Synthetic Herbicides Research Articles

Cytochrome P450 metabolism-based herbicide resistance to imazamox and 2,4-D in Papaver rhoeas

Papaver rhoeas biotypes displaying multiple herbicide resistance to ALS inhibitors and synthetic auxin herbicides (SAH) are spreading across Europe. In Spain, enhanced metabolism to imazamox was confirmed in one population, while cytochrome-P450 (P450) based metabolism to 2,4-D in another two. The objectives of this research were to further confirm the presence of P450 mediated enhanced metabolism and, if so, to confirm whether a putative common P450 is responsible of metabolizing both 2,4-D and imazamox. Metabolism studies were undertaken in five P. rhoeas populations with contrasted HR profiles (herbicide susceptible, only HR to ALS inhibitors, only HR to SAH, or multiple HR to both), and moreover, three different P450 inhibitors were used. The presence of enhanced metabolism to these SoA was confirmed in three more HR P. rhoeas populations. This study provides the first direct evidence that imazamox metabolism in these biotypes is P450-mediated, also in one population without an altered target site. Additionally, it was further confirmed that enhanced metabolism of 2,4-D in biotypes only HR to SAH or multiple HR to ALS inhibitors and SAH involves P450 as well. No metabolism was detected using the three inhibitors in all the herbicide-metabolizing P. rhoeas biotypes, suggesting that a common metabolic system involving P450s is responsible of degrading herbicides affecting both SoAs. Thus, selection pressure with either SAH or imidazolinone ALS inhibitors can select not only for resistance to each of them, but it can also confer cross-resistance between them in P. rhoeas.

Recent development of electrochemical advanced oxidation of herbicides. A review on its application to wastewater treatment and soil remediation

Herbicides have been largely utilized during the last decades to maintain the quality and quantity of agricultural crop, ensuring the need of an increasing world food production. However, these synthetic organics are highly biorecalcitrant and stable at mild conditions and cannot be effectively destroyed in conventional wastewater treatment facilities. Among the advanced oxidation processes used to remove herbicides, electrochemical technologies have been recently developed at bench scale as potential powerful treatments. This review presents a critical, exhaustive and detailed analysis on the application of single and combined electrochemical advanced oxidation processes to remediate wastewaters and soils contaminated with common herbicides, covering the period 2010–2019. Nine kinds of treatments, including single methods like anodic oxidation, anodic oxidation with electrogenerated H 2 O 2 , homogeneous and heterogeneous electro-Fenton, photoelectro-Fenton, solar photoelectro-Fenton and photoelectrocatalysis, as well as combined ones involving hybrid and sequential processes, have been examined. The fundamentals of each technology are briefly described, and the main results obtained for the removal of the most used herbicide families from synthetic solutions and soil-washing effluents are carefully exposed and discussed. The role of generated oxidizing agents and/or photolytic reactions in photo-assisted processes is explained to justify the mechanisms proposed for herbicide mineralization. The comparative oxidation ability of the different methods is discussed. Finally, future challenges remarking the need of treating real agricultural wastewaters and contaminated soils, the construction of electrochemical systems with stable electrodes at industrial scale and the realization of techno-economic studies are envisaged. • Review of 9 treatments with EAOPs for herbicide removal from wastewaters and soils (2010–2019). • Application of single and combined processes to synthetic herbicide solutions. • Rapid degradation of herbicides and overall mineralization feasible with BDD anodes. • Superiority of SPEF for wastewater treatment due to the positive action of sunlight irradiation. • Better performance for soil-washing effluents remediation by photoelectrolysis with UVC light.

Assessment of allelopathic compounds to develop new natural herbicides : A review

Herbicides are a crucial tool for weed control in crops. However, their continuous and indiscriminate uses have caused environmental pollution and development of weed resistance. Hence, there is an urgent need to minimise the dependence on synthetic herbicides. Allelopathy may be used to develop new bioherbicides to inhibit germination and growth of weeds. There is a great potential to develop eco-friendly herbicides from plants, but little research has been done so far in this context. Identification and quantification of natural weed control compounds (allelochemicals) of plants may help to develop natural herbicides (based on indigenous/invasive weed species), to reduce the dependence on synthetic herbicides and improve the integrated weed management programme in crops. This review describes thepotential allelochemicals present in plants, which may be used as a tool to develop new natural herbicides.

