Individual Herbicides Research Articles

Searching for consistent postemergence weed control in progressively inconsistent weather

Abstract Foliar applied postemergence herbicides are a critical component of corn and soybean weed management programs in North America. Rainfall and air temperature around the time of application may affect the efficacy of herbicides applied postemergence in corn or soybean production fields. However, previous research utilized a limited number of site-years and may not capture the range of rainfall and air temperatures that these herbicides are exposed to throughout North America. The objective of this research was to model the probability of achieving successful weed control (≥85%) with commonly applied postemergence herbicides across a broad range of environments. A large database of over 10,000 individual herbicide evaluation field trials conducted throughout North America was used in this study. The database was filtered to include only trials with a single postemergence application of fomesafen, glyphosate, mesotrione, or fomesafen + glyphosate. Waterhemp (Amaranthus tuburculatus (Moq.) J. D. Sauer), morningglory species (Ipomoea spp.), and giant foxtail (Setaria faberi Herrm.) were the weeds of focus. Separate random forest models were created for each weed species by herbicide combination. The probability of successful weed control deteriorated when the average air temperature within the first ten d after application was <19 or >25 C for most of the herbicide by weed species models. Additionally, dryer conditions prior to postemergence herbicide application reduced the probability of successful control for several of the herbicide by weed species models. As air temperatures increase and rainfall becomes more variable, weed control with many of the commonly used postemergence herbicides is likely to become less reliable.

Transcriptomic reprogramming of rice cultivars in response to herbicide, salt and their combined stresses

With the frequent fluctuations in global climate, plants are increasingly exposed to co-occurring abiotic stresses, which have adverse effects on plant growth and productivity. In order to understand the transcriptional responses of contrasting rice cultivars to combined stresses, we conducted transcriptome sequencing of rice seedlings grown under herbicide (2,4-Dichlorophenoxyacetic acid) and salinity (NaCl) treatments, both individually and in combination. The results revealed that the individual herbicide treatment alone led to the differential expression of genes related to herbicide response (such as Cytochrome P450), hormones regulation (including auxin, ethylene and abscisic acid), and glutathione metabolism, with unique patterns observed in each cultivar. Under saline stress, the resistant cultivar exhibited fewer unique stress-regulated differentially expressed genes (DEGs), while the sensitive cultivar showed increased expression of cation transporters compared to the resistant cultivar. The sensitive cultivar demonstrated greater susceptibility under the combined stress treatment, which was attributed to the malfunctioning of herbicide detoxification genes and the upregulation of key cation transporters (i.e. OsCNGCs, OsHKTs), resulting in unregulated Na+ accumulation and oxidative toxicity in plants. Conversely, the resistant cultivar exhibited enrichment and activation of salt responsive DEGs associated with stress response, osmotic stress, and redox balance. Functional analysis of the DEGs also indicated an interconnected relationship between oxidative metabolism and cation transporters, which are dynamically coordinated to maintain optimal cellular redox and ion balance. This coordination enables the initiation of proper signaling mechanisms to induce plant acclimation to individual or combined salinity and herbicide stresses.

Common use herbicides increase wetland greenhouse gas emissions

Wetlands play a disproportionate role in the global climate as major sources and sinks of greenhouse gases. Herbicides are the most heavily used agrochemicals and are frequently detected in aquatic ecosystems, with glyphosate and 2,4-Dichlorophenoxyacetic acid (2,4-D), representing the two most commonly used worldwide. In recent years, these herbicides are being used in mixtures to combat herbicide-tolerant noxious weeds. While it is well documented that herbicide use for agriculture is expected to increase, their indirect effects on wetland greenhouse gas dynamics are virtually unknown. To fill this knowledge gap, we conducted a factorial microcosm experiment using low, medium, and high concentrations of glyphosate or 2,4-D, individually and in combination to investigate their effects on wetland methane, carbon dioxide, and nitrous oxide fluxes. We predicted that mixed herbicide treatments would have a synergistic effect on greenhouse gases compared to individual herbicides. Our results showed that carbon dioxide flux rates and cumulative emissions significantly increased from both individual and mixed herbicide treatments, whereas methane and nitrous oxide dynamics were less affected. This study suggests that extensive use of glyphosate and 2,4-D may increase carbon dioxide emissions from wetlands, which could have implications for climate change.

