding and weedy (check) plots were arranged in split-plot using randomized complete block design with three replications. Fertilizers and pest control were done as practiced in the Teaching and Research Farm. Data were collected on maize vegetative and reproductive characters and analyzed using SAS ver 9.4 and Microsoft Excel. Results: Weed control efficiency (80%) and number of leaves per plant recorded for atrazine + paraforce plot were the highest. No significant grain yield difference was recorded among the varieties, but maximum grain loss was observed in no weeding field and the lowest was found in field treated atrazine + paraforce followed by Atrazine + 2,4-D. BR-9928-5R-Y among the varieties showed the least 44% grain loss while PVA SYN 2 F2 had the highest 53%. Conclusions: Atrazine + paraforce outperformed atrazine + 2,4-D as a pre-emergent weedicide and BR-9928-5R-Y variety produced the highest grain yield and minimum grain loss across all the treatments.

Resumo em Inglês:

Abstract: Background: The use of herbicides is a common practice to control weeds in oil palm plantation. However, high dependency on herbicides causes intense selection pressure, which could lead to the evolution of herbicide resistance in weed. Objective: To assess planters’ understanding of herbicide resistance management practices. Methods: Data were gathered via the application of questionnaires during the 2022 growing season to planters working with oil palm in Peninsular Malaysia and Indonesia. There were 101 respondents, covering about 14 states. Results: Planters (75 to 85% respondents) found herbicide rotation, cover crops, and pre-emergence herbicide application effective against herbicide-resistant weeds, but high herbicide costs hindered their selection of chemical solutions. Peninsular Malaysia planters (30 to 78% respondents) reported five major putative resistant weeds such as Eleusine indica (L.) Gaertn., Clidemia hirta (L.) D. Don., Melastoma malabathricum (L.), Ischaemum muticum (L.), and Asystasia gangetica (L.) T. Anderson. Indonesian planters (28 to 43% respondents) faced putative resistance in E. indica and C. hirta. Peninsular Malaysia's higher incidence of putative resistance was linked to insufficient knowledge of herbicide classification, less use of tank-mixed herbicides, and reduced herbicide rates, potentially fostering resistance evolution. Conclusions: The survey revealed that Indonesia planters possess a better understanding of herbicide resistance management as compared to Peninsular Malaysia planters. There is a need to increase awareness on sustainable use of herbicides through training and educational programs for planters in Peninsular Malaysia.

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Abstract: Background: Provisia rice and glyphosate-resistant soybean can control imidazolinone(IMI)-resistant weedy rice (WR-R) and reduce the soil seedbank. Objective: We evaluated different systems to reduce the WR-R soil seedbank under analysis when adopting soybean and Provisia rice (PV). Methods: From 2017 to 2022, a field experiment in randomized block design with four repetitions was performed. In 2017-2018, WR-R and Clearfield® rice (CL) were sown in the area. From 2018 to 2022, twelve systems [including CL, Provisia (PV), non-CL rice (NCL) and Soy] were used: S1) PV-PV-PV-PV, S2) CL-CL-CL-CL, S3) PV-CL-PV-CL, S4) PV-PV-Soy-CL, S5) PV-PV-CL-CL, S6) PV-Soy-PV-Soy, S7) Soy-PV-PV-Soy, S8) Soy-PV-PV-NCL, S9) PV-PV-PV-NCL, S10) Soy-PV-PV-CL, S11) Soy-Soy-PV-PV, and S12) PV-Soy-PV-CL. The WR-R management were CL – imazapyr + imazapic, PV – quizalofop-p-ethyl, NCL – no specific treatment, and Soy – glyphosate. WR-R plant density and soil seedbank were evaluated during the experiment. The systems were analyzed by year and each system over the years and the means were compared (LSD, p<0.05). Results: Over the years, no WR-R plant escapes (100% control) were observed in the systems using soybean or PV. However, even after three years of using alternative systems, the return of CL rice allowed seedbank replenishment. Thus, our results suggest that it takes more than four years to deplete the seedbank. The systems in which soybean (S6, S7, and S11) were used for two years were more efficient for soil seedbank reduction. Conclusions: Systems alternating soybean and Provisia rice for more than four years are a strategy to reduce imidazolinone-resistant weedy rice soil seedbanks.

