azoxystrobin and epoxiconazole

Pesticides constitute an integral part of today's agriculture. Their widespread use leads to ubiquitous contamination of the environment, including soils. Soils are a precious resource providing vital functions to society - thus, it is of utmost importance to thoroughly assess the risk posed by widespread pesticide contamination. The exposure of non-target organisms to pesticides in soils is challenging to quantify since only a fraction of the total pesticide concentration is bioavailable. Here we measured and compared the bioavailable and total concentrations of three fungicides - boscalid, azoxystrobin, and epoxiconazole - and evaluated which concentration best predicts effects on nine microbial markers. The experiments were performed in three different soils at five time points over two months employing nearly 900 microcosms with a model plant. The total and bioavailable concentrations of azoxystrobin and boscalid decreased steadily during the trial to levels of 25 % and 8 % of the original concentration, respectively, while the concentration of epoxiconazole in soil nearly remained unchanged. The bioavailable fraction generally showed a slightly faster and more pronounced decline. The microbial markers varied in their sensitivity to the three fungicides. Specific microbial markers, such as arbuscular mycorrhizal fungi, and bacterial and archaeal ammonia oxidizers, were most sensitive to each of the fungicide treatments, making them suitable indicators for pesticide effects. Even though the responses were predominantly negative, they were also transient, and the impact was no longer evident after two months. Finally, the bioavailable fraction did not better predict the relationships between exposure and effect than the total concentration. This study demonstrates that key microbial groups are temporarily susceptible to a single fungicide application, pointing to the risk that repeated use of pesticides may disrupt vital soil functions such as nutrient cycling in agroecosystems.

Topics: Fungicides, Industrial; Mycorrhizae; Pesticides; Soil; Soil Microbiology; Soil Pollutants

Slow-release fungicide formulations (azoxystrobin, epoxiconazole, and tebuconazole) shaped as pellets and granules in a matrix of biodegradable poly(3-hydroxybutyrate) and natural fillers (clay, wood flour, and peat) were constructed. Infrared spectroscopy showed no formation of chemical bonds between components in the experimental formulations. The formulations of pesticides had antifungal activity against

Topics: Clay; Delayed-Action Preparations; Drug Carriers; Drug Compounding; Epoxy Compounds; Fungicides, Industrial; Fusarium; Hydroxybutyrates; Kinetics; Polyesters; Pyrimidines; Soil; Strobilurins; Triazoles; Wood

Crop protection agents are widely used in modern agriculture and exert direct effects on non-target microorganisms such as yeasts. Yeasts abundantly colonize wheat grain and affect its chemical composition. They can also limit pathogen growth. This study evaluated the sensitivity of yeast communities colonizing winter wheat kernels to benzimidazole, strobilurin, triazole and morpholine fungicides, trinexapac-ethyl, a commercial mixture of o-nitrophenol+p-nitrophenol+5-nitroguaiacol, and chitosan applied during the growing season of winter wheat and in vitro in a diffusion test. A molecular identification analysis of yeasts isolated from winter wheat kernels was performed, and nucleotide polymorphisms in the CYTb gene (G143A) conferring resistance to strobilurin fungicides in yeast cells were identified. The size of yeast communities increased during grain storage, and the total counts of endophytic yeasts were significantly (85%) reduced following intensive fungicide treatment (fenpropimorph, a commercial mixture of pyraclostrobin, epoxiconazole and thiophanate-methyl). This study demonstrated that agrochemical residues in wheat grain can drive selection of yeast communities for reduced sensitivity to xenobiotics. A mutation in the CYTb gene (G143A) was observed in all analyzed isolates of the following azoxystrobin-resistant species: Aureobasidium pullulans, Debaryomyces hansenii, Candida albicans and C. sake. Agrochemicals tested in vitro were divided into four classes of toxicity to yeasts: (1) tebuconazole and a commercial mixture of flusilazole and carbendazim - most toxic to yeasts; (2) fenpropimorph and a commercial mixture of pyraclostrobin and epoxyconazole; (3) propiconazole, chitosan, thiophanate-methyl and a commercial mixture of o-nitrophenol, p-nitrophenol and 5-nitroguaiacol; (4) trinexapac-ethyl and azoxystrobin - least toxic to yeasts. It was found that agrochemicals can have an adverse effect on yeast abundance and the composition of yeast communities, mostly due to differences in fungicide resistance between yeast species, including the clinically significant C. albicans.

