Phytochemical Investigation of Cuscuta campestris Yunck. Stem Extract and Evaluation of Its Bioherbicidal Effect on Amaranthus retroflexus L. and Portulaca oleracea L.

This study focused on characterizing chemically and evaluating in vitro allelopathic and bioherbicidal potential of secondary metabolites extracted from the stem of Cuscuta campestris in seed germination, early seedling growth and early plant growth of Amaranthus retroflexus and Portulaca oleracea. The combined effects of stem extract and a reduced dose of herbicide metribuzin were also examined. Plant extract contained 17 phenolic compounds and the most abundant phenols were flavonoids: quercetin, (+)-catechin, daidzin, luteolin, and rutin. The seeds of P. oleracea were less sensitive than the seeds of A. retroflexus. The seed bioassay confirmed the inhibitory effect of stem extract on germination and early growth of both weed seedlings at concentrations of 0.75 % and 1 %, and a minor inhibitory effect in the plant bioassay. On the other hand, a synergy of C. campestris stem extract and metribuzin was revealed, as their combination achieved better results in the control of both weed species. Based on obtained data C. campestris stem extract could be a potential source of natural-based weed control molecules.

Effects of mixtures of allelopathic plant water extracts and a herbicide on weed suppression.

The present study investigated integrated effects of two allelopathic plant water extracts (WE) (Ambrosia artemisiifolia [AMBEL] and Xanthium strumarium [XANST]) and a herbicide (mesotrione) on morphological (height and fresh weight of plants) and physiological (pigments content) parameters of Abutilon theophrasti and Chenopodium album. Also, the study aimed to identify the main components of AMBEL and XANST WE and to evaluate their potential allelopathic effects. Of the 18 investigated compounds, 13 were detected in both tested WE, and p-coumaric acid was the leading component in AMBEL, while quinic acid was the predominant component of XANST. The WE of both weed species and their mixtures with the herbicide exhibited more powerful allelopathic effects on fresh weight and content of pigments than on the height of A. theophrasti and C. album. The results showed that all measured parameters of both weeds were inhibited in treatments with mesotrione and its mix with AMBEL and XANST WE. The data revealed a highly significant difference in effects (P < 0.05) between control weeds and those treated with AMBEL WE and mesotrione, where the inhibition of fresh weight was over 90%, while the inhibition of pigments content exceeded 80%, and plant height was inhibited by over 70%.

Phenolic Compounds and Allelopathic Potential of Fermented and Unfermented Wheat and Corn Straw Extracts.

Total phenolic (TPC) and flavonoid (TFC) content, individual phenolic compounds and antioxidant activities of methanol extracts of wheat and corn straw were determined. Germination bioassay was conducted with Abutilon theophrasti Medik., Asclepias syriaca L., and Chenopodium album L. seed. Samples were fermented by Lactobacillus plantarum and changes in TPC, TFC, antioxidant, and biological activity were investigated. TPC and TFC were significant in both samples and after fermentation their recovery was improved. All samples contain mainly quercetin, cinnamic acid, p-coumaric acid, and ferulic acid. Fermentation changed the content of phenolic and flavonoid compounds, differently in each case. All tested extracts showed high DPPH activity with IC50 being significantly lower for fermented samples. FRAP activity was also high. Crude straw extracts were overall more effective than fermented ones concerning inhibition of germination and seedlings growth, mainly without statistically significant differences between wheat and corn. Compared with mesotrione, extracts were more effective in germination and seedling growth inhibition of C. album and in seedling growth inhibition of A. theophrasti.

Evaluation of Lactobacillus plantarum and Saccharomyces cerevisiae in the Presence of Bifenthrin.

This work describes the effect of insecticide bifenthrin on Lactobacillus plantarum and Saccharomyces cerevisiae. Growths of used microorganisms in growth media supplemented with pesticide were studied. Determination of bacterial and yeast fermentation efficiency in wheat supplemented with bifenthrin was conducted. Additionally, investigation of bifenthrin dissipation during microbiological activity was performed. Experiments applying bifenthrin in different concentrations highlighted a negligible impact of the pesticide on the growth of L. plantarum and S. cerevisiae. This insecticide overall negatively affected the yeast fermentation of wheat, while its presence in wheat had a slight negative impact on lactic acid fermentation. The results of bifenthrin dissipation during lactic acid and yeast fermentations of wheat showed that activities of L. plantarum and S. cerevisiae caused lower pesticide reductions. Average bifenthrin residue reduction within samples fermented with L. plantarum was 5.4 % (maximum ~16 %), while within samples fermented with S. cerevisiae, it was 11.6 % (maximum ~17 %).

The potency of Saccharomyces cerevisiae and Lactobacillus plantarum to dissipate organophosphorus pesticides in wheat during fermentation.