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Abstract: Background: Mistletoes are commonly regarded as pests because they parasitize agricultural crops and have a detrimental impact on the quality of urban trees. Objective: To identify the species of mistletoe present in the Mata Alagoana microregion, Alagoas, Brazil, based on morphological and molecular characterization and to investigate host specificity. Methods: Collection expeditions were carried out in 16 municipalities within the Mata Alagoana microregion. Initially, the morphological characterization of the mistetloe was carried out based on dichotomous keys, comparison of exsiccates and confirmation with a specialist. Subsequently, the ITS region sequence of nine specimens was amplified using PCR and sequenced. Finally, species of ornamental plants, urban plants and crops of agricultural importance were recorded as hosts of mistetloes. Results: For the family Loranthaceae, four species of the genus Struthanthus were identified parasitizing different host plants, such as Syzygium cumini, Terminalia catappa and Artocarpus heterophyllus. Additionally, the species Passovia pyrifolia was found parasitizing Mangifera indica, Syzygium cumini and Manihot esculenta. Among the tree species, Mimosa caesalpiniaefolia showed greater susceptibility to infestation, indicating a preference of the parasite for this species. Psittacanthus dichroos was found to parasitize Terminalia catappa. For the family Viscaceae, the occurrence of three species of the genus Phoradendron was reported. P. quadrangulare parasitizing pomegranate (Punica granatum) and genipap (Genipa americana); P. dipterum was observed on P. perrottetii, reinforcing its epiparasitic habit; and P. perrottetii was found parasitizing white cupiúba (Tapirira guianensis), a very common host for this species. Conclusion: This report reinforces the wide distribution of mistletoe with emphasis on the municipalities of the Mata Alagoana microregion. Here, we report for the first time the occurrence of the species Struthanthus acuminatus, Phoradendron dipterum and Phoradendron perrottetii in the state of Alagoas.

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Abstract: Background: In recent years, the use of simultaneous pesticides in tank mixtures has greatly increased due to cost reduction, improved efficacy and minimizing environmental impact. Additionally, it has been shown that the detoxification of chemicals in plants can be enhanced by the inhibitory capability of some organophosphorus insecticides. Objective: This study aims to assess the joint action of binary mixtures of an insecticide and common herbicides using the additive dose model (ADM) as a reference. Methods: Four separate greenhouse experiments were conducted on Alhagi pseudalhagi (Bieb.) Desv. using seven doses of each of the following herbicides: malathion, 2,4-D, glyphosate, glufosinate-ammonium, and paraquat. Dose-response curves were analyzed with a three-parameter log-logistic model for pure and mixed ratios (100:0, 80:20, 60:40, 50:50, 40:60, 20:80, 0:100) to obtain ED50 values in R software, and ED80 and ED90 values in Excel®. Results: A potent synergism was found for mixtures of malathion with paraquat and/or glufosinate-ammonium on A. pseudalhagi, with sums of toxic units for the 50:50% effect mixture (ΣTU50:50) as low as 0.32 and 0.37, respectively. The mixture of malathion with glyphosate showed moderate synergism with ΣTU50:50 of 0.75. The binary mixture of malathion with 2,4-D followed ADM (additive effects), though it showed a slight synergism (λ-value > 1). Conclusion: This study highlights the importance of understanding synergistic pesticide interactions for more efficient weed management. By optimizing pesticide combinations, we can minimize resistance, reduce environmental impact, and achieve better control. Further research is needed to address limitations of the analysis tools and explore synergistic interactions further.

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Abstract Background: Sagittaria montevidensis Cham. & Schltdl. is a weed that forms dense infestations in wet-seeded rice. The herbicide florpyrauxifen-benzyl is widely used in rice cultivation; however, there have been reports of failed S. montevidensis control, and these cases are increasing. Objective: This study aimed to evaluate S. montevidensis for resistance the florpyrauxifen-benzyl and assess the sensitivity of this biotype to auxin-mimicking herbicides from other chemical groups. Methods: The experiments were conducted in greenhouse using a completely randomized design with four replicates. Dose-response tests were performed using two biotypes of S. montevidensis, resistant and sensitive. The experiments were performed over two generations, using increasing doses of the florpyrauxifen-benzyl. The experiment with other auxin mimics was conducted with the second-generation populations, using increasing doses of the herbicides 2,4-D, dicamba, and triclopyr. In both experiments, weed control was assessed at 7, 14, and 28 days after application (DAA), and the dry mass of the aerial part was determined at 28 DAA. Results: Resistance of S. montevidensis to florpyrauxifen-benzyl was confirmed, with a resistance factor >700 in the two evaluated generations. The biotype was sensitive to 2,4-D, dicamba, and triclopyr achieving greater than 80% control in all treatments, and cross-resistance to synthetic auxins was ruled out. Conclusions: Evolution of resistance to florpyrauxifen-benzyl by S. montevidensis seriously compromises paddy rice production, highlighting the urgent need for alternative approaches.