Integration of Sorghum [Sorghum bicolor (L.) Conard Moench.], Sunflower (Helianthus annuus L.) and Parthenium (Parthenium hysterophorus L.) Allelopathy for Weed Management in Maize under different Tillage Regimes.

Weed infestation is considered a significant yield reducing factor in maize yield around the world as well as in the south Asia. Integrated weed management (IWM) is recommended to reduce our reliance on synthetic herbicides and sustainable maize production. In this study, different tillage regimes and various allelopathic treatments were integrated for weed management in spring planted maize at Agricultural Research Station, Swabi (KP), Pakistan during spring both years 2014 and 2015. The experiment was laid out at silt loam soil in Randomized Complete Block Design (RCBD) with a split plot arrangement having three (03) replications. Different tillage regimes namely minimum, conventional, and deep tillage regimes were assigned to main plots (Factor A) and various allelopathic plants [Sorghum {

Digitaria insularis control by using herbicide mixtures application in soybean pre-emergence

Sourgrass (Digitaria insularis) is one of the main weeds in the soybean crop. In order to control its growth, an increase of herbicide rates is required to simplify its management as it a plant with high vegetative capacity and seed production. It implies to select the herbicide-resistent Digitaria insularis biotypes. Nevertheless, some information is still contrasting the antagonist of synthetic auxinic herbicides, associated with glyphosate and ACCase inhibitors mixtures, for the control of weeds resistant or tolerant to herbicides. This study aimed to evaluate the D. insularis control, with a mixture of herbicides applied in soybean pre-emergence, with sequential application in soybean post-emergence, and to check possible antagonism between ACCase inhibitors herbicides with synthetic auxins and other latifolicides. The experiment was conducted in Palotina, Paraná (Brazil) and Corpus Christi, Canindeyú, (Paraguay.) The treatments consisted of associations of glyphosate, ACCase inhibitors (clethodim, haloxyfop), and latifolicides (2,4-D, triclopyr, dicamba, carfentrazone, saflufenacil, chlorimuron). A randomized block design was used. Only in Palotina, the weed control was satisfactory after sequential application in post-emergence. An antagonism for all synthetic auxins was observed with glyphosate+clethodim or haloxyfop mixtures, in both locations. As a result, in Palotina an efficacious control of perennial D. insularis was found in pre-emergence burndown for some mixtures such as glyphosate+ACCase inhibitor added to carfentrazone, saflufenacil, or chlorimuron. Antagonism was observed for all synthetic auxins, in both locations. In Corpus Christi, the herbicide associations were not effective, even with the postemergence application in soybean of glyphosate+clethodim. With ineffective control for treatments composed with synthetic auxins, the post-emergence application in soybean increased the weed control with satisfactory final controls for all treatments.

Technological solutions for the cultivation of potatoes in the organic farming agroecosystem

One of the main tasks of organic production of agricultural products is to reduce the load on agroecosystems while simultaneously obtaining a yield indicator of high consumer quality, as with intensive production technologies, and this can be attained only through the fuller use of the biological potential of a crop, species, variety. In the production of agricultural products using biologized machine technologies, they interact with the environment: the atmosphere, hydrosphere and soil. The research is aimed to the creation of adaptive biologized machine technologies that ensure the efficient use of natural resources in the production of agricultural products with a minimum impact on the environment. The research object is the potato agrocenosis in the crop rotation of tilled and field crops. The crop rotation includes potatoes, beets, perennial legumes and cereals. In the experiment, potatoes of the Udacha variety (superelite), zoned for the Leningrad region, were cultivated. Particular attention was paid to the assessment of possible environmental risks in the implementation of the selected technological solutions for growing potatoes, as well as the fight against weeds, since the use of synthetic herbicides, fungicides, insecticides, etc. radically contradicts GOST 33980 - 2016 “Organic products. Rules for production, processing, labeling and sale”.