Enhancing Wheat Yield and Economic Viability in Subtropical Rainfed Agriculture through Combined Herbicide Application

The management of weeds remains a critical aspect of agricultural production, particularly in rainfed subtropical regions where weed pressure can significantly impact crop yield and economic returns. This study aimed to evaluate the effects of combined herbicide applications on both the yield and economic viability of wheat (Triticum aestivum L.) in subtropical rainfed agricultural systems. Field trials were conducted over two consecutive growing seasons, employing a randomized complete block design with four treatments: (1) pre-emergence application of herbicide A, (2) pre-emergence application of herbicide B, (3) combined pre-emergence application of herbicides A and B, and (4) control (no herbicide application). The study assessed various parameters including weed density, wheat yield, and economic returns. Results indicated that the combined pre-emergence application of herbicides A and B significantly reduced weed density compared to individual herbicide applications and the control, consequently enhancing wheat yield. Furthermore, economic analysis revealed that the combined herbicide treatment resulted in the highest economic returns compared to individual herbicide applications and the control, indicating its economic viability in rainfed wheat cultivation in subtropical regions. These findings underscore the importance of integrated weed management strategies, particularly the judicious use of combined herbicide applications, for optimizing wheat yield and economic sustainability in subtropical rainfed agriculture.

Reduced irrigation impact on soil-applied herbicide dissipation and rotational crop response

Abstract Soil-applied herbicides are important for controlling weeds in many crops but risk damage to susceptible rotational crops if they persist. Field studies were conducted in Powell, WY, from 2015 through 2017 to evaluate the effect of reduced water availability on soil-applied herbicide dissipation. Eight soil-applied herbicides, applied to dry bean or corn, were exposed to three season-long irrigation treatments (100%, 85%, and 70% of estimated crop evapotranspiration [ETc]) by overhead sprinkler. Soil samples were collected to a depth of 10 cm from 0 to 140 d after application, and soil herbicide concentrations were quantified using gas or liquid chromatography and mass spectrometry. Herbicide concentrations were regressed over time to produce a soil half-life estimate for each herbicide and irrigation treatment. Reduced irrigation decreased dry bean yield by up to 77% and corn yield by up to 50%. After adjusting for precipitation, the lowest irrigation treatment received 78% and 76% as much water as the full irrigation treatment in 2015 and 2016, respectively. This significantly increased the soil half-life of imazethapyr but did not increase the soil half-life of atrazine, pyroxasulfone, saflufenacil, ethalfluralin, trifluralin, or pendimethalin. Reduced irrigation did not increase carryover injury to rotational crops from these herbicides 1 yr after application. Instead, carryover response was determined by the inherent persistence of individual herbicides. Imazethapyr (0.1 kg ai ha−1) injured rotational sugar beet, and isoxaflutole (0.1 kg ai ha−1) injured rotational dry bean. Pyroxasulfone (0.2 kg ai ha−1), atrazine (2.0 kg ai ha−1), saflufenacil (0.1 kg ai ha−1) + dimethenamid-P (0.6 kg ai ha−1), ethalfluralin (0.8 kg ai ha−1), trifluralin (0.6 kg ai ha−1), and pendimethalin (1.1 kg ai ha−1) did not injure rotational crops regardless of irrigation treatment. Drought stress sufficient to cause up to 77% crop yield loss did not increase soil-applied herbicide carryover.

Norflurazon and metribuzin as components of postemergence tank mixtures with HPPD-inhibiting herbicides for multiple-resistant waterhemp control

