Herbicide Dalapon Research Articles

Reduced graphene oxide-Fe3O4-TiO2 nanocomposite catalyst for the mineralization of herbicide dalapon by heterogeneous photoelectro-Fenton process

Fast degradation and complete mineralization of herbicide dalapon (DPN) as the target pollutant has been investigated for the first time by the heterogeneous photoelectro-Fenton (hPEF) process using a nitrogen doped reduced graphene oxide (NrGO) modified carbon felt (CF) cathode (NrGO@CF) and a ternary nanocomposite catalyst (TNC) based on reduced graphene oxide (rGO), Fe3O4, and TiO2 to maintain high yield generation of H2O2 and •OH. The effects of main variables, including the catalyst composition and amount, applied current, and initial pH of the solution, were investigated. The as-synthesized nanomaterials exhibit significant improvements thanks to their high specific surface area, increased H2O2 production, catalytic activity, and the possibility to work in a wide pH range. This system also promotes photoreduction and photooxidation reactions by increasing photon absorption. By combining highly conductive carbon materials and the photoexcited electrons from TiO2, redox cycling between ≡FeII and ≡FeIII was facilitated, thus improving the process performance. Catalytic stability measurements show that the use of a NrGO@CF cathode, an equimass rGO-Fe3O4-TiO2 TNC and boron doped diamond (BDD) anode trio resulted in the fast degradation and complete mineralization of DPN within 30 and 60 minutes, respectively, after five consecutive cycles under UV light irradiation, 500 mA current intensity, 0.1 g L−1 catalyst concentration and pH 6 conditions. Moreover, intermediate products of DPN oxidation were identified. Therefore, this study highlights an efficient and stable cathode and catalyst duo for the removal of a short chain halogenated aliphatic herbicide from aqueous media.

Characterisation of a Bacterium from Selat Tebrau and Screening of Microbial Genomes for Dehalogenases

Current study was to investigate the presence of dehalogenase in the isolated bacterium from Selat Tebrau that can grow on 2,2-dichloropropionic acid (2,2-DCP is an active compound in herbicide Dalapon®). Strain RN1, a Gram-negative and rod in shape was tentatively identified as Enterobacter cancerogenus based on basic biochemical and the 16S rRNA gene analyses. The calculated cells doubling time were 5.29 hours based on growth of the bacterium in liquid minimal media with 10, 20 and 30 mM of 2,2-DCP, respectively. However, no growth was observed at 40 mM 2,2-DCP liquid minimal medium due to increase in 2,2-DCP toxicity. It was hypothesized that, strain RN1 produced dehalogenase(s) which merits a further study of the genomic data of the same genus and species available in the database. A putative dehalogenase, designated as DehRN was located in the published data of Enterobacter cancerogenus. Pairwise of DehRN amino acids with known dehalogenase resulted in sequence identity of <20%, suggesting a new class of dehalogenase enzyme in the Enterobacter cancerogenus.Keywords: 2,2-DCP, dehalogenase, dichloropropionate, Enterobacter, haloalkanoic acid

The response of myxogastrids to soil amendments

Myxogastrids (also referred to as myxomycetes or plasmodial slime moulds) are common to abundant organisms in soils, where they probably account for ~50% of the protozoan component represented by soil amoebae. In the present study, an effort was made to assess the possible effects of various soil amendments on myxogastrids, which exemplify the role of soil protozoans while also being relatively easy to quantify in soil samples. Amendments to soil in either field or microcosm experiments included the addition of water, glucose, a bacterial suspension and the herbicide Dalapon. Both trophic forms and encysted forms of myxogastrids were considered. As general observation, the responses of myxogastrids to the various amendments were distinct in the case of the herbicide, with the most obvious effect being the ratio of trophic to encysted forms. Any assessment of soil protozoans invariably will result in occasions where the population is grossly underestimated if samples are not tested after freezing as well as fresh. Frozen samples provide data on the total encysted population, which appears to “awakened” by the action of freezing.

