Synthetic Herbicides Research Articles

Weed Control in Organic Farming

Summary Over the past few years, both producers and consumers have become increasingly interested in organic farming because conventional agriculture relies so heavily on the use of synthetic pesticides, thus causing environmental pollution. Weeds, as inevitable "companions" of cultivated plants, represent a major, everlasting issue in plant production. As organic plant production is legally regulated, the control of undesirable plants such as weeds is further complicated. Using the relevant literature, the purpose of this study is to survey the existing weed control methods in organic crop production. In order to be certified, organic plants have to be grown in the farming system without the application of synthetic herbicides and other chemicals that are commonly used in conventional production. This means that crop growers have to apply non-chemical, alternative methods of weed suppression, i.e. weed control based on the combination of cropping practices, mechanical control, and the use of bioherbicides. There is a large number of plant extracts with bioherbicidal activity, the effect of which is mostly attributed to the biological phenomenon of allelopathy, rendering such weed control sustainable, inexpensive, and environmentally friendly. Although bioherbicides are successfully used in organic farming worldwide, there are no registered bioherbicides in Serbia to date (according to the data of the Ministry of Agriculture, Forestry and Water Management of the Republic of Serbia). Both organic producers and experts should raise awareness of the importance of successful weed control to the health of cultivated plants, soil, beneficial organisms, and the entire ecosystem, which requires further research attention.

Essential oils as natural root‐repellent herbicides for drip irrigation systems

AbstractThe increasing use of synthetic herbicides in agriculture creates severe ecological and environmental threats. Several essential oils (EOs) (Thymol, Carvacrol, Cinnamaldehyde, and Eugenol) were investigated as natural herbicides, and their potential use as a substitute for synthetic and toxic chemicals for preventing roots intrusion in subsurface drip irrigation systems. To overcome their high volatility and to increase their thermal stability during processing, multiphase hybrid blends based on polymer/nanoclays (NCs) were prepared, enabling control of the EOs migration rate from the final active film. Germination experiments on mash bean seeds in open and closed systems have been conducted to evaluate the EOs efficacy as germination inhibitors. The amount of EO remaining in the films, after processing and for varying timepoints, was determined by UV–Vis spectroscopy through extraction. From these two experiment's results, we identified Thymol as the most effective herbicide. The effects of polymers/Thymol affinity and organoclay polarity were investigated to achieve a slow‐release effect. Linear low‐density polyethylene/polyamide 6 system showed better efficiency compared to the linear low‐density polyethylene in retaining Thymol during processing due to the thermodynamic affinity of the polyamide 6 phase with Thymol. NCs have been found to be nuclear foci during the first thermal process to obtain smaller highly surface voids allowing better absorption of the Thymol during the second thermal processing. NC Cloisite 15A showed better dispersion in the polymer matrix and improved chemical affinity between the nanocomposite and the Thymol. As a result, Thymol's desorption was delayed and a controlled release was obtained. Eventually, it was concluded that Thymol could be a natural and environmentally friendly alternative to the synthetic herbicides and use as root‐repellent agent.

Agri-Food Waste as a Method for Weed Control and Soil Amendment in Crops

The continued and extensive use of synthetic herbicides to control weeds to maximize crop yield is no longer sustainable, as it results in negative impacts on the environment and human health. Innovative sustainable and resilient food production systems should preserve resources and environmental health by incorporating alternative natural herbicides, recycling waste, and favoring a circular economy. The present work assesses the value of different organic waste (Urtica dioica residues, Vicia faba pods, spent coffee grounds, and corn cobs) as bioherbicides and fertilizers in different seasons through pot and field two-year sequential experiments. Pot assays revealed that V. faba pods, spent coffee grounds, and corn cob waste showed the best inhibitory effect, which were subsequently evaluated in the Spring–Summer and Autumn crops. In the field, spent coffee grounds reduced the biomass of total naturally-emerged weeds and stimulated crop growth under scarce rainfall and warm days. However, its effect varied under different environmental conditions. Spent coffee grounds can partially control weeds in the field, which valorizes them as a bioherbicide and boosts sustainable agriculture.

Enantiomer-Selective Characterization of the Adsorption, Dissipation, and Phytotoxicity of the Plant Monoterpene Pulegone in Soils.