Adjuvant interference on spray solution properties of 2,4-D and dicamba herbicides and their efficacy for Ipomoea SPP. control

Synthetic auxin herbicides constitute major alternatives for managing tough-to-kill weeds such as Ipomoea spp. Adjuvant use is known to positively affect the biological efficacy of pesticides by modifying key spraying solution and droplet properties. Determining to what extent the use of adjuvants could change spray solution parameters and affect synthetic auxin herbicides’ efficiency for Ipomoea spp. control were the research goals. The study was conducted in two phases: laboratory and field, respectively. In the laboratory, the pH, the surface tension, and the resources of the herbicide drops were measured. In the field, weed control was evaluated. All adjuvants modified spray solution properties, lowering surface tension values. Most adjuvants decreased pH values as well as number and density of droplets due to an increase in droplet size. Regardless of adjuvant usage, Ipomoea spp. control levels rose more rapidly following 2,4-D spraying rather than dicamba, resulting in lower biomass accumulation when the former was used. Dicamba-containing treatments displayed slightly but significantly lower Ipomoea spp. control levels at the end of the evaluation period. Herbicide efficacy for Ipomoea spp. control was not improved upon the addition to the spray solution of any of the tested adjuvants. Adjuvant use altered spraying solution and droplet properties. 2,4-D spraying allowed for lower Ipomoea spp. biomass and greater control levels relative to dicamba, suggesting it might constitute a better option for Ipomoea spp. control. Even though herbicide efficacy was not improved with adjuvants, their use should still be considered given favorable spraying solution alterations, mainly with some alteration in droplet sizes despite the use of similar spray nozzles tips - maintaining weed control efficacy.

Phytotoxic Effects of Plant Essential Oils: A Systematic Review and Structure-Activity Relationship Based on Chemometric Analyses.

Herbicides are natural or synthetic chemicals used to control unwanted plants (weeds). To avoid the harmful effects of synthetic herbicides, considerable effort has been devoted to finding alternative products derived from natural sources. Essential oils (EOs) from aromatic plants are auspicious source of bioherbicides. This review discusses phytotoxic EOs and their chemical compositions as reported from 1972 to 2020. Using chemometric analysis, we attempt to build a structure-activity relationship between phytotoxicity and EO chemical composition. Data analysis reveals that oxygenated terpenes, and mono- and sesquiterpenes, in particular, play principal roles in the phytotoxicity of EOs. Pinene, 1,8 cineole, linalool, and carvacrol are the most effective monoterpenes, with significant phytotoxicity evident in the EOs of many plants. Caryophyllene and its derivatives, including germacrene, spathulenol, and hexahydrofarnesyl acetone, are the most effective sesquiterpenes. EOs rich in iridoids (non-terpene compounds) also exhibit allelopathic activity. Further studies are recommended to evaluate the phytotoxic activity of these compounds in pure forms, determine their activity in the field, evaluate their safety, and assess their modes of action.

Determination of allelopathic properties of Acacia catechu (L.f.) Willd.

Plants possessing allelopathic potential could be used as a source of bio-herbicide to help decrease the use of synthetic herbicides. Acacia catechu (L.f.) Willd., a deciduous tree from the Mimosaceae family, has been reported to have medicinal properties. However, there have been no reports on the allelopathy of this tree. Therefore, the leaf extracts of A. catechu were examined for allelopathic potential using six concentrations: 0.001, 0.003, 0.01, 0.03, 0.1, and 0.3 g dry weight equivalent extract mL-1. The aqueous methanol extracts of A. catechu significantly suppressed the seedling growth of six test plants such as alfalfa, cress, lettuce, barnyard grass, Italian ryegrass, and timothy. The extracts inhibited the six test plants in a concentration-dependent manner. The shoot and root growth of all the test plant species were completely inhibited from the concentration of 0.3 g of dry weight equivalent extract mL-1, except the shoot growth of barnyard grass. Concentrations needed for 50% growth inhibition (I50 values) ranged from 0.004 to 0.043 g dry weight equivalent extract mL-1 for shoot growth, and 0.003 to 0.019 g dry weight equivalent extract mL-1 for root growth. Moreover, the I50 values indicated that the root growth of all the test plants was more susceptible to the A. catechu extracts than the shoot growth. The inhibitory effects of the extracts of A. catechu suggest that the extracts may contain allelopathic potential and, therefore, may be a potential candidate for the isolation and characterization of allelochemicals to develop an ecofriendly bio-herbicide.