Degradation of Millimolar Concentration of the Herbicide Dalapon (2,2-Dichloropropionic Acid) by Rhizobium Sp. Isolated from Soil

ABSTRACTThe herbicide Dalapon is widely used in agricultural areas and is persistent in ground water. A Rhizobium sp. was able to grow at 0.2 mM 2,2-dichloropropionic acid (2,2DCP), which was 100-fold lower than the concentration of the substrate routinely used. Apparently, no new dehalogenases are required to allow growth on this low concentration of 2,2DCP as judged by electrophoretic mobility of dehalogenase proteins in native-PAGE analysis and protein separation by anion-exchange column chromatography. The kinetic analysis suggested that the known dehalogenases were able to act efficiently on low concentrations of haloalkanoic acids. The amount of each dehalogenase, from cells grown on low substrate concentration was different compared to that seen at 20 mM 2,2DCP due to complex regulatory controls, which respond to the growth environment.

The occurrence of the herbicide dalapon (2,2-dichloropropionate) in potable water as a disinfection by-product

Salts of 2,2-dichloropropionic acid, such as dalapon, are well known as herbicides and are regulated as such in potable water in Australia and elsewhere. It is also an identified disinfection by-product (DBP), but little is known about the compound's formation and typical levels from this source. This work presents results from a sampling campaign where 2,2-dichloropropionate was found at levels between 0.1 and 0.5 µg l(-1) in potable water samples from a major treatment plant in South East Queensland, Australia. However, levels were below the reporting limit (0.01 µg l(-1)) in the immediate source water for the plant. Also, temporal trends in 2,2-dichloropropionate observed in treated water during sampling mirrored those of trihalomethanes albeit at much lower concentrations, suggesting that the occurrence is due to in situ formation as a DBP. This could present a regulatory dilemma in some jurisdictions.

A screening level fate model of organic contaminants from advanced water treatment in a potable water supply reservoir

Augmentation of potable water sources by planned indirect potable reuse of wastewater is being widely considered to address growing water shortages. Environmental buffers such as lakes and dams may act as one of a series of barriers to potable water contamination stemming from micropollutants in wastewater. In South-East Queensland, Australia, current government policy is to begin indirect potable reuse of water from reverse osmosis equipped advanced water treatment plants (AWTPs) when the combined capacity of its major storages is at 40% capacity. A total of 15 organic contaminants including NDMA and bisphenol A have been publically reported as detected in recycled water from one of South-East Queensland’s AWTPs, while another 98 chemicals were analysed for, but found to be below their detection limit. To assess the natural attenuation in Lake Wivenhoe, a Level III fugacity based evaluative fate model was constructed using the maximum concentrations of these contaminants detected as input data. A parallel aquivalence based model was constructed for those contaminants, such as dichloroacetic acid, dalapon and triclopyr, which are ionised in the environment of Lake Wivenhoe. A total of 247 organic chemicals of interest, including disinfection by-products, pesticides, pharmaceuticals and personal care products, xenoestrogens and industrial chemicals, were evaluated with the model to assess their potential for natural attenuation. Out of the 15 detected chemicals, trihalomethanes are expected to volatilise with concentrations in the outflow from the dam approximately 400 times lower than influent from the AWTPs. Transformation processes in water are likely to be more significant for NDMA and pharmaceuticals such as salicylic acid and paracetamol as well as for caffeine and the herbicides dalapon and triclopyr. For hydrophobic contaminants such as cholesterol and phenolic xenoestrogens such as 4-nonylphenol, 4-t-octylphenol and bisphenol A, equilibrium between water and sediments will not be attained and hence fate processes such as removal in outflow are predicted to become relatively important.

A plant selectable marker gene based on the detoxification of the herbicide dalapon

A gene from Pseudomonas putida coding for a dehalogenase capable of degrading 2,2 dichloropropionic acid (2,2DCPA), the active ingredient of the herbicide dalapon, has been isolated and characterised. In plant transformation experiments the gene was shown to confer resistance to 2,2DCPA at a tissue culture level where 2,2DCPA could be used to select for transformants. At the whole plant level, transformed plants showed resistance to 2,2DCPA at concentrations up to 5 times the recommended dose rate of dalapon when it was sprayed on their leaves. At lower concentrations, the herbicide caused a non-lethal yellowing of sensitive plants which clearly distinguished them from resistant plants. The mode of action of chlorinated aliphatic acids is not known but they probably affect many enzyme pathways. The results described here are the first example of engineering a plant resistant to a herbicide that does not have one specific enzyme as its target site. This gene has several advantages as a marker in plant breeding and genetic studies. For example, the herbicide is readily available and has low toxicity, transformants can be selected at both the tissue culture and the whole plant level, a large number of transformed plants can easily be screened even in the field, and there is a very low probability of selecting spontaneous mutants.