Field and greenhouse studies investigated the phytoene desaturase (PDS) and photosystem II (PSII)-inhibiting herbicides, norflurazon and metribuzin, as components of two- and three-way postemergence (POST) tank mixtures for controlling multiple herbicide-resistant (MHR) waterhemp (Amaranthus tuberculatus). Studies were conducted at two locations (Champaign County, Illinois, U.S.A (CHR) and McLean County, Illinois, U.S.A. (MCR)) during 2019 and 2020. One of three commercial HPPD-inhibiting herbicides (mesotrione, tembotrione or topramezone) was added to a tank mixture with norflurazon, a reduced rate of metribuzin, or both to determine if greater MHR waterhemp control with tank mixtures could be achieved compared to individual herbicides and assess the potential benefit of norflurazon. Field results indicated the addition of norflurazon to HPPD-inhibiting herbicides resulted in greater waterhemp control (14% increase on average) compared to individual herbicides applied alone. Additionally, metribuzin in combination with HPPD-inhibiting herbicides consistently increased control of MHR waterhemp populations compared to the herbicides applied alone. However, only the three-way tank mixture containing tembotrione at the MCR site reduced biomass relative to two-way treatments containing tembotrione, metribuzin or norflurazon. Greenhouse experiments characterized mixtures of norflurazon with metribuzin and the HPPD-inhibiting herbicides, mesotrione and topramezone. Waterhemp biomass was significantly reduced when metribuzin and HPPD inhibitors were combined in comparison to individual components. Two-way tank mixtures containing norflurazon with mesotrione or metribuzin also resulted in significant biomass reductions compared to herbicides applied alone in MHR waterhemp. However, lower control levels were noted in MHR waterhemp when norflurazon was mixed with either topramezone or topramezone plus metribuzin compared to topramezone alone. In summary, norflurazon and metribuzin can be effective tank mixture components with HPPD-inhibiting herbicides for MHR waterhemp control. However, more research on these tank mixtures is warranted to optimize weed control and crop selectivity, which includes investigating active ingredient ratios, application timings and droplet spectrum effects on coverage.

Efficacy of Sulfentrazone 39.6% and Pendimethalin as a Pre Emergence Application against Weed Spectrum of Soybean (Glycine max L. Merrill)

A field experiment was conducted during Kharif season of 2017 at the Research Farm, College of Agriculture, Jabalpur, Madhya Pradesh. The seven treatments comprising of four doses of sulfentrazone (180, 360, 540 and 720 g/ha), application of pendimethalin (750 g/ha) as pre emergence, hand weeding twice at 20 and 40 days after sowing (DAS) including weedy check, were laid out in randomized block design with 3 replications. Results revealed that, Echinochloa colona (28.24%) was the dominant weed species closely followed by Commelina communis (24.42%). However, other monocot weed like Cyperus rotundus (15.56%) and dicots like Phyllanthus niruri (19.34%) and Euphorbia hirta (12.44%) were also found associated with soybean in less numbers. Application of T4- sulfentrazone at 720 g/ha as pre emergence arrested the weed growth remarkably and proved superior to its lower dose (180 g/ha) and application of pendimethalin 750 g/ha. The poor crop-weed competition due to effective control of weeds under this treatment resulted in higher weed control efficiency. Pre-emergence application of T4- sulfentrazone at 720 g/ha recorded maximum grain yield and was at par with other individual herbicides. Similarly, higher net returns and benefit: cost ratio were recorded in T4- sulfentrazone at 720 g/ha fb T3- sulfentrazone at 540 g/ha. It may be inferred from the present investigation that these herbicidal treatments could be used effectively as an alternative for controlling weeds and obtaining optimum seed yield of soybean.

Chemical Site Preparation Mixtures, Application Timing, and Herbaceous Weed Control Impacts on Loblolly Pine Development Through Six Years

Abstract Chemical site preparation is a critical management practice for southern pine plantation establishment. Imazapyr and ester triclopyr are frequently used for chemical site preparation in the Lower Coastal Plain to control waxy leaf shrub species, yet limited information is available on optimal imazapyr and triclopyr tank mixes and individual herbicide application timing(s) to achieve maximum loblolly pine (Pinus taeda L.) growth. The objectives of this study were to determine the survival, growth, and stem defect response of 6-year-old loblolly pine to four chemical site preparation treatments plus an untreated control, three application timings, and first year herbaceous weed control (hwc) on a poorly drained flatwoods site. Treatments included two imazapyr and triclopyr rates applied as tank mixes, triclopyr and imazapyr alone, and an untreated control with hwc applied to half of each treatment plot. Results showed no treatment had superior survival or growth, whereas September-applied imazapyr and triclopyr tank mixes tended to result in improved growth. Triclopyr alone along with first year, banded hwc resulted in similar growth to imazapyr and triclopyr tank mixes. First-year hwc significantly enhanced survival and growth. Stem defects were more common in the chemical site preparation treatments than the control. Study Implications: Age-6-year results from this study indicate that loblolly pine (Pinus taeda L.) growth following application of chemical site preparation tank mixes containing imazapyr and triclopyr applied during September or October tended to be superior to July applications. Triclopyr applied alone with first growing season herbaceous weed control (hwc) may offer satisfactory near- and long-term loblolly pine growth as imazapyr and triclopyr tank mixtures on sites with similar competing vegetation. These findings may allow for less herbicide use on sites previously managed for pine production and show the importance of first year hwc for Coastal Plain flatwoods sites.