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Abstract: Background: Glyphosate-resistant Amaranthus hybridus biotypes have been observed in Rio Grande do Sul (RS) crops. Their impact on soybean yield is high due to rapid growth and competitiveness. Investigating the resistance mechanism guides management strategies. Objective: To confirm the evolution of glyphosate-resistant A. hybridus biotypes in southern RS, identifying the resistance mechanism and proposing alternative management strategies. Methods: Dose-response curve studies, investigation of EPSPS gene mutation, and analysis of integrated management practices were conducted to characterize glyphosate resistance in A. hybridus biotypes. Results: Three Amaranthus hybridus biotypes from Aceguá, Bagé, and Rosário do Sul (RS) exhibit triple mutations in the EPSPS gene, providing glyphosate resistance. Resistance levels are high (>10). Alternative mechanisms of action to glyphosate such as glufosinate-ammonium or 2,4-D choline salt (Enlist technology) in post-emergence and sulfentrazone + diuron (pre-emergence) control resistant plants without compromising soybean yield. Conclusions: Confirming Amaranthus hybridus resistance to glyphosate requires alternative control measures. Combining alternative mechanisms of action, such as those available in new technologies, is important and should be the main action in a control program. Important aspects of integrated management should be prioritized combined with herbicide use.

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Abstract Background drones for pesticide application have become more popular due to their practicality and reduction in cost. Accessing drone efficacy in herbicide application is needed. Objective This work aimed to determine the efficiency of drones in applying glyphosate and glufosinate to control ryegrass and oilseed radish compared to electrostatic and conventional ground herbicide applications. Methods The experiments were conducted in a factorial arrangement with five replications and repeated in time. Factor A consisted of spraying methods [drone, electrostatic ground spraying (electrostatic), and conventional ground spraying (conventional)], and factor B consisted of eight doses of glyphosate and glufosinate. A CO2 pressurized backpack was equipped with XR TeeJet® 11001VS spray nozzles for electrostatic and conventional applications, adjusted to a spray volume of 100 L ha-1. The drone, Pelicano® 2022 model (Skydrones), was equipped with the same spray nozzles but was regulated to a spray volume of 10 L ha-1. Results: The results demonstrated that glyphosate application via drones provided superior control of ryegrass and oilseed radish compared to terrestrial methods, whereas glufosinate’s effectiveness was comparable to that of ground-based applications. Conclusions drone application of glyphosate and glufosinate was efficient in controlling ryegrass and oilseed radish, being as good as ground spraying, even demonstrating that low spray volume does not significantly interfere with weed control in this study.

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Abstract Background The evolution of non-target site resistance (NTSR) to herbicides in weeds has made weed management extremely difficult. Weeds can develop NTSR to herbicides because of changes in one or more physiological processes. Objective This review aims to address the complexities of NTSR by investigating the factors influencing the evolution of NTSR in weeds. It explains mechanisms associated with NTSR and examines sustainable management strategies. Methods This review draws upon an extensive examination of existing literature on NTSR. It summarizes NTSR mechanisms in weeds and discusses strategies that delay the evolution of herbicide resistance. Results The analysis reveals that NTSR mechanisms threaten not only the efficacy of existing herbicides but also the utility of new herbicides. The study highlights that crop diversification, improved herbicide use patterns and understanding of weed biology, including fitness costs and gene flow, are crucial for developing sustainable weed management strategies. The study advocates a holistic approach, integrating diverse weed management practices and modern technologies, to effectively address the challenges posed by NTSR and ensure sustainable herbicide resistance management. Conclusions A holistic approach is urgently needed to manage NTSR. Understanding the complex interaction of genetic factors, inheritance patterns, effects of herbicide application patterns, and fitness costs is crucial for managing NTSR. This knowledge informs effective use of technology and conventional tools for effective weed control.

Resumo em Inglês:

Abstract Background: Several factors may affect herbicide fate in the soil, including soil moisture which can affect herbicide availability and degradation and mixture with other degradable herbicides. Objective: The objectives of this research were to evaluate the effects of soil moisture content and association with glyphosate on S-metolachlor persistence in lowland soil. Methods: Greenhouse experiments were conducted in 2011 and repeated in 2012 using a randomized complete block design in a factorial arrangement (3×3×5) with four replications. Factor A included three soil moisture contents (air-dried, water holding capacity, and saturated), and factor B included two herbicide combinations (S-metolachlor; S-metolachlor + glyphosate) plus an untreated check. Factor C included five intervals between application and sowing of the bioindicator species (rice): 150, 120, 90, 60, and 30 days before sowing. Herbicide injury, height in rice plants, and herbicide concentration in soil was evaluated. Results: S-metolachlor concentration and injury to rice were higher under dry soil conditions regardless of application timing. In contrast, rice injury was significantly lower in the soil saturated condition. The association with glyphosate did not affect S-metolachlor persistence in lowland soil. Conclusion: These results indicate that S-metolachlor exhibits shorter persistence under saturated soil conditions; and indicated that drought periods following S-metolachlor applications may increase carryover to sensitive crops planted in rotation.