Degradation of aliphatic halogen-substituted pesticides by dehalogenase isolated from Pseudomonas alcaligenes. Identification and properties of the enzyme

Some characteristics of a 2,2-dichloropropionate dehalogenase induced in a bacterial strain capable of degrading high concentrations of the herbicide dalapon were studied. Polyacrilamide gel electrophoresis of the crude cell free extracts identified only one type of dehalogenase. The single enzymatic protein showed activity against a variety of chlorinated aliphatic acids but differed in their activity levels. Thus activity in μmol substrate converted (mg protein) −1 min −1 was 2-monochloropropionate 0.65, 2,2-dichloropropionate 0.56, 2-monochloroacetate 1.70 and 2,2-dichloroacetate 1.00. In the crude extracts, the enzyme activity against 2,2-dichloropropionate was optimal at a broad pH range with a mid-point at pH 9.5 and apparent K m values were within the range 0.23–0.73 mM.

Herbicide-induced resistance of cotton to Verticillium wilt disease and activation of host cells to produce the phytoalexin gossypol

Pretreating cotton seeds with selected herbicide markedly increased cotton resistance to vascular wilt caused by Verticillium albo-atrum. The present investigation studied the mechanism of resistance to V. albo-atrum induced by some herbicides in susceptible cotton plants. The three herbicides tested repressed mycelial growth. Prometryn and dalapon caused a marked reduction in the appearance of Verticillium wilt disease and were the most effective in controlling the disease. Phytoalexin (gossypol) production was greatly increased in herbicide-treated inoculated cotton plants. The level of gossypol was higher in the root than stem. Maximum production of gossypol was achieved in cotton plants treated with the herbicides prometryn and dalapon and inoculated with fungal spores but it was not present in uninoculated control plants. Key words: cotton, Verticillium albo-atrum, herbicides, phytoalexin, disease resistance.

Response of selected soilborne fungi and bacteria to herbicides utilized in potato crop management systems in Maine

The response of nine soilborne fungi associated with potato production:Rhizoctonia solani, Fusarium solani ‘Coerculeum,’F. roseum ‘Sambucinum,’F. avenaceum, Helminthosporium solani, Verticillium alboatrum, Alternaria solani, Trihcoderma viride, andLaetisaria arvalis; and five soilborne bacteriaAzotobacter chroococcum, Bacillus subtilis, Erwinia carotovora subsp. carotovora,Pseudomonas aeruqinosa andPseudomonas fluorescens to the herbicides linuron, metribuzin, dinoseb, paraquat, EPTC, and dalapon were determined by growth on amended media. None of the herbicides increased radial growth of the fungi, and only dinoseb significantly (P = 0.05) reduced radial growth of all fungi at concentrations less than 64 ppm. EPTC, dalapon, linuron, paraquat, and dinoseb severely inhibited bacterial survival (91, 82, 44%, respectively) when evaluated on trypticase soy and cimmons citrate agar media amended with herbicides at concentrations of 1, 10, and 100 ppm. Dinoseb, when applied to field soil in pots, significantly reduced total microorganism populations in the top 5 cm of soil. Results suggest that soil applications of herbicides can selectively inhibit soil microflora with possible effects on disease incidence and severity, and may also be a factor in determining effectiveness of biolgical control agents.

The use of thermal calendar models to improve the efficiency of herbicide applications in Sorghum halepense (L.) Pers

Summary:The dynamics of sprout emergence and rhizome populations of Sorghum halepense (L.) Pers. were followed in two field experiments. In addition, the herbicide dalapon was applied at various stages during rhizome development and the degree of control was evaluated. Rhizome biomass oscillated during the growth cycle, whereas the number of rhizome sprouts increased asymptotically until mid‐summer. Observed values were compared against those predicted from a thermal calendar model. The dynamics of the rhizome population was predicted accurately in both experiments, but only in one of them was the prediction of the sprout emergence satisfactory. The degree of control differed markedly between herbicide applications at various intervals during population development. Best results were obtained from applications when rhizome biomass was at a minimum. The time of minimum biomass was predicted by a thermal calendar model. The advantages of using the thermal calendar model to determine the time of herbicide application, and the possible influence of the distribution of the rhizome population in the soil profile on the predictions of the model, are discussed.