Analysis and management of herbicidal mixtures in a high-intensity agricultural landscape in Belgium.

Water bodies located in anthropogenically influenced environments, such as agricultural landscapes, may be exposed to different chemicals simultaneously or sequentially. Yet, current environmental risk assessments focus on single active substances for unintended mixtures. For 3.5 years, the present study monitored the mixture of herbicides, within an intensively managed agricultural catchment, accompanied by a stewardship program. Twelve herbicides and one metabolite were monitored on a daily to sub-daily basis, generating a unique, high temporal resolution data set, enabling an assessment of cumulative exposure in a worst-case scenario. Analyses focused on the number of events at which the herbicide mixture concentration exceeded the regulatory accepted concentration for algae and macrophytes, based on concentration addition, and the potential factors influencing the frequency of these events are considered. A low number of individual herbicides drove the toxicity and only two of these overlapped for the two organism groups, algae and macrophytes. The observed exceedance events coincided with seasonal influences, and low rainfall during the 2011 season correlated with a highly reduced number of these events. The major influence was found to be the implementation of the stewardship program, which directed farmers to use more advanced farming techniques, avoid spillages, and other point sources. The number of exceedance events was reduced by more than half for algae (9% of the daily mean samples in 2010 and 4% in 2013) and by approximately 10 times for macrophytes (36% in 2010 to 3% in 2013). This high-resolution monitoring data set illustrates how knowledge of the influencing factors can help reduce unintended exposure to chemicals and achieve real-world improvements. Overall, a single-substance assessment is protective of mixture effects. Where mixture effects do play a role, local measures to manage point sources are more effective than changes to the desk-based environmental risk assessments that focus on diffuse sources. Integr Environ Assess Manag 2023;19:1297-1306. © 2022 Cambridge Environmental Assessments RSK ADAS Ltd and Bayer AG. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The Survival Response of Earthworm (Eisenia fetida L.) to Individual and Binary Mixtures of Herbicides.

Frequent use of herbicides may impose a risk on non-target species. The objective was to test the combined toxic effect of binary herbicide mixtures—metribuzin:halosulfuron and metribuzin:flumioxazin—on non-target earthworms in two test systems: filter paper and a soil toxicity test system. The joint action experiments were independently run twice to substantiate the findings. The most potent individual herbicide was metribuzin, with a 50% lethal concentration (LC50) of 17.17 µg ai. cm−2 at 48 h in the filter paper test. The toxicity of the individual herbicides on the filter paper test was ranked as metribuzin>halosulfuron>flumioxazin. In the soil test, metribuzin and halosulfuron had high toxicity with an LC50 of 8.48 and 10.08 mg ai. kg−1, respectively, on day 14. Thus, the individual herbicide ranking did not change between the filter paper and artificial soil tests. The herbicide’s mixed effect in both test systems showed a consistent antagonistic effect relative to a Concentration Addition reference model. It indicates that the mixtures retracted the herbicide’s action in the earthworms.

Application of global sensitivity analysis in identification of herbicides cocktail effects at environment-related concentrations