Influence of hard water on 2,4-D formulations for the control of dandelion

AbstractThe herbicide 2,4-D is used in a variety of cropping systems, especially in grasses because it is a selective postemergence broadleaf herbicide. However, the most common formulation (2,4-D dimethylamine) is antagonized when mixed in hard water. The objective of this research was to determine which formulations of 2,4-D or premixes of various formulations of synthetic auxin herbicides are subject to hard water antagonism. Formulations surveyed for hard water antagonism in the first experiment included 2,4-D dimethylamine, 2,4-D diethanolamine, 2,4-D monomethylamine, 2,4-D isopropylamine salt, 2,4-D choline salt, 2,4-D isooctyl ester, and 2,4-D ethylhexyl ester. Synthetic auxin formulation types in the second experiment included water-soluble, emulsifiable concentrates and emulsion-in-water. All formulations were mixed with both soft and hard water (600 mg CaCO3 L−1) and applied to dandelions to determine whether antagonism occurred in hard water. Water-soluble (amine and choline) 2,4-D formulations were antagonized by hard water, but water-insoluble (ester) 2,4-D formulations were not antagonized. Similar results were found by formulation type with water-soluble synthetic auxin premixes antagonized but emulsifiable concentrates not antagonized. Furthermore, water-soluble salt formulations were not antagonized when formulated in premixes with other synthetic auxin herbicides as an emulsion-in-water. This research demonstrates that all 2,4-D water-soluble formulations and water-soluble premixes with phenoxycarboxylic acid herbicides are subject to hard water antagonism. Formulations of 2,4-D containing emulsifying agents protect against antagonism by the water-insoluble nature of ingredients in their formulation.

Transcriptome analysis identified the mechanism of synergy between sethoxydim herbicide and a mycoherbicide on green foxtail

Certain synthetic herbicides can act synergistically with specific bioherbicides. In this study, a sethoxydim herbicide at 0.1× label rate improved biocontrol of herbicide-sensitive green foxtail (Setaria viridis, GFT) by Pyricularia setariae (a fungal bioherbicide agent), but did not change the efficacy on a herbicide-resistant GFT biotype. Reference transcriptomes were constructed for both GFT biotypes via de novo assembly of RNA-seq data. GFT plants treated with herbicide alone, fungus alone and herbicide + fungus were compared for weed-control efficacy and differences in transcriptomes. On herbicide-sensitive GFT, sethoxydim at the reduced rate induced ABA-activated signaling pathways and a bZIP transcription factor 60 (TF bZIP60), while improved the efficacy of biocontrol. The herbicide treatment did not increase these activities or improve biocontrol efficacy on herbicide-resistant plants. An exogenous application of ABA to herbicide-sensitive plants also enhanced bZIP60 expression and improved biocontrol efficacy, which supported the results of transcriptome analysis that identified the involvement of ABA and bZIP60 in impaired plant defense against P. setariae. It is novel to use transcriptome analysis to decipher the molecular basis for synergy between a synthetic herbicide and a bioherbicide agent. A better understanding of the mechanism underlining the synergy may facilitate the development of weed biocontrol.

The response of woody borreria (Hedyotis verticillata Lam.) towards curry leaves (Murraya koenigii (L.) Spreng.) aqueous extract at the vegetative growth

The massive used of synthetic chemical herbicides in crop production to meet the increasing demand had cause negativel impacts on the environment and ecosystem. Allelopathy approach of potential crops is a suitable alternative that should be explored to have sustainable weed management. The present study was conducted to determine the phytotoxic effect of aqueous curry leaves (Murraya koenigii (L.) Spreng.) extract on the emergence and seedling growth of the bioassay species, woody borreria (Hedyotis verticillata Lam.) under laboratory and nursery condition. The seed and seedling of bioassay species were treated with different concentration of aqueous curry leaves extract at 0, 20, 40, 60, 80 and 100g/L (laboratory) and 0, 50, 100, 150, 200 and 250g/L (nursery). The results showed that the aqueous curry leaves extract possesses a significant inhibition on seed emergence, shoot fresh weight and radicle length of H. verticillata at 100g/L concentration, where it reduced by almost 100% when applied as pre-emergence under laboratory condition. Meanwhile, the curry leaves extract at highest concentration of 250g/L significantly reduced the weed shoot fresh weight by 31% as compared to control and 50g/L concentration when treated at soil surface as post-emergence under nursery condition. Conversely, there is insignificant reduction in shoot height and root length of H. verticillata across all the applicate rates. These results suggest that curry leaves can be a good source to develop pre-emergence natural herbicide for weed management which is also eco-friendly for the environment and human beings.