Topics: Agaricales; Agrochemicals; Ascomycota; Benzimidazoles; Candida albicans; Carbamates; Drug Resistance, Fungal; Epoxy Compounds; Fungicides, Industrial; Microbial Sensitivity Tests; Pesticide Residues; Plant Diseases; Pyrimidines; Seasons; Silanes; Strobilurins; Triazoles; Triticum; Xenobiotics; Yeasts

Improved retention and distribution of agrochemicals on plant surfaces is an important attribute in the biological activity of pesticide. Although retention of agrochemicals on plants after spray application can be quantified using traditional analytical techniques including LC or GC, the spatial distribution of agrochemicals on the plants surfaces has received little attention. Matrix assisted laser desorption/ionization (MALDI) imaging technology has been widely used to determine the distribution of proteins, peptides and metabolites in different tissue sections, but its application to environmental research has been limited. Herein, we probed the potential utility of MALDI imaging in characterizing the distribution of three commercial fungicides on wheat leaf surfaces. Using this MALDI imaging method, we were able to detect 500 ng of epoxiconazole, azoxystrobin, and pyraclostrobin applied in 1 μL drop on the leaf surfaces using MALDI-MS. Subsequent dilutions of pyraclostrobin revealed that the compound can be chemically imaged on the leaf surfaces at levels as low as 60 ng of total applied in the area of 1 μL droplet. After application of epoxiconazole, azoxystrobin, and pyraclostrobin at a field rate of 100 gai/ha in 200 L water using a track sprayer system, residues of these fungicides on the leaf surfaces were sufficiently visualized. These results suggest that MALDI imaging can be used to monitor spatial distribution of agrochemicals on leaf samples after pesticide application.

Topics: Epoxy Compounds; Fungicides, Industrial; Imaging, Three-Dimensional; Limit of Detection; Methacrylates; Plant Leaves; Pyrimidines; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Strobilurins; Triazoles; Triticum

In intensive agriculture areas the use of pesticides can alter soil properties and microbial community structure with the risk of reducing soil quality.. In this study the fatty acid methyl esters (FAMEs) evolution has been studied in a factorial lab experiment combining five substrates (a soil, two aged composts and their mixtures) treated with a co-application of three pesticides (azoxystrobin, chlorotoluron and epoxiconazole), with two extraction methods, and two incubation times (0 and 58 days). FAMEs extraction followed the microbial identification system (MIDI) and ester-linked method (EL).. The pesticides showed high persistence, as revealed by half-life (t1/2) values ranging from 168 to 298 days, which confirms their recalcitrance to degradation. However, t1/2 values were affected by substrate and compost age down to 8 days for chlorotoluron in S and up to 453 days for epoxiconazole in 12M. Fifty-six FAMEs were detected. Analysis of variance (ANOVA) showed that the EL method detected a higher number of FAMEs and unique FAMEs than the MIDI one, whereas principal component analysis (PCA) highlighted that the monosaturated 18:1ω9c and cyclopropane 19:0ω10c/19ω6 were the most significant FAMEs grouping by extraction method. The cyclopropyl to monoenoic acids ratio evidenced higher stress conditions when pesticides were applied to compost and compost+soil than solely soil, as well as with final time.. Overall, FAMEs profiles showed the importance of the extraction method for both substrate and incubation time, the t1/2 values highlighted the effectiveness of solely soil and the less mature compost in reducing the persistence of pesticides.