Plant monoterpenes have received attention for their ecological functions and as potential surrogates for synthetic herbicides, but very little is known about the processes that govern their behavior in the soil environment, and even less about the possible enantioselectivity in the functions and environmental behavior of chiral monoterpenes. We characterized the adsorption and dissipation of the two enantiomers of the chiral monoterpene pulegone in different soils, and their phytotoxicity to different plant species through Petri dish and soil bioassays. R- and S-pulegone displayed a low-to-moderate non-enantioselective adsorption on the soils that involved weak interaction mechanisms. Soil incubation experiments indicated that, once in the soil, R- and S-pulegone are expected to suffer rapid volatilization and scarcely enantioselective, biodegradation losses. In Petri dishes, the phytotoxicity of pulegone and its enantioselectivity to Lactuca sativa, Hordeum vulgare, and Eruca sativa was species-dependent. Lactuca sativa was the most sensitive species and showed higher susceptibility to S- than to R-pulegone. Biodegradation and volatilization losses greatly reduced the phytotoxic activity of S-pulegone applied to soil, but the addition of a highly-adsorptive organoclay stabilized the monoterpene and increased its phytotoxic effect. Stabilization by adsorption may represent an important mechanism by which the bioactivity of plant monoterpenes in soils can be increased.

Viability of Italian ryegrass (Lolium multiflorum) seeds under application of synthetic auxin herbicides

Italian ryegrass (Lolium multiflorum) is one of the main weeds in the wheat crop, and the application of synthetic auxin herbicides has the potential to reduce seed viability, therefore, restricting the input into the seed bank. The objective was to evaluate the effects of synthetic auxin herbicides applied at different growth stages on germination, emergence and initial growth of Italian ryegrass. The herbicides treatments were 2,4-D, 2,4-D+picloram and dicamba applied at four different growth stages of Italian ryegrass in field and seeds quality evaluated in laboratory and greenhouse studies. In both studies, the herbicides did not reduce Italian ryegrass seed germination or emergence regardless of application growth stages. Under laboratory conditions, the application of synthetic auxin herbicides increased vigor and germination speed by up to 64 and 47%, respectively, applied in growth stages. The greenhouse test evidenced an increase in vigor by the herbicides application, but only 2,4-D increased the emergence speed and plant dry matter when applied in early plant stage. The synthetic auxin herbicides do not alter germination or emergence. Progenies treated with herbicides had greater seed vigor.

Effect of the odour compound from Periploca sepium Bunge on the physiological and biochemical indices, photosynthesis and ultrastructure of the leaves of Humulus scandens (Lour.) Merr.

Natural odour compounds could be a potential alternative to synthetic herbicides. The odour compound of Periploca sepium Bunge, named 2-hydroxy-4-methoxy-benzaldehyde (HMB), is a herbicidal compound. However, its herbicidal mechanism is unclear. In this experiment, the physiological and biochemical indices, ultrastructure, and photosynthetic function of the leaves of Humulus scandens (Lour.) Merr. treated by HMB were assessed to elucidate the herbicidal mechanism. The results of physiological and biochemical indices are as follows: First, after 4 h of treatment with 2.5 and 5.0 mg/mL, the damage rates in the membrane permeation assay were 74.7% and 89.1%, respectively. Second, compared to the negative control group, multiple physiological and biochemical indices of the two treated groups were changed, including catalase content (−18.5 and −26.5 ng/mL), superoxide dismutase content (−27.4 and −56.6 ng/mL), peroxidase content (382.0 and 880.0 ng/mL), reactive oxygen species content (16.7 and 27.2 ng/mL), malondialdehyde content (8.9 and 25.2 nmol/g), and water potential values (0.2 and 0.3 MPa), except for the photosynthetic pigment contents (chlorophyll a, b, and carotene). Furthermore, the results of transmission electron microscopy showed that the organelles in the mesophyll tissue cells disappeared and severe plasmolysis led to cell atrophy after 4 h of treatment. There were fewer starch granules after 24 h of treatment, but there was no obvious abnormality in the upper and lower epidermal cells. The results of photosynthetic function showed that in the light response, the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and stomatal limitation value of the tested leaves were lower than those of the negative control group by 26.6 μmol·m−2·s−1, 7.7 mmol·m−2·s−1, 0.9 mol·m−2·s−1, and 0.2, respectively. However, the intercellular CO2 concentration (Ci) increased and was higher than the air CO2 concentration. In the CO2 response, the Pn, Tr and Gs of the tested leaves first increased and then decreased, but the Ci value continuously increased and finally reached 1727.5 μmol·mol−1. It is obvious that HMB may have inhibited the effect on the photosynthetic system of the tested leaves. Overall, HMB killed the weeds by destroying the structure and multiple physiological functions of the tested leaves.