The degradation behaviour of pirimiphos methyl with Saccharomyces cerevisiae and chlorpyrifos methyl with Lactobacillus plantarum in wheat during fermentation was studied. Yeast fermentation was especially effective for reduction of pirimiphos methyl applied at 5 mg kg-1 (maximum residue limit-MRL) causing dissipation for max 48.8%. Pesticide reduction rate decreased with an increase of fortification rate. Thus in samples fortified with 25 and 75 mg kg-1 a reduction up to 27.1%, and 23.7% respectively, was observed. Activity of L. plantarum was especially effective for reduction of chlorpyrifos methyl applied at 3 mg kg-1 (MRL) causing dissipation for max 56.7%. This reduction rate decreased with an increase of fortification rate. In samples contaminated with 15 and 45 mg kg-1 dissipation reached up to 38.6% and 34.7% respectively. For both experiments, initial inoculums sizes had no statistically significant effect on pesticides dissipation level, while concerning fermentation temperatures at all fortification levels the highest degradations occurred at 30 °C. Overall, regardless fermentation parameters, the degradation rate constants of pirimiphos methyl fermented with yeast were increased comparing with control samples by 255-573, 56-116 and 119-594% in samples contaminated at MRL, 5MRL and 15MRL of pesticide, while the degradation rate constants of chlorpyrifos methyl fermented with lactobacilli were increased by 74-769, 59-237 and 46-469% respectively. These results evidenced that yeast and lactobacilli played an important role in promoting pirimiphos methyl i.e. chlorpyrifos methyl dissipation in wheat.

Stability of the pyrethroid pesticide bifenthrin in milled wheat during thermal processing, yeast and lactic acid fermentation, and storage.

BACKGROUND: Pesticide residues have become an unavoidable part of food commodities. In the context of increased interest for food processing techniques as a tool for reducing pesticide residues, it is interesting to study the potential loss of pesticides during lactic acid and yeast fermentation. In the present paper the effect of fermentation by Lactobacillus plantarum and Saccharomyces cerevisiae and storage on 23 °C on bifenthrin in wheat was investigated. In addition, the effect of sterilisation (applied in order to avoid contamination with wild microorganism strains, i.e. to determine the individual effects of used strains) on bifenthrin degradation was tested as well. RESULTS: No significant loss of bifenthrin was observed during storage, or after the sterilisation. During the lactic acid fermentation, reduction within wheat fortified with 0.5 mg kg(-1) was 42%, while quite lower within samples fortified with 2.5 mg kg(-1) , maximum 18%. In contrast, bifenthrin concentration was not reduced during yeast fermentation, as the reduction in fortified samples was in the range of spontaneous chemical degradation during incubation period. CONCLUSION: Possible bifenthrin contamination in wheat, in amounts over the maximum residue limits, could not be reduced by sterilisation or by yeast fermentation, but lactic acid fermentation could be an effective tool for minimising residual contamination.

Characterization of the clomazone sorption process in four agricultural soils using different kinetic models.

Kinetic studies are important for understanding the parameters and processes involved in the sorption of pesticides to soil. Considering the agricultural and environmental relevance of clomazone, its sorption kinetics was studied in four agricultural soils (Regosol, Planosol, Chernozem and Vertisol) at two concentrations (0.5 and 15 mg L-1). Different kinetic models were applied to the experimental data. The pseudo-second-order model described the data much better than the hyperbolic and pseudo-first-order models, and the kinetic rate constants indicated concentration-dependent clomazone sorption kinetics. The application of the two-site nonequilibrium model (TSNE) revealed a more time-dependent sorption of the lower clomazone concentration than that of the higher clomazone concentration, and the greatest concentration impact occurred in Regosol. Elovich and intraparticle diffusion models predicted more intensive sorption during the slower second phase and that sorption kinetics is governed more by mass transfer across the boundary layer than by a intraparticle diffusion process at higher clomazone concentration. Intraparticle diffusion is the rate-controlling process in Regosol at lower concentration, while this process and the boundary layer control the sorption kinetics in other soils. Significant correlations between some kinetic parameters and soil properties indicate an impact of the soil texture on the clomazone sorption mechanism, which must be considered in assessing the clomazone leaching behavior.

Liquid-solid sample preparation followed by headspace solid-phase microextraction determination of multiclass pesticides in soil.

This paper describes development and validation of a multiresidue method for the determination of five pesticides (terbufos, prochloraz, chloridazon, pendimethalin, and fluorochloridone) belonging to different pesticide groups in soil samples by GC/MS, followed by its application in the analysis of some agricultural soil samples. The method is based on a headspace solid-phase microextraction method. Microextraction conditions, namely temperature, extraction time, and NaCI content, were tested and optimized using a 100 microm polydimethylsiloxane fiber. Three extraction solvents [methanol, methanol-acetone (1 + 1, v/v), and methanol-acetone-hexane (2 + 2 + 1, v/v/v)] and the optimum number of extraction steps within the sample preparation stage were optimized for the extraction procedure. LOD values for all the studied compounds were less than 12 microg/kg. Recovery values for multiple analyses of soil samples fortified at 30 microg/kg of each pesticide were higher than 64%. The method was proven to be repeatable, with RSD lower than 15%.