<p indent="0mm">The use of herbicides in crop production continues to increase globally. By 2015, China had become one of the most important producers and consumers of herbicides in the world. Many herbicides are persistent organic pollutants and are used continuously for long periods of time, causing the high residual concentrations in the water surrounding farmland and negative effects on aquatic life. The concentrations of herbicides in the environmental water are variable and the types of herbicides are diverse. Herbicide mixtures in surface water may threaten aquatic life. However, in most areas of China, the hazard of herbicide mixtures associated with environmental exposure levels has not been assessed. This paper establishes a hazard identification assessment method for mixtures with environment-related concentrations. Firstly, the hazard of individual pollutant was assessed by hazard quotient (HQ), and the pollutants with high hazards (HQ≥1) to target organisms were further studied. Secondly, the global sensitivity analysis (GSA) based on Morris method was used to study combined effect, and identify the important or hidden drivers in chemical mixtures. In brief, the GSA experimental design consists of four steps: Input factors (target pollutants), Morris sampling, high-throughput screening, and the sensitivity analysis. Thirty-nine herbicides detected in the surface water of Tai Lake and Liao River were screened by HQ with <italic>Scenedesmus obliquus</italic> (<italic>S</italic>.<italic> obliquus</italic>) individually. The herbicides with high hazard were the input factors of GSA. Then, the Morris method was used to generate 150 samples of mixtures. The <italic>S</italic>.<italic> obliquus </italic>was exposed to 150 samples for <sc>24 h</sc> and subjected to high-throughput screening. Finally, the sensitivity analysis was used to identify the important or hidden drivers of the herbicide mixtures. The results showed that 14 herbicides had high hazards (HQ≥1) among 39 herbicides detected in Tai Lake and Liao River basin. Ametryn and diflufenican had higher hazards to algae. At the individual herbicide exposure of <sc>500 μg/L,</sc> most herbicides, except C5 and C10, significantly inhibited the growth of <italic>S</italic>.<italic> obliquus </italic>(<italic>P</italic>&lt;0.05). And the strongest growth inhibition effect caused by individual herbicide was about 40%. The results of 150 samples of mixtures with environment-related concentration showed that most of the mixtures had growth inhibition effects on <italic>S</italic>.<italic> obliquus</italic>. The total concentrations of the mixtures that consist of 14 herbicides are not greater than <sc>79 μg/L.</sc> And the strongest growth inhibition effect caused by mixture samples was over 50%. The toxicity of herbicide mixtures cannot be ignored. The growth inhibition effect of the mixtures that consist of 14 herbicides on <italic>S</italic>.<italic> obliquus</italic> was nonlinear, and there are strong interactions between herbicides. It is difficult to predict the toxic effects of the mixture system from the exposure concentration of individual herbicides. According to the <italic>μ*</italic> value, the most important factors in the combined pollution were terbutryne, bensulfuron methyl, atrazine, and ametryn. Bentazone had the lowest <italic>μ*</italic> and contributed little to the overall mixture system. And bensulfuron methyl was the hidden driver of the mixture system. The important drivers in the herbicide mixtures need to be focused, and their concentrations should be monitored regularly to control emissions and minimize the negative effect on aquatic life. Global sensitivity analysis based on Morris sampling can identify the important factors in cocktail effects of mixtures in limited samples, providing technical support for incorporating the actual toxic effects of mixtures into the risk assessment of pollutants.

Comparative Toxicity of Herbicide Active Ingredients, Safener Additives, and Commercial Formulations to the Nontarget Alga Raphidocelis Subcapitata.

Chloroacetanilide herbicides are used worldwide to control weeds that affect crops such as corn, soybeans, and cotton. These herbicides are frequently paired with a "safener," which prevents herbicidal damage to the crop without diminishing weed control. Formulated herbicide products that include safeners and other ingredients are infrequently assessed for toxicity. Our goal was to understand the potential toxicity of safeners and herbicide + safener formulations relative to the toxicity of associated active ingredients. We quantified the concentration of safeners in commercially available formulations and tested effects on nontarget algae, Raphidocelis subcapitata, when exposed to individual herbicide active ingredients, safeners, and commercial formulations. The median effective concentrations (EC50s) causing 50% reduction in population growth for the herbicide active ingredients S-metolachlor and acetochlor were 0.046 and 0.003 ppm, respectively. The safeners benoxacor, AD-67, furilazole, and dichlormid were all substantially less toxic than the herbicides and were not toxic at environmentally relevant concentrations. The commercial formulations Dual II Magnum®, Me-Too-Lachlor II®, Harness®, and Surpass EC® all resulted in EC50 values that fell within the 95% confidence interval of the associated active ingredient herbicide. Interestingly, a significant increase in cell size was observed when algae were exposed to all the formulations, herbicides (acetochlor and S-metolachlor), and safener (dichlormid). The safener furilazole caused a significant decrease in cell size, whereas benoxacor and AD-67 had no observed effect on algae cell size. Significant algae cell size effects all occurred at or above the EC50 concentrations for each chemical, suggesting that other morphological effects may be occurring. Importantly, safeners in commercial formulations appeared not to impact toxicity to R. subcapitata compared with the active ingredient alone.Environ Toxicol Chem 2022;41:1466-1476. © 2022 SETAC.