Phytotoxic Effects and Mechanism of Action of Essential Oils and Terpenoids.

Weeds are one of the major constraints in crop production affecting both yield and quality. The excessive and exclusive use of synthetic herbicides for their management is increasing the development of herbicide-resistant weeds and is provoking risks for the environment and human health. Therefore, the development of new herbicides with multitarget-site activity, new modes of action and low impact on the environment and health are badly needed. The study of plant–plant interactions through the release of secondary metabolites could be a starting point for the identification of new molecules with herbicidal activity. Essential oils (EOs) and their components, mainly terpenoids, as pure natural compounds or in mixtures, because of their structural diversity and strong phytotoxic activity, could be good candidates for the development of new bioherbicides or could serve as a basis for the development of new natural-like low impact synthetic herbicides. EOs and terpenoids have been largely studied for their phytotoxicity and several evidences on their modes of action have been highlighted in the last decades through the use of integrated approaches. The review is focused on the knowledge concerning the phytotoxicity of these molecules, their putative target, as well as their potential mode of action.

Hairy buttercup (Ranunculus sardous) and cutleaf evening primrose (Oenothera laciniata) control using halauxifen-methyl based programs in Mississippi and Oklahoma winter wheat

AbstractHairy buttercup and cutleaf evening primrose are winter annual weeds that have become more problematic for winter wheat growers in the southern Great Plains and the midsouthern United States in recent years. Little research exists on which to base recommendations for controlling hairy buttercup in wheat, and little research has been published on cutleaf evening primrose control in recent years. With growing concerns of increased herbicide resistance among winter annual weeds, incorporating new herbicide sites of action has become necessary. The objective of this study was to assess halauxifen-methyl as a novel herbicide to control these two problematic winter annual broadleaf weeds in winter wheat in Mississippi and Oklahoma. Studies were conducted across four site-years in Mississippi and one site-year in Oklahoma comparing 15 herbicide programs with and without halauxifen-methyl. Hairy buttercup and cutleaf evening-primrose control was the greatest when a synthetic auxin was combined with an acetolactate synthase–inhibiting herbicide. Treatments including halauxifen-methyl resulted in the greatest control of hairy buttercup, whereas a synthetic auxin herbicide plus chlorsulfuron and metsulfuron resulted in the greatest control of cutleaf evening primrose. Halauxifen-methyl is an effective addition for control of winter annual broadleaf weeds like hairy buttercup and cutleaf evening primrose in winter wheat.

Buckhorn plantain (Plantago lanceolata) resistant to 2,4-D in Pennsylvania and alternative control options

AbstractBuckhorn plantain populations purportedly resistant to 2,4-D were identified in Pennsylvania following long-term, continual applications of the active ingredient to turfgrass. The research objectives of this study were to 1) confirm 2,4-D resistance with dose-response experiments, 2) confirm field resistance of buckhorn plantain to 2,4-D in Pennsylvania, and 3) evaluate alternative herbicides for 2,4-D-resistant buckhorn plantain. Greenhouse dose-response experiments evaluated the sensitivity of buckhorn plantain biotypes that were resistant or susceptible to 2,4-D, and to halauxifen-methyl, two synthetic auxin herbicides from different chemical families. The resistant biotype was ≥11.3 times less sensitive to 2,4-D than the susceptible biotype and required a 2,4-D dosage ≥4.2 times greater than the standard application rate to reach 50% necrosis. No cross-resistance was observed to halauxifen-methyl because both resistant and susceptible populations demonstrated similar herbicide sensitivity. Field experiments confirmed previous reports of ineffectiveness (≤30% reduction) with 2,4-D and other phenoxycarboxylic herbicides in potentially resistant buckhorn plantain biotypes. Treatments containing halauxifen-methyl resulted in a ≥70% reduction in resistant biotypes. This is the first known report of synthetic auxin herbicide resistance in any weed species in Pennsylvania and highlights emerging herbicide resistance challenges in turfgrass systems.