Topics: Environmental Monitoring; Epoxy Compounds; Fatty Acids; Half-Life; Methacrylates; Pesticides; Phenylurea Compounds; Pyrimidines; Soil; Soil Microbiology; Strobilurins; Time Factors; Triazoles

Three trials were carried out during springs 2003 and 2004 to compare the distribution of fungicides on the different leaf layers of wheat plants. Mixtures of 1 L/ha of Amistar (SC, 250 g/L of azoxystrobin) and 1 L/ha of Opus (SC, 125 g/L of epoxiconazol) were applied using two experimental sprayers carried by hand and three farmer's sprayers (including a Hardi TwinFlow one). Working pressure, speed, boom length, nozzles, volume of mixture per hectare were specific to each material. One to six days after the treatments, leaf samples were collected at each canopy level and the amount of both active ingredients was determined using gas chromatography with electron capture detection (GC-ECD). The distribution pattern of the fungicides on the different leaf layers was not affected by the spraying system. In the same way, neither the used equipments, nor the mixture volume per hectare, nor the air flow of the Hardi TwinFlow sprayer did not significantly influence the distribution of fungicide.

Topics: Agriculture; Chromatography, Gas; Dose-Response Relationship, Drug; Epoxy Compounds; Fungicides, Industrial; Methacrylates; Pesticide Residues; Plant Leaves; Pyrimidines; Strobilurins; Triazoles; Triticum

Populations of the causal agent of wheat tan spot, Pyrenophora tritici-repentis, that are collected from fields frequently treated with reduced fungicide concentrations have reduced sensitivity to strobilurin fungicides and azole fungicides (C14-demethylase inhibitors). Energy-dependent efflux transporter activity can be induced under field conditions and after in vitro application of sublethal amounts of fungicides. Efflux transporters can mediate cross-resistance to a number of fungicides that belong to different chemical classes and have different modes of action. Resistant isolates can grow on substrata amended with fungicides and can infect plants treated with fungicides at levels above recommended field concentrations. We identified the hydroxyflavone derivative 2-(4-ethoxy-phenyl)-chromen-4-one as a potent inhibitor of energy-dependent fungicide efflux transporters in P. tritici-repentis. Application of this compound in combination with fungicides shifted fungicide-resistant P. tritici-repentis isolates back to normal sensitivity levels and prevented infection of wheat leaves. These results highlight the role of energy-dependent efflux transporters in fungicide resistance and could enable a novel disease management strategy based on the inhibition of fungicide efflux to be developed.

Topics: Acrylates; Ascomycota; ATP-Binding Cassette Transporters; Drug Resistance, Fungal; Epoxy Compounds; Flavones; Fungicides, Industrial; Gene Expression Regulation, Fungal; Methacrylates; Microbial Sensitivity Tests; Phenylacetates; Plant Diseases; Plant Leaves; Pyrimidines; Strobilurins; Triazoles; Triticum

The effects of single fungicide applications on Mycosphaerella graminicola (septoria leaf blotch) control and winter wheat yield were evaluated in field trials conducted in central Belgium between 2000 and 2004. Individual applications of 25, 50, 75 and 100% of the manufacturer's recommended dose rates of azoxystrobin and epoxiconazole, and all the combinations of these treatments, were made at GS 39 in 2001 to 2004 and at GS 59 in 2000. Disease assessments were made at growth stage 75, some 7-8 weeks after the last applications. Between 2000 and 2003, no significant difference was observed for disease control between the products when applied alone. With regard to the dose responses, the differences between the recommended dose rates and the 50% reduced dosages were not important. In 2004, azoxystrobin was less effective than epoxiconazole. This was probably the result of strobilurin-resistant isolates of M. graminicola reaching an occurrence of 32% before fungicide application. The combination of different dosages of azoxystrobin and epoxiconazole revealed that there was very little synergy between these products when applied in a single application. The combinations of these products were better than individual applications only when high dosages of both compounds were used.