Effect of simulated synthetic auxin herbicide sprayer contamination in sweetpotato propagation beds

AbstractField studies were conducted to determine the effects of synthetic auxin herbicides at simulated exposure rates applied to ‘Covington’ sweetpotato propagation beds on the quality of nonrooted stem cuttings (slips). Treatments included diglycolamine salt of dicamba, 2,4-D choline plus nonionic surfactant (NIS), and 2,4-D choline plus glyphosate at 1/10, 1/33, or 1/66 of a 1X application rate (560 g ae ha−1 dicamba, 1,065 g ae ha−1 2,4-D choline, 1,130 g ae ha−1 glyphosate) applied at 2 or 4 wk after first slip harvest (WASH). Injury to sweetpotato 2 wk after treatment was greatest when herbicides were applied 2 WASH (21%) compared to 4 WASH (16%). More slip injury was caused by 2,4-D choline than by dicamba, and the addition of glyphosate did not increase injury over 2,4-D choline alone. Two weeks after the second application, sweetpotato slips were cut 2 cm above the soil surface and transplanted into production fields. In 2019, sweetpotato ground coverage 8 wk after transplanting was reduced 37% and 26% by the 1/10X rates of dicamba and 2,4-D choline plus NIS, respectively. Though dicamba caused less injury to propagation beds than 2,4-D choline with or without glyphosate, after transplanting, slips treated with 1/10X dicamba did not recover as quickly as those treated with 2,4-D choline. In 2020, sweetpotato ground coverage was 90% or greater for all treatments. Dicamba applied 2 WASH decreased marketable sweetpotato storage root yield by 59% compared to the nontreated check, whereas treatments including 2,4-D choline reduced marketable yield 22% to 29%. All herbicides applied at 4 WASH reduced marketable yield 31% to 36%. The addition of glyphosate to 2,4-D choline did not increase sweetpotato yield. Results indicate that caution should be taken when deciding whether to transplant sweetpotato slips that are suspected to have been exposed to dicamba or 2,4-D choline.

Current Status of Herbicide Resistance in the Iberian Peninsula: Future Trends and Challenges

The evolution of herbicide resistance in weeds has emerged as one of the most serious threats to sustainable food production systems, which necessitates the evaluation of herbicides to determine their efficacy. The first herbicide resistance case in the Iberian Peninsula was reported about 50 years ago, wherein Panicum dichotomiflorum was found to be resistant (R) to atrazine in Spanish maize fields. Since then, herbicide resistance has evolved in 33 weed species, representing a total of 77 single-herbicide-resistance cases in this geographic area: 66 in Spain and 11 in Portugal. Changes in agricultural practices, namely the adoption of non-tillage systems and the increased use of herbicides, led to the selection of weed biotypes resistant to a wide range of herbicides. Nowadays the most important crops in Spain and Portugal (maize, winter cereals, rice, citrus, fruits, and olive orchards) are affected, with biotypes resistant to several mechanisms of action (MoAs), namely: ALS inhibitors (20 species), ACCase inhibitors (8 species), PS II inhibitors (18 species), and synthetic auxin herbicides (3 species). More recently, the fast increase in cases of resistance to the EPSPS-inhibiting herbicide glyphosate has been remarkable, with 11 species already having evolved resistance in the last 10 years in the Iberian Peninsula. The diversity of resistance mechanisms, both target-site and non-target-site, are responsible for the resistance to different MoAs, involving point mutations in the target site and enhanced rates of herbicide detoxification, respectively. More serious are the 13 cases reported with multiple-herbicide resistance, with three cases of resistance to three–four MoAs, and one case of resistance to five MoAs. Future research perspectives should further study the relationship between management strategies and the occurrence of TSR and NTSR resistance, to improve their design, develop monitoring and diagnostic tools for herbicide resistance, and deepen the study of NTSR resistance.