Conductive polymer layered semiconductor for degradation of triclopyr acid and 2,4-dichlorophenoxyacetic acid from aqueous stream using coalesce adsorption-photocatalysis technique

Polyaniline supported titanium dioxide nanoparticles (PTs) were fabricated using chemical oxidative aniline polymerization in the presence of titanium dioxide with ammonium peroxydisulfate as an oxidant. The synthesized PTs were thoroughly characterized for their morphological and functional features. PTs were employed for the photodegradation of acidic herbicides; 2,4-dichlorophenoxyacetic acid (2,4-D) and triclopyr acid (TCP). PT's surface modifications were imparted and their herbicide removal efficiencies were compared. The best operating conditions for adsorption/photocatalysis were 0.5 g/L photocatalyst, 10 mg/L concentration of individual herbicides resulted in 90.72% removal of TCP at pH 4 and 99.91% removal of 2,4-D at pH 5. Adsorption kinetics of herbicides, onto PT-1 showed the equilibrium attainment within 30 min and experimental data obeyed pseudo-second order model for TCP and 2,4-D removal which was governed by chemisorption. Analysis of TCP and 2,4-D adsorption indicated that the removal followed Sips model for TCP removal while Redlich-Peterson model explained the removal of 2,4-D by PT-1. Rate constants indicated that the amount of TiO2 in the PTs played an important role in removing the herbicides and PT-1 material excellent remarkable activity for three cycles of photodegradation. Thus, this work reports the polymerization of aniline onto TiO2 and their utility as photocatalyst for the expulsion of 2,4-D and TCP from water.

Hierarchical cluster analysis of herbicide modes of action reveals distinct classes of multiple resistance in weeds.

BACKGROUNDThe number of weed species resistant to multiple herbicide modes of action (MoAs) has increased over the last 30 years and may in the future render existing herbicide MoAs obsolete for many cropping systems. Yet few predictive tools exist to manage this risk. Using a worldwide dataset of weed species resistant to multiple herbicide MoAs, hierarchical clustering was used to classify MoAs into similar groups in relation to the suite of resistant weed species they have in common. Network analyses then were used to explore the relative importance of species prevalence and similarity in cluster patterns.RESULTSHierarchical clustering identified three similarly sized clusters of herbicide MoAs that were linked by the co‐occurrence of resistant weeds: Herbicide Resistance Action Committee (HRAC) groups 2, 4, 5 and 9; HRAC groups 12, 14 and 15; and HRAC groups 1, 3 and 22. Cluster membership was consistent with similarities in the physiological or biochemical target of the herbicide MoAs. Network analyses revealed that the number of weed species resistant to two different MoAs was related to the number of weeds known to be resistant to each individual herbicide MoA.CONCLUSIONSHierarchical cluster analysis provided new insights into the risk of weeds becoming resistant to more than one herbicide MoA. By clustering herbicide MoAs into three distinct groups, the potential exists for farmers to manage resistance by rotating herbicides between rather than within clusters, as far as crop, weed and environmental conditions allow.

The Joint Action of Some Broadleaf Herbicides on Potato (Solanum tuberosum L.) Weeds and Photosynthetic Performance of Potato

Herbicide mixtures are a modern weed management practice as they reduce herbicide application. This study aimes to evaluate the effect of metribuzin, halosulfuron and flumioxazin applied individually and as mixtures (metribuzin:halosulfuron and metribuzin:flumioxazin) on Chenopodium album, Amaranthus retroflexus, and potatoes on biomass and chlorophyll-a fluorescence in 21 experiments. The individual herbicide experimental design was a randomized completely block design with seven doses and three replications. The factorial experiments were performed on the basis of randomized completely block design in three replications for binary mixture experiments. Flumioxazin was very potent in controlling C. album, A. retroflexus, and injured potatoes with a 50% effective dose (ED50) of 1.21, 0.54, and 12.23 g ai·ha−1, respectively. Both mixtures of metribuzin:halosulfuron and metribuzin:flumioxazin generally showed an antagonistic effect on both weeds and potato in 12 independent experiments. Metribuzin, halosulfuron, and flumioxazin significantly decreased photosystem II activity by decreasing the maximum quantum efficiency (Fv/Fm). The metribuzin:halosulfuron mixtures almost followed the Additive Dose Model for Fv/Fm, whilst there was an antagonistic effect for the metribuzin:flumioxazin that was closely related to biomass. The results indicated that mixtures were generally antagonistic, and the endpoint choice is pivotal when assessing the joint action of mixtures.