Cultivation and weed control for aspen seedling establishment in the southern Rocky Mountains

Containerized aspen (Populustremuloides Michx.) seedlings were planted at high-elevation sites in southern (May 1982) and northern (July 1983) New Mexico. Each plantation compared fall cultivation (20 cm depth), prior to planting the following spring or summer, with cultivation at the time of planting. Subtreatments of the tests included applications of the postemergent herbicide dalapon and the preemergents linuron, trifluralin, or simazine applied 2 to 3 weeks before planting. First season survival exceeded 75% for the best treatment at each site. Cultivation, in general, effectively reduced weed cover and improved seedling success. Fall cultivation, in particular, improved seedling survival and growth only at the relatively dry southern site. Except for spring-cultivated plots in the south, some herbicide applications improved weed control and seedling performance over cultivation alone. The combination of fall cultivation plus trifluralin is considered the best site preparatory treatment tested.

Effects of dalapon and TCA on the growth and yield of oilseed rape (Brassica napus)

SUMMARYThe tolerance of oilseed rape (Brassica napus cv. Jet Neuf) to the herbicides dalapon and TCA was studied in two series of 10 experiments over four years. TCA (7.6–30.4 kg a.i./ha) was applied pre‐emergence and dalapon (2.9–11.6 kg a.i./ha) was sprayed post‐emergence between September and November at two growth stages (2–5, 4–7 leaves). Dalapon at all doses caused the leaves to appear yellow‐green in colour and at the higher rates (5.8–11.6 kg a.i./ha), especially when applied at the later of the two growth stages, scorched the leaf margins and stunted the plants. TCA also caused the leaves to appear yellow‐green and was noted to affect the retention of water by the leaf surfaces. In general the visible effects of treatment with dalapon were more severe than those of TCA.The effects of these two herbicides on rape seed yields were variable, with some trials showing statistically significant reductions and others none. However by combining the results of trials with similar treatments some underlying trends were identified. In the overall analyses dalapon at 11.6 kg a.i./ha, applied at both growth stages and at 5.8 kg a.i./ha, applied at the later one, reduced yields significantly. TCA at 15.2, 22.8 and 30.4 kg a.i./ha also caused significant yield reductions in the combined analyses. Further statistical analysis questioned the safety of the lower rates of both herbicides, which were similar to those recommended by the manufacturers. The severity of the foliar damage caused by dalapon was well correlated with the risk of significant yield reductions but not with the actual percentage loss of yield. No such correlations were possible with TCA as the visual symptoms were similar on all sites and were unaffected by dose.Recent changes in agricultural practices and in crop cultivar do not appear to have altered the sensitivity of rape to dalapon and TCA appreciably.

Laboratory Toxicity of Pesticides to Geocoris pallens (Hemiptera: Lygaeidae), a Predator in California Cotton

The acute toxicity of 22 pesticides used on cotton was determined on adult Geocoris pallens Stal. Pesticide residues were tested on cotton leaf, paper, and glass surfaces to establish a procedure for evaluating toxicity. Highest mortality was caused by residues on glass; lowest mortality was caused by residues on paper. Tests of residues on leaves are recommended as standard tests to determine pesticide toxicity to G. pallens because leaf residues gave LD50 values that were between the mortality values obtained for the low and highest recommended field rates. The technique was used to identify pesticides with low predator toxicity. Methomyl, methidathion, and carbaryl were less harmful than most chemicals tested; propargite and dicofol were least toxic. Fenvalerate was more toxic than acephate, and acephate was more toxic than methomyl when predators were exposed to these residues on Empoasca sp. The herbicides glyphosate and DSMA and the defoliants DEF and mer ph os had low acute toxicity. High mortalities caused by the herbicides dalapon and MSMA and the defoliant paraquat dichloride suggested that, to spare seasonal and overwintering predator populations, other chemicals should be used. The fungicides sulfur and benomyl were almost nontoxic at recommended dose rates, but the soil fumigant metham sodium caused moderate mortality. Pesticides least toxic to G. pallens are recommended for use in cotton pest management.