Phytotoxic Effects of Acetic Acid and d-limonene on Four Aquatic Plants

Herbicides that are labeled for aquatic use are often the foundation of aquatic vegetation management programs in the United States because many of these products, which are registered by the U.S. Environmental Protection Agency, are effective, selective, and relatively inexpensive. Resource managers are interested in reducing the use of synthetic herbicides and are considering alternative methods for aquatic weed control. We evaluated the effects of acetic acid and d-limonene on growth of the invasive small floating species feathered mosquitofern (Azolla pinnata) and common salvinia (Salvinia minima), as well as on the native emergent wetland plants cattail (Typha latifolia) and gulf coast spikerush (Eleocharis cellulosa). Acetic acid and d-limonene (alone and in combination) were applied once as foliar treatments to healthy plants, which were grown for 8 weeks after treatment to allow for development of phytotoxicity symptoms. All experiments also included diquat dibromide at three concentrations as “industry-standard” treatments for comparison. A 0.22% concentration of diquat dibromide eliminated all vegetation of all species. Most single-product treatments provided good control of invasive feathered mosquitofern with acceptable levels of damage to native gulf coast spikerush, but only 15% and 20% d-limonene treatments were effective on invasive common salvinia and selective for native cattail. Some combinations of acetic acid and d-limonene provided acceptable control of both floating weeds and selectivity for gulf coast spikerush, but all mixes caused unacceptable levels of damage to cattail. Treating these small floating weeds with acetic acid and d-limonene instead of diquat dibromide would increase material costs by 15- to 27-fold. Although these natural products may be useful in some areas where synthetic herbicides are discouraged, they are unlikely to be affordable options for most resource managers.

Allelopathic effect of weed extracts on vegetable seeds

Protection of cultivated agricultural crops from weeds is one of the most important tasks of soil management as a science. Weed control is mainly dependent on the use of synthetic herbicides. The treatment of crops with herbicides inhibits and destroys not only weeds, but inhibits the growth and development of cultivated plants, and also affects the safety of crop production. Weed growth can be suppressed by the plants’ allelopathic effects. As a form of plant interaction in plant cenoses, allelopathy is a cycle of physiologically active substances (colins), which regulate internal and external relationships, renewal, development and change of vegetation cover in biogeocenosis. In agrophytocenosis, both cultivated and weed plants can be donors of physiologically active substances. The article presents the results of studies on the allelopathic effect of weeds on the germination energy and laboratory germination of beet and carrot seeds. It was found that extracts from Capsella bursa-pastoris Medic and Sonchus arvensis L. had the maximum inhibitory effect on the germination of carrot seeds at a concentration of 10%. An average allelopathic activity on the beet seeds’ germination energy was produced by extracts from Sonchus arvensis L. at concentrations of 5% and 10%. Seed germination ranged from 50.5 to 65.0% depending on crop varieties.

Expression of a Cytochrome P450 Gene from Bermuda Grass Cynodon dactylon in Soybean Confers Tolerance to Multiple Herbicides.

Bermuda grass (Cynodon dactylon) is notoriously difficult to control with some commonly used herbicides. We cloned a cytochrome P450 gene from Bermuda grass, named P450-N-Z1, which was found to confer tolerance to multiple herbicides in transgenic Arabidopsis. These herbicides include: (1) acetolactate synthase (ALS) inhibitor herbicides nicosulfuron and penoxsulam; (2) p-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide mesotrione; (3) synthetic auxin herbicide dicamba; (4) photosynthesis inhibitor bentazon. We further generated transgenic soybean plants expressing P450-N-Z1, and found that these transgenic soybean plants gained robust tolerance to nicosulfuron, flazasulfuron, and 2,4-dichlorophenoxyacetic acid (2,4-D) in greenhouse assays. A field trial demonstrated that transgenic soybean is tolerant to flazasulfuron and 2,4-D at 4-fold and 2-fold the recommended rates, respectively. Furthermore, we also demonstrated that flazasulfuron and dicamba are much more rapidly degraded in vivo in the transgenic soybean than in non-transgenic soybean. Therefore, P450-N-Z1 may be utilized for engineering transgenic crops for herbicide tolerance.