Structure-based virtual screening of bioherbicide candidates for weeds in sugarcane plantation using in silico approaches

Weeds in sugarcane have negatively affected the sugar yield rate. Several approaches have been carried out to overcome the weeds, including the usage of diuron as synthetic herbicide. However, the long-term usage of diuron is known to have a negative effect leads to the production of 3,4- Dichloroaniline responsible for soil leach and bioaccumulation. Therefore, this study aimed to find a potential natural herbicide. By mimicking the diuron's mode of action which inhibits the process of photosynthesis through blocking the Photosystem II protein D1 (psbA) of the weeds, fourteen compounds as potential candidate bioherbicides were virtually docked by PyRx v0.9.5 software to the specific site. Three important species of the weeds were chosen including Eleusine indica, Praxelis clematidea, and Momordica charantia. The binding affinity score was further calculated and ranked to screen the top six compounds as bioherbicide candidates. Interaction of each complex and the biological activity prediction were then performed by Discovery Studio software and PASS server, respectively. Aurachin P, Aurachin A, and Cyanobacterin were placed in the top ranked compounds with high binding affinity score around -6 to -9 kcal mol-1 toward the psbA. The amino acid interaction involved in the complex shows 50-90% similar to the control, psbA and diuron complex. Besides, the biological activity prediction of Aurachin P, Aurachin A, and Cyanobacterin exhibits the terms related to the inhibition of photosynthesis process via enzymatic pathway. Thus, the active compounds might have inhibition action in the photosynthesis process and control the weeds in sugarcane.

PEMANFATAAN EKSTRAK DAUN TANAMAN PULAI (Alstonia scholaris) SEBAGAI HERBISIDA NABATI UNTUK MENEKAN PERTUMBUHAN GULMA RUMPUT TEKI (Cyperus rotundus)

Alstonia scholaris contains flavonoids, tannins, triterpenoids, resins and alkaloids. Alkaloid compounds, tannins and flavonoids of plant origin can inhibit weed growth. Alkaloid compounds, tannins and flavonoids work by suppressing the hormone auxin and the hormone gibberelin so that weed growth is inhibited. This study aims to determine the potential of Alstonia scholaris leaves in inhibiting the growth of weed Cyperus rotundus. The inhibition of Cyperus rotundus growth can be seen from changes in leaf color/population phytotoxicity, number of leaves, and height of Cyperus rotundus. The research used Cyperus rotundus leaves which were mashed into flour and then extracted by macerating with alcohol 96% . The results of the extract of Cyperus rotundus leaf flour consisting of a concentration of 0 g/l (control), 25 g/l, 50 g/l, 75 g/l, and 100 g/l were applied to Cyperus rotundus. Pure extracts are given with different concentrations to determine the concentration that is effective in suppressing the growth of Cyperus rotundus. Vegetable herbicides of Cyperus rotundus leaves with a concentration of 50 g/l became the solution to control the enchanted grass weeds that are environmentally friendly without using synthetic herbicides. With the results of phytotoxicity P2= 40.00%, wet weight P2= 1.53 g, and dry weight P2= 0.91 g.

Potential Use of Biological Herbicides in a Circular Economy Context: A Sustainable Approach

In recent years, synthetic herbicides’ intense and disordered use has triggered severe contamination of soils and water bodies, causing damage to living organisms, including vegetal herbicide-resistance. In-part, biological herbicides, offer promise in addressing these problems, especially for sustainable weed management in both agricultural and natural resource management contexts. The search for culture media to serve as alternatives to the existing conventional synthetic media has focused on microalgae biomass. The natural properties of these organisms make them ideal raw materials for fermentative processes. Therefore, this study aimed to integrate bioprocesses producing bioherbicidal extract using a submerged fermentation process. For this, a substrate of microalgae recycled biomass to replace commercially used media for fungal growth for relatively cheap biomass obtained from wastewater phycoremediation after anaerobic treatment (UASB). We also verified its potential for weed control. Preliminary tests of microalgae fermentation were conducted in the raw and lyophilized form, using the fungus Trichoderma koningiopsis. To evaluate their phytotoxic potential, the biocompounds were applied to Bidens pilosa, Conyza bonariensis, Urochloa plantaginea, and Euphorbia heterophylla weeds. A central composite rotatable design (CCRD) was used to evaluate the influence of temperature (20–45oC), agitation (0–200 RPM), and pH (3–14) on the improvement of enzyme activities, fungal growth and the effects on Cucumis sativus germination tests. We found that microalgae could be used as a substrate for obtaining bioherbicides. The biocompounds produced in this study were relevant for pre- and post-emergence control of model plants (Cucumis sativus ), with vigor indexes of up to 8.05% and herbicide-resistant plants (Conyza bonariensis) with phytotoxic damage of up to 100% after 15 days. From the experiments’ design, we found that agitation was the variable that had the most significant effect on enzyme and biomass production, followed by pH and temperature. The enzymes also showed synergistic action when acting together with microalgae and fungi, potentiating the control effect on weeds. Finally, the system integrated bioprocesses through agro-industrial effluent recovery and reuse, considered one of the essential economic viability mechanisms by enhancing the development of more sustainable technologies that embrace the principles of a circular economy.