Topics: Ascomycota; Dose-Response Relationship, Drug; Drug Resistance, Fungal; Drug Synergism; Epoxy Compounds; Fungicides, Industrial; Methacrylates; Plant Diseases; Plant Leaves; Pyrimidines; Strobilurins; Time Factors; Triazoles; Triticum

A total of 740 Mycosphaerella graminicola strains were isolated between 2000 and 2002 from winter wheat F1 or F2 leaves showing Septoria leaf blotch lesions (SLB) collected mainly at the soft dough stage in fungicide trials, analysing at 12 locations in Belgium the possibilities and risks associated with the use of epoxiconazole and azoxystrobin at various doses, mixtures and application dates. Fungicide sensitivity tests were performed in microtitre plates on potato dextrose broth amended with various concentrations of azoxystrobin. A wide range of sensitivity to azoxystrobin was observed, with EC50 values ranging for 735 strains between 0.002 to 0.7 microg/ml, the highest frequency gradually shifting from EC50 classes 0.01 and 0.02 microg/ml azoxystrobin in 2000 to EC50 classes 0.02 and 0.04 microg/ml in 2002. No clear selection effect of particular fungicide use strategies was observed. Among the 382 strains isolated in 2002, five originating from 2 locations, showed azoxystrobin EC50 values >1 microg/ml. On medium amended with 100 microg/ml salicylhydroxamic acid (SHAM), 58% of the 2002 strains were strongly inhibited, which affected adequate azoxystrobin ED50 determination. This suggests widespread occurrence of M. graminicola strains relying in vitro on the alternative respiration pathway. In the presence of SHAM, strains 339 and 880 showed azoxystrobin EC50 values of 3 and >30 microg/ml, respectively. This high level of resistance to a QoI fungicide was confirmed by analysing mycelium growth inhibition on PDA. Cross-resistance to trifloxystrobin and kresoxim-methyl was demonstrated. Greenhouse assays on wheat plants revealed that control of QoI resistant strains by azoxystrobin is decreased, compared to control of sensitive ones. This highlights the risk of resistance to QoI fungicides also in M. graminicola populations, although up to now no decrease in field performance was noticed. It is recommended to delay build up of QoI resistance by an integrated approach, combining optimised fungicide use with the choice of SLB resistant cultivars and the application of farming practices promoting stubbles break down and so the reduction of the teleomorph stage.

Topics: Acrylates; Ascomycota; Belgium; Cell Respiration; Dose-Response Relationship, Drug; Drug Resistance, Fungal; Epoxy Compounds; Fungicides, Industrial; Methacrylates; Microbial Sensitivity Tests; Plant Diseases; Pyrimidines; Strobilurins; Triazoles; Triticum

Strobilurin fungicides have a broad spectrum activity against all major foliar pathogens of wheat. In addition to this extraordinary fungicidal activity side-effects have been reported which result in higher yields of cereals, e.g. the reduction of respiration, delayed leaf senescence, activation of nitrogen metabolism as well as increased tolerance against abiotic stress factors. In the vegetation period 2000/2001 field trials were carried out at three sites in North Rhine-Westphalia to study the effects of three strobilurin fungicides on the yield formation of six winter wheat varieties. The strobilurins were applied two times as the commercial products Stratego (trifloxystrobin + propiconazole), Amistar/Pronto Plus (azoxystrobin/spiroxamine + tebuconazole) and Juwel Top (kresoxim-methyl + epoxiconazole + fenpropimorph. Fungicide-treated plants were kept disease-free by an initial azole-application in GS 31 in order to exclude disease effects on physiological parameters relevant to yield formation. Photosynthetic electron transport of strobilurin-treated wheat, was improved as early as at GS 65 compared to azole-treated plants. Differences often increased with growth stage and were closely related to a delay in leaf senescence. A higher photosynthetic activity of strobilurin-treated plants was confirmed by gas exchange and chlorophyll fluorescence measurements under field conditions. The yield benefit of wheat from strobilurin treatments varied from 2% to 9% depending on an improved photosynthetic capacity due to a higher and/or prolonged activity. Neither yield potential nor disease susceptibility of the cultivar had an effect on the height of the extra yield which, in contrast was modified by location and wheat genotype.