Sensitivity to sublethal rates of dicamba for selected mid-Atlantic vegetable crops

AbstractDicamba is a synthetic auxin herbicide that may be applied over the top of transgenic dicamba-tolerant crops. The increasing prevalence of herbicide-resistant weeds has resulted in increased reliance on dicamba-based herbicides in soybean production systems. Because of the high volatility of dicamba it is prone to off-target movement, and therefore concern exists regarding its drift onto nearby specialty crops. The present study evaluates 12 mid-Atlantic vegetable crops species for sensitivity to sublethal rates of dicamba. Soybean, snap bean, lima bean, tomato, eggplant, bell pepper, cucumber, summer squash, watermelon, pumpkin, sweet basil, lettuce, and kale were grown in a greenhouse and exposed to dicamba at 0, 0.056, 0.11, 0.28, 0.56, 1.12, 2.24 g ae ha−1, which is, respectively, 0, 1/10,000, 1/5,000, 1/2,000, 1/1,000, 1/500, and 1/250 of the maximum recommended label rate for soybean application (560 g ae ha−1). Vegetable crop injury was evaluated 4 wk after treatment using visual rating methods and leaf deformation index measurements. Overall, snap bean was the most sensitive crop, with dicamba rates as low as 0.11 g ae ha−1 resulting in significantly higher leaf deformation levels compared with the nontreated control. Other Fabaceae and Solanaceae species also demonstrated high sensitivity to sublethal rates of dicamba with rates ranging 0.28 to 0.56 g ae ha−1 causing higher leaf deformation compared with the nontreated control. While cucumber, pumpkin, and summer squash were no or moderately sensitive to dicamba, watermelon showed greater sensitivity with unique symptoms at rates as low as 0.056 g ae ha−1 based on visual evaluation. Within the range of tested dicamba rates, sweet basil, lettuce, and kale demonstrated tolerance to dicamba with no injury observed at the maximum rate of 2.24 g ae ha−1.

Opportunities for Microbiome Suppression of Weeds Using Regenerative Agricultural Technologies

The goal of regenerative agriculture is to utilize technologies that build healthy soils and improve the environment. Microbial technologies could play a significant role in reducing reliance on synthetic herbicides for weed control. In the United States, the expenditure on herbicides exceeds $5 billion annually and accounts for 58% of the total pesticide use nationally. This overreliance on chemical weed control has exacerbated herbicide resistance in a multitude of weed species, leading to aggressive cultivation practices that contribute to soil erosion and depletion. The proliferation of microbiome research in agriculture has increased our understanding of the complex interactions between plant species and their microbiota. Microbial technologies offer novel weed management strategies that could reduce the need for herbicides. Some of these strategies could also help rebuild soil and improve environmental quality. Specifically, we propose three emerging areas in microbiome science that can enhance weed management: (1) identifying soil microorganisms that inhibit weed growth; (2) discovering microbial natural products that suppress weeds; and (3) developing field management approaches that promote weed suppression by enhancing soil microbiome function.

Antioxidant Activities and Allelopathic Potential of Chonemorpha splendens Chun et Tsiang Stem Methanol Extract.

Finding agriculturally active compounds from nature or finding active lead compounds from natural products, artificial synthesis and structural modification are the main ways to create new agrochemical. In order to explore the agricultural activities of Chonemorpha splendens Chun et Tsiang (C. splendens), an important medicinal plant, the antioxidant activities and allelopathic potential were investigated. C. splendens was extracted with methanol, then, C. splendens methanol extract (CSME) were extracted with petroleum ether, chloroform, ethyl acetate and butanol. Reducing activity, lipid peroxidation, and the scavenging abilities for DPPH⋅, O2 -. , HO⋅, and H2 O2 were also measured and allelopathic potentials were evaluated by bioassay method. GC/MS analysis revealed that esters were the main component (66.34 %) of CSME, the total CSME flavonoid content was 313 mg g-1 (rutin equivalent). The chloroform phase of CSME was identified as stigmasterol by NMR for the first time. The DPPH⋅ scavenging rate of CSME was 87 %, with an IC50 value of 0.12±0.02 mg mL-1 , which was significantly difference from the positive control, Trolox. Chloroform fraction showed the strongest inhibitory effect against Mimosa pudica (MP) seed germination at 1.0 mg mL-1 (100 % inhibition), which was better than that of the chemical herbicide paraquat. In the seed growth experiment, systematic EC50 and the principal component analysis (PCA) were used to assess the allelopathic potential of extracts. The systematic EC50 values of Crotalaria pallida Ait. (CP), Bidens pilosa L. (BP) were significantly greater than MP. MP, Oryza sativa L. (OS) and Lactuca satiua L., (LS) inhibited all parameters. Our results would provide an idea for controlling weeds through allelopathy from C. splendens to reduce dependency on synthetic herbicides.