Colletotrichum siamense as a myco-biocontrol agent for management of the tridax daisy (Tridax procumbens)

The tridax daisy (Tridax procumbens) is a predominant weed in Thai plantations. Management of weeds in the country, both past and present, heavily relies on the use of synthetic herbicides. Here, we demonstrate the use of a phytopathogen for controlling this weed. The fungus Colletotrichum siamense isolate Cs1 was isolated from a diseased false daisy (Eclipta prostrata). Topical application of a conidial suspension of this fungus on Tridax procumbens plants led to 78–100% disease incidence on days 14–18 post-inoculation. Similar testing in the laboratory and greenhouse settings showed that C. siamense isolate Cs1 was non-pathogenic to cassava (Manihot esculenta) and eight other crops. Fluorescence microscopy of green fluorescent protein-expressing C. siamense indicated that the conidia germinated and formed appressoria for penetration on days 1–7 post-inoculation. Scanning electron microscopy showed hyphae growing on the leaf surface as well as invading the host through stomata. Trichomes of weed leaves served as important infection sites for this myco-pathogen. Oval conidia and pseudohyphae were detected inside the leaf trichomes, indicating that these cell types could help spread the fungus throughout the weed. C. siamense sporulated at high rates, at 1.7 × 1010 conidia/g, on a rice-oat mixture, suggesting a potential production recipe for commercialization. These data suggest that this weed-pathogenic fungus has potential as a bioherbicide for biological control of this weed.

EVALUACIÓN DE LA CAPACIDAD DE CAMBIO DE LOS SISTEMAS GANADEROS DE CAMPECHE HACIA UN MODELO DE PRODUCCIÓN ORGÁNICA

<p><strong>Background. </strong>In Campeche, Mexico, livestock takes place in generally unfertilized grasslands and acahuales, where cattle rarely receive veterinary treatment. These characteristics suggest that some livestock producers could adopt organic production, but their availability for adoption is uncertain and there is little information to assess their feasibility.<strong> Objective.</strong> Evaluate the change capacity of the conventional livestock systems of Campeche with respect to the organic production model and specify the critical points in management that must be improved in the transition to organic farming.<strong> Methodology.</strong> Semi-structured interviews were conducted with 74 livestock producers belonging to the BioPaSOS-CATIE Campeche project, in locations in the municipalities of Escárcega, Champotón and Calakmul, as well as direct observations in cattle ranches. The information obtained was used in the Multi-criteria Organic Livestock Conversion Index (OLCI); built with 10 indicators and 35 variables.<strong> Results.</strong> OLCI showed a low level, but close to the intermediate level of organic standards. Indicators close to standards were: breeds and reproductive management, soil fertilization and feed management. Indicators that move away were: herd safety, ecological weed control in pastures and crops, pest and disease control in pastures and crops, veterinary prevention and treatment, animal welfare, sustainable pasture management and ecological management. <strong>Implications.</strong> The results obtained are useful for livestock producers in the state of Campeche, since strategies can be generated that allow the conversion of their production systems to an organic livestock model. They are also a benchmark for future research related to the subject of sustainability assessment or organic livestock using indicators. <strong>Conclusions. </strong>The evaluated livestock systems presented a low level of conversion to the organic production model. Critical points in management that hinder the transition to organic livestock are: sanitary hygiene control, application of synthetic herbicides and insecticides, breastfeeding up to eight months, appropriate stocking rate, use of a silvopastoral system and mainly advisory and training for organic certification, organic development plan and certification, internal control of the organic process and incentives for organic livestock production.</p>