Effectiveness of herbicide application on potatoes in the northern forest-steppe of the Novosibirsk Ob region

The work aims to study the effectiveness of herbicides application on potato varieties of different ripeness groups in the conditions northern forest-steppe of the Novosibirsk Ob region. The authors obtained experimental data on leached chernozem in Novosibirsk district, Novosibirsk region, in 2017-2019. In their studies, the authors used common elements of potato cultivation tech- nology. The general background for potatoes in autumn fertiliser was applied at a dose of P60K90. Nitrogen fertilisers were used at a rate of 60 kg/ha in spring under pre-sowing cultivation. Herbicides Gezagard, Lazurit, Zenkor, Boxer, and mixtures of individual herbicides were applied before and after sprouting when potato plants were up to 12-14 cm high. Herbicides significantly reduced the infestation of potato varieties Lubava (early) and Tuleevsky (medium-season). The authors showed that the use of herbicides accelerated the processes of growth and development of potato varieties of two groups of ripeness. There was a significant increase in leaf area, photosynthetic potential, and 23-28% plant productivity. On a background of herbicides increase of yield by 30-35% is observed. There was an increase in the marketability of tubers by 10%. Used herbicides provided good quality and preservation of potato production. The authors note that the double application of herbicides Zenkor and Lazurit offers high rates of weed reduction. Thus yield and quality of presentation have high indicators. In tubers of potatoes, the residual quantity of herbicides is not detected. Application of herbicides economically and energetically practical. The level of profitability exceeds control 1,4 times on a background of double spraying by herbicides Zenkor and Lazurit.

Herbicides Efficacy against Volunteer Oilseed Rape as Influenced by Spray Solution pH

The pH of the spray liquid is one of the factors influencing the efficacy of herbicides. Adjusting the appropriate parameters of the spraying liquid may reduce the consumption of pesticides, which is in line with the currently introduced legal standards and society’s requirements. In the greenhouse experiment, the influence of herbicides containing mesotrione, nicosulfuron, rimsulfuron, bromoxynil, and a mixture of nicosulfuron, rimsulfuron, and mesotrione on the efficacy of oilseed rape control was investigated. Oilseed rape (Brassica napus L. ssp. oleifera), apart from being an important crop, can become a nuisance weed in many fields as form of volunteer plants. Visual assessment, reduction of fresh weight, and chlorophyll fluorescence were performed. Individual herbicides influenced the tested parameters to a different extent. The pH of the spray liquid influenced the efficacy of individual plant protection products. The highest herbicidal efficacy in relation to the tested plants was observed in the case of combinations in which mesotrione was applied at a reduced and increased pH, nicosulfuron applied in an acidic and alkaline environment, rimsulfuron without pH modification, and all treatments in which bromoxynil was applied. The herbicides containing mesotrione and bromoxynil had the greatest impact on the photosystem II activity.

Dynamics of the Degradation of Acetyl-CoA Carboxylase Herbicides in Vegetables.

(1) Background: Aryloxyphenoxy-propionates and cyclohexanediones are herbicides most widely used in dicot crops worldwide. The main objective of the study was to determine the dynamics of herbicide residues in carrot, lettuce, cauliflower, and onion in order to suggest a low level of residues in harvested vegetables. (2) Methods: Small plot field trials were carried out in four vegetables in the Czech Republic. The samples of vegetables were collected continuously during the growing season. Multiresidue methods for the determination of herbicide residues by LC-MS/MS were used. Non-linear models of degradation of individual herbicides in vegetables were calculated using the exponential decay formula. Action GAP pre-harvest intervals for the 25% and 50% maximum residue limit (MRL) and 10 µg kg−1 limit (baby food) were established for all tested herbicides. (3) Results: The degradation dynamics of fluazifop in carrot, onion, and cauliflower was significantly slower compared to quizalofop and haloxyfop. The highest amount (2796 µg kg−1) of fluazifop residues was detected in cauliflower 11 days after application. No residue of propaquizafop and cycloxydim was detected in any vegetable samples. (4) Conclusions: Aryloxyphenoxy-propionate herbicide (except propaquizafop) could contaminate vegetables easily, especially vegetables with a short growing season. Vegetables treated with fluazifop are not suitable for baby food. Lettuce and cauliflower treated by quizalofop are not suitable for baby food, but in onion and carrot, quizalofop could be used. Propaquizafop and cycloxydim are prospective herbicides for non-residual (baby food) vegetable production.