Determination of Dissolved Pesticide Leachates in the West Africa’s Largest Natural Lake

Lake Bosomtwe in the Ashanti Region of Ghana is one of the largest naturally occurring lake in West Africa. The lake is surrounded by about 36 farming and fishing communities that use synthetic pesticides and herbicide in the cultivation of crops. These chemicals are likely to leak into the tributaries, contaminate the lake, and threaten the life of the aquatic animals. For this reason, a study of the levels of the active components of the pesticides in the lake were measured to monitor the water quality. A Gas Chromatographic equipped with Electron Capture Detector (GC-ECD) was employed in the measurements and levels of organochlorine, organophosphorus and pyrethoids. The GC-ECD analysis revealed that, the mean concentrations of organochlorines in the water sample were, Beta – HCH (0.03µg/L), Gamma – HCH (0.015 µg/L), Delta – HCH (0.012 µg/L), Endrin (0.014 µg/L), Beta-endosulfan (0.01 µg/L), Endosulfan (0.028 µg/L), and p, p’- DDT (0.012 µg/L). Heptachlor, Alpha-endosulfan, p,p’- DDE and Lambda-cyhal had concentrations less than 0.01 µg/L. Chloropyrifos was the only organophosphate detected with a mean concentration of 0.013 µg/L. The mean concentrations of the pyrethoids present were, permethrin 0.024 µg/L, cyfluthrin 0.016 µg/L and deltamethrin 0.017µg/L. A comparison of the measured concentrations with the WHO pesticides limit in water displayed lower levels and compliance to the standards. Detection of these pesticides residues indicates that, regulating farming activities along the boundaries of the lake will reduce the leakages with corresponding positive effect on the aquatic life.

Seasonal Changes in the Plant Growth-Inhibitory Effects of Rosemary Leaves on Lettuce Seedlings.

Plant biodiversity has been studied to explore allelopathic species for the sustainable management of weeds to reduce the reliance on synthetic herbicides. Rosemary (Rosmarinus officinalis L., syn Salvia rosmarinus Spenn.), was found to have plant growth-inhibitory effects, and carnosic acid was reported as an allelochemical in the plant. In this study, the effects of seasonal variation (2011–2012) on the carnosic acid concentration and phytotoxicity of rosemary leaves from two locations in Tunisia (Fahs and Matmata) were investigated. The carnosic acid concentration in rosemary leaves was determined by HPLC, and lettuce (Lactuca sativa L.) was used as the receptor plant in the phytotoxicity bioassay. The highest carnosic acid concentration was found in rosemary samples collected in June 2011, which also had the highest inhibitory activity. Furthermore, a significant inverse correlation (r = −0.529; p < 0.01) was found between the inhibitory activity on lettuce hypocotyl and the carnosic acid concentration in rosemary leaves. Both temperature and elevation had a significant positive correlation with carnosic acid concentration, while rainfall showed a negative correlation. The results showed that the inhibitory effects of rosemary leaf samples collected in summer was highest due to their high carnosic acid concentration. The phytotoxicity of rosemary needs to be studied over time to determine if it varies by season under field conditions.

An in-frame deletion mutation in the degron tail of auxin coreceptor IAA2 confers resistance to the herbicide 2,4-D in Sisymbrium orientale.

The natural auxin indole-3-acetic acid (IAA) is a key regulator of many aspects of plant growth and development. Synthetic auxin herbicides such as 2,4-D mimic the effects of IAA by inducing strong auxinic-signaling responses in plants. To determine the mechanism of 2,4-D resistance in a Sisymbrium orientale (Indian hedge mustard) weed population, we performed a transcriptome analysis of 2,4-D-resistant (R) and -susceptible (S) genotypes that revealed an in-frame 27-nucleotide deletion removing nine amino acids in the degron tail (DT) of the auxin coreceptor Aux/IAA2 (SoIAA2). The deletion allele cosegregated with 2,4-D resistance in recombinant inbred lines. Further, this deletion was also detected in several 2,4-D-resistant field populations of this species. Arabidopsis transgenic lines expressing the SoIAA2 mutant allele were resistant to 2,4-D and dicamba. The IAA2-DT deletion reduced binding to TIR1 invitro with both natural and synthetic auxins, causing reduced association and increased dissociation rates. This mechanism of synthetic auxin herbicide resistance assigns an in planta function to the DT region of this Aux/IAA coreceptor for its role in synthetic auxin binding kinetics and reveals a potential biotechnological approach to produce synthetic auxin-resistant crops using gene-editing.