Phytotoxicity and allelopathic potential of Juglans regia L. leaf extract.

Implementation of plant extracts that are rich in phytochemicals and have the allelopathic potential for weed management could help reduce the use of chemical herbicides. The present study investigated the herbicidal potential of walnut (Juglans regia L.) leaf extract (WLE) against two weeds, Amaranthus retroflexus L. and Chenopodium album L., by testing in vitro their seed germination and seedling growth, and then evaluated in vivo the oxidative stress of potted plants. The effects of the walnut leaf extract were also tested on maize (Zea mays L.) to eliminate possible negative impacts on a cultivated plant. Total phenolic acids and total flavonoid content in the extract were determined in prior bioassays, followed by separation and analysis of flavonoids and phenolic acids by high-performance liquid chromatography (HPLC). Phytochemical analysis revealed that the obtained extract was notably rich in phenolic compounds, while HPLC analysis confirmed the presence of (+)-catechin, luteolin, myricetin, rutin, (-)-epicatechin, genistin, protocatechuic acid, and caffeic acid as major extract components. The results obtained in bioassays revealed a significant negative impact of the walnut leaf extract on germination and seedling growth of the tested weeds, as well as significant oxidative stress in weeds grown in pots. Although it affected the maize seedling growth in vitro similar to the tested weeds, maize germination was less sensitive to treatment, and the extract did not have a significant negative impact in terms of oxidative stress in maize plants grown in pots. The findings show that walnut leaf extract may have a promising role in replacing chemical herbicides in maize.

Effects of the technical ingredient clomazone and its two formulated products on aquatic macrophytes.

One active ingredient can be a component of different types of formulations of pesticides, while the toxicity of its formulations may vary depending on various constituents used in the mixture. The present study focuses on evaluating the effects of the active ingredient clomazone and its formulations (Rampa® EC and GAT Cenit 36 CS, both containing 360 g a.i./l of clomazone) on non-target aquatic macrophytes. The two formulation types differ in their active ingredient release and presumed environmental impact. In order to cover different ecological traits, two species of aquatic macrophytes - the floating monocot Lemna minor and the rooted dicot Myriophyllum aquaticum, were used as test models. The results of this study revealed differences in the sensitivity of tested plants to clomazone. Based on the most sensitive parameters, M. aquaticum proved to be more sensitive than L. minor to the technical ingredient and both formulations. The species sensitivity distribution (SSD) approach that was tried out in an attempt to create a higher tier step of risk assessment of clomazone for primary producers indicates that tests on rooted macrophytes can add value in risk assessment of plant protection products. The capsule formulation of clomazone was less toxic than the emulsion for L. minor, but more toxic for M. aquaticum. The most toxic for L. minor was the emulsifiable concentrate formulation Rampa® EC, followed by technical clomazone (EC50 33.3 and 54.0 mg a.i./l, respectively), while the aqueous capsule suspension formulation GAT Cenit 36 CS did not cause adverse effects. On the other hand, the most toxic for M. aquaticum was the formulation GAT Cenit 36 CS, followed by technical clomazone and the formulation Rampa® EC, demonstrating a greater effect of the capsule formulation.

Headspace solid phase microextraction method for determination of triazine and organophosphorus pesticides in soil.

A headspace solid phase microextraction method (HS-SPME) for simultaneous determination of five pesticides belonging to triazine and organophosphorus pesticide groups in soil samples was developed. Microextraction conditions, such as temperature, extraction time and sodium chloride (NaCl) content were investigated and optimized using 100 microm polydimethyl-siloxane (PDMS) fiber. Detection and quantification were done by gas chromatography-mass spectrometry (GC-MS). Relative standard deviation (RSD) and recovery values for multiple analysis of soil samples fortified at 30 microg kg(- 1) of each pesticide were below 13 % and higher than 70 %, respectively. Limits of detection (LOD) for all the compounds studied were less than 3.2 microg kg(- 1). The proposed method was applied in the analysis of some agricultural soil samples.

A method for reducing environmental pollution by using essential oils in rodent pest management program.

Strong-smelling plant extracts, such as essential oils, have a variety of feeding effects on mammals. Considering current concerns over long-term health issues and environmental effects of chemicals, plant-based products with repellent or antifungal activities may represent good solutions for improvement of rodent pest control programs. The present study was therefore focused on examining the effects of bergamot, lavender, and thyme essential oils as additional bait components on daily intakes of cereal-based baits by wild house mice. Lavender essential oil, containing linalool and linalyl acetate as main components, and thyme essential oil with a prevailing thymol component had no effects on house mice diet. Bergamot essential oil, whose main components were linalool, limonene, and linalyl acetate, showed a repellent effect on house mouse diet.