Influence of different pre-emergence herbicides on cotton diseases caused byRhizoctonia solani andFusarium oxysporum f. sp.vasinfectum

Field experiments were carried out during 1978–1982 in different provinces in Egypt to study the side effects of different pre-emergence herbicides (trifluralin, dinitramine, fluometuron, diuron, dalapon, and prometryn) at three different concentrations (1/2X, 1X, and 2X of recommended dose) onRhizoctonia solani andFusarium oxysporum f. sp.vasinfectum incidence. All the tested herbicides did not affect significantlyR. solani disease incidence. Fusarium disease incidence was reduced significantly by the higher concentrations of all the tested herbicides. Prometryn and dalapon showed to be effective ones. No additive effects on diseases incidence could be detected due to the herbicide treatments. All the tested herbicides did not affect significantly the resistance of cotton plants to Fusarium infection, the soluble carbohydrates and amino acids exuded by cotton seedlings, and the saprophytic activity ofFusarium oxysporum f.sp.vasinfectum. Chlamydospore germination in soil was inhibited by the higher concentrations of all the tested herbicides. Prometryn and dalapon which showed to be the most effective herbicides in inhibiting chlamydospore germination in soil, were the most effective ones in reducing the disease in field.

Effects of pesticides on soil microflora using dalapon as an example.

Effects of the herbicide dalapon on the soil microflora are evaluated. Measurements were made on populations and pure cultures of micro-organisms, dehydrogenase and phosphatase, soil respiration, and nitrogen transformations. At normal concentrations of 2.6 and 26 ppm, dalapon had little effect and is unlikely to harm the soil microflora or soil fertility. At abnormal concentrations of 266 and 2,660 ppm, marked effects occurred on the microflora and its activities. In one soil, 2,660 ppm dalapon significantly increased production of ammonium-nitrogen; nitrification was almost totally inhibited in this soil. The results are discussed in terms of the validity of the tests for detecting effects of pesticides on the soil microflora. Some problems, particularly of data interpretation and evaluation, are high-lighted.

The life cycle and growth of Sialis lutaria L. (Megaloptera) in a drainage channel under different methods of plant management

Abstract. 1. The life cycle of Sialis lutaria in two experimental reaches, one treated with the herbicides dalapon and 2,4‐D (Chemical) and the other subjected to a conventional method of plant control (Hand), of a drainage channel in Essex took about 2 years.2. A maximum density of 815 m‐2 was recorded and the density of each year class in both reaches generally decreased exponentially with age.3. At certain times of the year the mean individual weight of each year class increased exponentially with age. Annual production was estimated to be 985 (Hand) and 1171 (Chemical) mg dry weight m‐2, with ratios of annual production to mean standing crop (P: b̄) of 1.6 and 1.8 respectively.4. There was no evidence that the use of herbicides had any discernible effect on the mortality, growth or production of S.lutaria.

The influence of temperature and moisture on the effects of the herbicide dalapon on nitrogen transformations in soil

The herbicide dalapon, at 2660 parts/10 6 in four soils, generally inhibited nitrification and stimulated mineralization of N. These effects of dalapon cannot be used to judge the likely effect of the chemical in the field in view of the abnormal concentration used. However, the modification of these effects by environmental factors can be validly assessed. The results were modified by soil characteristics, moisture content and temperature. Different effects were found in samples from different fields on the same soil and in similar crop rotations. The degradation of the herbicide was markedly affected by soil type. The significance of the results is discussed in relation to the requirements of the chemical registration and approval authorities for information on the side-effects of agricultural chemicals on the soil microflora.

Effect of herbicides on epicuticular wax of winter oilseed rape ( Brassica napus) and infection by Pyrenopeziza brassicae

Foliar sprays of the herbicides dalapon, carbetamide and propyzamide on winter oilseed rape (Brassica napus L. ssp. oleifera) can decrease the amount and alter the form of epicuticular wax on leaves. This effect was most marked with dalapon where it occurred on sprayed leaves and those affected by translocated herbicide. It was evident under controlled environment and field conditions up to at least 3 months after treatment. Decreased wax on leaves was associated with increased wettability which favours spore deposition and encouraged infection by Pyrenopeziza brassicae (Cylindrosporium concentricum). Benomyl gave useful but incomplete control of this fungus on rape when applied in winter and early spring before stem extension. The use of herbicides and fungicides on winter rape is discussed in relation to disease control and yield.

Dalapon resistance at an early seedling stage in Lolium perenne

AbstractThe inhibitory effect of the herbicide dalapon on germination and shoot elongation was evaluated in two perennial ryegrass cultivars, Melino RvP and Cropper. These cultivars had been shown to be dalapon resistant and susceptible, respectively, in a previous comparison of 14‐week‐old plants.Dalapon (10‐2 and 10‐3 m) significantly reduced rates of germination and shoot elongation to the same extent in both cultivars.It is suggested that the effects of dalapon on germination and shoot elongation during the first 9 days of development are not indicative of levels of resistance in more mature plants.