Managing invasive plants through a nature-based approach in complex landscapes

Invasive plants are establishing in many protected areas where use of synthetic herbicides is prohibited. We introduce a nature-based approach (NbA) as an alternative to controlling invasives. The integration of NbA into ecosystem conservation provides potential to suppress invasive plants, improve soil cover, increase the diversity of native plants, and ultimately ensure ecosystem sustainability.

Controlling Woody Weed Chinese Elm (Celtis sinensis Pers.) with Stem-Implanted Herbicide Capsules.

Chinese elm [Celtis sinensis Pers.] is an emerging environmental weed naturalised throughout the coastal and riparian (creek-banks, river margins, and streams) regions of eastern Australia. Throughout this introduced range, its management is limited to the application of synthetic herbicides and mechanical clearing operations (terrain and soil type permitting). The current mechanisms of chemical control (basal bark spraying, stem-injection, and cut-stump applications) often result in collateral damage to non-target native species (such as Eucalyptus spp. and Casuarina cunninghamiana Miq.) through herbicidal drift, runoff or leaching into adjacent habitats. This has raised concerns regarding the suitability of synthetic herbicides in ecologically sensitive (e.g., riparian zones, rainforest margins, and woodlands) or low-value habitats, thereby promoting significant developments in the fields of integrated weed management. This study investigated the effectiveness of a novel stem-implantation system for controlling woody weed species in the context of a conserved habitat. A replicated trial (n = 315) was established among a naturally occurring population of C. sinensis. This trial involved the mapping, measurement, and treatment of this invasive species with five encapsulated synthetic herbicides, as well as an untreated control and benchmark treatment (diesel + AccessTM). A significant effect (p < 0.05) on plant vigour and functional canopy was discerned for each assessment period following trial establishment. The highest incidence of mortality was observed among the individuals treated with glyphosate (245 mg/capsule), aminopyralid and metsulfuron-methyl (58.1 and 37.5 mg/capsule) and picloram (10 mg/capsule), achieving a similar response to the basal bark application of diesel and AccessTM (240 g/L triclopyr, 120 g/L picloram, and 389 g/L liquid hydrocarbon). This was also evidenced by a rapid reduction in functional canopy (i.e., no or little living leaf tissue) from three weeks after treatment. Unlike their industry counterparts, these encapsulated herbicides are immediately sealed into the vascular system of the target species by a plug. This significantly minimises the possibility of environmental or operator exposure to synthetic compounds by providing a targeted, readily calibrated herbicide application.

The combination of organic and inorganic fertilizers influence the weed growth, productivity and soil fertility of monsoon rice.

Synthetic fertilizer and herbicides encompass the largest share in nutrient and weed management on food grain crops that create serious environmental issues. Integrated nutrient and non-chemical weed management approaches may help to reduce the chemical load in the environment, maintaining higher weed control efficiency and yield. A field experiment was conducted for two consecutive monsoon seasons during 2015 and 2016 in farm fields to develop a profitable and sustainable rice production system through integrated nutrient and weed management practices. A varied combination of nutrients either alone or integrated with chemical and non-chemical weed management were tested on transplanted rice in a factorial randomized block design with three replications. The results showed that the integration of concentrated organic manures with chemical fertilizer effectively inhibited weed growth and nutrient removal. Integration of nutrient and weed management practices significantly enhanced 9% biomass growth, 10% yield of the rice crop along with 3-7% higher nutrient uptake. Brassicaceous seed meal (BSM) and neem cake also had some influence on weed suppression and economic return. Thus, the integrated nutrient and weed management practices in rice cultivation might be an effective way to achieve economic sustainability and efficient rice cultivation in eastern India. Shortages of farmyard manure and vermicompost could be supplemented by BSM and neem cake in the integrated module.