Topics: Acetates; Acrylates; Azoles; Chlorophyll; Epoxy Compounds; Fungicides, Industrial; Germany; Imines; Methacrylates; Morpholines; Phenylacetates; Photosynthesis; Pyrimidines; Strobilurins; Triazoles; Triticum

Two modern fungicides, a strobilurin, azoxystrobin (AZO), and a triazole, epoxiconazole (EPO), applied as foliar spray on spring barley (Hordeum vulgare L. cv. Scarlett) 3 days prior to fumigation with injurious doses of ozone (150-250 ppb; 5 days; 7 h/day) induced a 50-60% protection against ozone injury on leaves. Fungicide treatments of barley plants at growth stage (GS) 32 significantly increased the total leaf soluble protein content. Additionally, activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate-peroxidase (APX) and glutathione reductase (GR) were increased by both fungicides at maximal rates of 16, 75, 51 and 144%, respectively. Guiacol-peroxidase (POX) activity was elevated by 50-110% only in AZO treated plants, while this effect was lacking after treatments with EPO. This coincided with elevated levels of hydrogen peroxide (H2O2) only in EPO and not in AZO treated plants. The enhancement of the plant antioxidative system by the two fungicides significantly and considerably reduced the level of superoxide (O2*-) in leaves. Fumigation of barley plants for 4 days with non-injurious ozone doses (120-150 ppb, 7 h/day) markedly and immediately stimulated O2*- accumulation in leaves, while H2O2 was increased only after the third day of fumigation. Therefore, O2*- itself or as precursor of even more toxic oxyradicals appears to be more indicative for ozone-induced leaf damage than H2O2. Ozone also induced significant increases in the activity of antioxidant enzymes (SOD, POX and CAT) after 2 days of fumigation in fungicide untreated plants, while after 4 days of fumigation these enzymes declined to a level lower than in unfumigated plants, due to the oxidative degradation of leaf proteins. This is the first report demonstrating the marked enhancement of plant antioxidative enzymes and the enhanced scavenging of potentially harmful O2*- by fungicides as a mechanism of protecting plants against noxious oxidative stress from the environment. The antioxidant effect of modern fungicides widely used in intense cereal production in many countries represents an important factor when evaluating potential air pollution effects in agriculture.

Topics: Acrylates; Antioxidants; Environmental Exposure; Enzyme Induction; Epoxy Compounds; Fungicides, Industrial; Hordeum; Methacrylates; Oxidants, Photochemical; Oxidative Stress; Ozone; Plant Leaves; Pyrimidines; Reactive Oxygen Species; Strobilurins; Triazoles

Quantitative PCR and visual monitoring of Mycosphaerella graminicola epidemics were performed to investigate the effect of curative and preventative applications of azoxystrobin in wheat field crops. A non-systemic protectant and a systemic curative fungicide, chlorothalonil and epoxiconazole, respectively, were used as references. PCR diagnosis detected leaf infection by M graminicola 3 weeks before symptom appearance, thereby allowing a clear distinction between curative and preventative treatments. When applied 1 week after the beginning of infection, azoxystrobin curative activity was intermediate between chlorothalonil (low effect) and epoxiconazole. When applied preventatively, none of the fungicides completely prevented leaf infection. There was some indication that azoxystrobin preventative treatments may delay fungal DNA increase more than epoxiconazole at the beginning of leaf infection. Both curative and preventative treatments increased the time lapse between the earliest PCR detection and the measurement of a 10% necrotic leaf area. Azoxystrobin only slightly decreased the speed of necrotic area increase compared with epoxiconazole. Hence, azoxystrobin activity toward M graminicola mainly resides in lengthening the time lapse between the earliest PCR detection and the measurement of a 10% necrotic leaf area. Information generated in this way is useful for optimal positioning of azoxystrobin treatments on M graminicola.

Topics: Acrylates; Ascomycota; DNA, Fungal; Epoxy Compounds; Fungicides, Industrial; Methacrylates; Nitriles; Plant Diseases; Plant Leaves; Polymerase Chain Reaction; Pyrimidines; Strobilurins; Time Factors; Triazoles; Triticum