Use of florpyrauxifen‐benzyl in non‐flooded rice production systems

AbstractThe lack of a flood on rice (Oryza sativa) levees and in furrow‐irrigated rice creates a favorable environment for terrestrial weeds like Palmer amaranth (Amaranthus palmeri S. Wats) to emerge and quickly overtake the crop for a longer portion of the year than in flooded rice culture. Florpyrauxifen‐benzyl is a new auxin herbicide labeled for use in rice that has activity on both grasses and broadleaf weeds, as well as certain sedges. Field experiments were conducted to determine the efficacy of florpyrauxifen‐benzyl in a non‐flooded environment. Experiments were conducted in 2017 and 2018 at the Lon Mann Cotton Research Station in Marianna, AR and the Pine Tree Research Station near Colt, AR to evaluate florpyrauxifen‐benzyl within a herbicide‐based weed control program in furrow‐irrigated rice. Programs evaluated included two preemergence herbicide combinations, four mid‐postemergence combinations, and a late‐postemergence application versus none. Another experiment was conducted at the Pine Tree Research Station in 2017 and 2018 to compare florpyrauxifen‐benzyl with 2,4‐D in different herbicide mixtures for weed control on rice levees. Treatments consisted of several commonly used rice herbicides applied alone and in a mixture with florpyrauxifen‐benzyl and with 2,4‐D. In the furrow‐irrigated rice experiment, programs containing florpyrauxifen‐benzyl in the mid‐postemergence application resulted in higher levels of late‐season Palmer amaranth control (96–98%) compared to the standard mid‐postemergence treatment (85%). Additionally, programs that included a late‐postemergence herbicide application controlled Palmer amaranth (98%) compared to programs where no late‐postemergence herbicide was applied (91%). In the levee experiment, mixtures where florpyrauxifen‐benzyl was used offered comparable control of Palmer amaranth to mixtures containing 2,4‐D. Mixtures where 2,4‐D or florpyrauxifen‐benzyl were used controlled Palmer amaranth better than the individual herbicide applied alone. Results from these experiments indicate florpyrauxifen‐benzyl will sufficiently control Palmer amaranth in a non‐flooded environment, providing a good alternative herbicide and viable weed control option in furrow‐irrigated rice and on rice levees.

Multi-mixture herbicides provide management strategies in the control of the aquatic weed Heteranthera reniformis

Heteranthera reniformis (mud plantain) is a weed of aquatic habit, which currently causes losses in the production of ornamental plants and irrigated crops, such as rice, and for which there are no herbicides registered in Brazil with proven control effectiveness. This study evaluated the control effectiveness of individual and multi-mixture herbicides (i.e., glyphosate, 2,4-D, triclopyr, paraquat, oxyfluorfen, sulfentrazone, carfentrazone, diuron and S-metolachor) on post-emergence of mud plantain. An organosilicone spreader adjuvant was also evaluated. Weed injury assessments were carried out over time, at 7, 14, 21, 42, and 60 days after application (DAA) of the herbicides. At the end of the study (60 DAA), the weed dry matter was measured. The progress of weed injury was modeled using a time-trend decomposition procedure based on the LOcally wEighted Scatterplot Smoothing (LOESS) method. Treatments with glyphosate application proved to be more effective in relation to mud plantain injury over time, with a slight emphasis on treatments associated with triclopyr. However, evaluating the dry matter, the treatment with glyphosate alone was more effective; besides, it showed short-range injury variance in the control of H. reniformis. The inclusion of organosilicone adjuvant to some treatments was not quite successful. Regardless of the herbicide used, higher levels of initial injury are a fair predictor of final control effectiveness (i.e., period after the herbicide effect). On the other hand, less initial injury corresponded directly to low control effectiveness. The results suggest that the herbicides, glyphosate, triclopyr, and carfentrazone, are suitable for mud-plantain control.