Resumo em Inglês:

Abstract: Background: RNA interference (RNAi) is a natural post-transcriptional gene silencing (PTGS) system of eukaryotic cells and can be used as spray-induced gene silencing (SIGS) to target genes. Due to the complexity of plant cell structure and genome, using SIGS in plants has faced many barriers. Objective: We aimed to develop a delivery strategy and appropriate siRNA design to induce PTGS by SIGS. Methods: The rice Phytoene desaturase (OsPDS) gene was used as a model to test our SIGS. Three siRNAs (siPDS1, siPDS2, and siPDS3) targeting different regions of the OsPDS transcript were applied individually or mixed siPDS2+siPDS3 in solution with SilwetTM adjuvant. Treatments were applied using a micropipette in rice seedlings (V2-stage), with the addition of proper control treatments: untreated-check and adjuvant-check. Seedlings were accessed phenotypically, physiologically, and molecularly. Results: The most prominent phenotype was observed for siPDS1 and siPDS2+siPDS3. Reduction in plant growth, chlorophyll index and shoot dry mass were reduced after siPDS2+siPDS3 application, while increasing anthocyanin content. OsPDS was downregulated after siPDS1 application with no change in the non-treated upper leaf. Conclusions: Our siRNA design and delivery strategy efficiently delivered the siRNA inside the plant and promoted target PTGS and compatible phenotype. The system used in this experiment did not show systematicity in the plant, probably due to the fast oxidative stress that hindered the systematic effect. This is an advance on the SIGS and can be a valuable tool for PTGS to find new targets for RNAi.

Resumo em Inglês:

Abstract: Background: Echinochloa colona (junglerice), a troublesome weed in rice, is resistant to 15 herbicide active ingredients. High temperatures are linked to reduction of herbicide efficacy. Objective: Evaluate growth and seed production of junglerice, after five generations of recurrent selection with sublethal dose of rice herbicides under heat stress. Methods: Junglerice plants previously subjected to recurrent selection with herbicides and heat stress for three cycles were exposed to further iterative cycles of selection with heat stress (45 °C) and sublethal dose of florpyrauxifen-benzyl (FPB, 0.125x), imazethapyr (0.125x), quinclorac (0.25x), and glufosinate (0.25x). Plant injury was evaluated 1 and 3 weeks after treatment. Panicle number; plant height; and dry biomass of shoot, panicles, and seeds were recorded. Seed number plant-1 and reproductive effort were estimated. Results: The joint effect of heat stress and sublethal dose of herbicides reduced the sensitivity of junglerice to all herbicides tested. Plants treated with FPB and quinclorac produced more shoot biomass and seed number after five generations. Heat-stressed plants treated with FPB produced more seeds than non-stressed plants. Imazethapyr reduced seed production. Heat-stressed junglerice treated with glufosinate produced fewer seeds than non-stressed plants. Conclusions: The joint effect of heat stress and sublethal dose of herbicides reduced junglerice sensitivity to the four rice herbicides tested after five generations. Heat stress and sublethal dose of the relatively recent auxinic herbicide florpyrauxifen-benzyl reduced junglerice sensitivity and increased seed production.

Resumo em Inglês:

Abstract: In recent times, there has been an environmental pressure to reduce the amount of pesticides applied to crops and, consequently, the crop production costs. Therefore, investments have been made in technologies that could potentially reduce the usage of herbicides on weeds. Among such technologies, Machine Learning approaches are rising in number of applications and potential impact. Therefore, this article aims to identify the main machine learning algorithms used in integrated crop-livestock systems for weed management. Based on a systematic literature review, it was possible to determine where the selected studies were performed and which crop types were mostly used. The main research terms in this study were: "machine learning algorithms" + "weed management" + "integrated crop-livestock system". Although no results were found for the three terms altogether, the combinations involving "weed management" + "integrated crop-livestock system" and "machine learning algorithms" + "weed management" returned a significant number of studies which were subjected to a second layer of refinement by applying an eligibility criteria. The achieved results show that most of the studies were from the United States and from nations in Asia. Machine vision and deep learning were the most used machine learning models, representing 28% and 19% of all cases, respectively. These systems were applied to different practical solutions, the most prevalent being smart sprayers, which allow for a site-specific herbicide application.