kresoxim-methyl and epoxiconazole

Pesticide transport from seed dressings toward subsurface tile drains is still poorly understood. We monitored the neonicotinoid insecticides imidacloprid and thiamethoxam from sugar beet seed dressings in flow-proportional drainage water samples, together with spray applications of bromide and the herbicide S-metolachlor in spring and the fungicides epoxiconazole and kresoxim-methyl in summer. Event-driven, high first concentration maxima up to 2830 and 1290 ng/L for thiamethoxam and imidacloprid, respectively, were followed by an extended period of tailing and suggested preferential flow. Nevertheless, mass recoveries declined in agreement with the degradation and sorption properties collated in the groundwater ubiquity score, following the order bromide (4.9%), thiamethoxam (1.2%), imidacloprid (0.48%), kresoxim-methyl acid (0.17%), S-metolachlor (0.032%), epoxiconazole (0.013%), and kresoxim-methyl (0.003%), and indicated increased leaching from seed dressings compared to spray applications. Measured concentrations and mass recoveries indicate that subsurface tile drains contribute to surface water contamination with neonicotinoids from seed dressings.

Topics: Agriculture; Beta vulgaris; Bromides; Chromatography, High Pressure Liquid; Environmental Monitoring; Epoxy Compounds; Groundwater; Herbicides; Imidazoles; Insecticides; Methacrylates; Neonicotinoids; Nitro Compounds; Oxazines; Phenylacetates; Seeds; Soil; Soil Pollutants; Spectrometry, Mass, Electrospray Ionization; Strobilurins; Thiamethoxam; Thiazoles; Triazoles; Water Pollutants, Chemical

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

During the 2000-2001 season a field trial was conducted with the aim of quantifying the distribution and persistence of epoxiconazole and kresoxlm-methyl in the different leaf layers of winter wheat plants. In the case of applications before flag leaf emergence, the redistribution of the two active ingredients in the newly formed leaves following the applications was also measured. Allegro (125 g/L epoxiconazole and 125 g/L kresoxim-methyl, SC) was applied at the manufacturer's recommended rate (1 L/ha) either in a single treatment at stages GS32, GS39 and GS59 or in 2, 3 or 4 split applications. Following spraying, leaf samples were collected over time, from each leaf layer, and the two active ingredients were quantified by gas chromatography with electron capture detection (GC-ECD). Fungicide distribution varies according to time of application. A descending gradient through the leaves was observed in the case of application at GS59. When sprayed at stage GS39, on the other hand, the second leaf intercepted more fungicide than the flag leaf. Kresoxim-methyl was found to degrade faster than epoxiconazole. With split treatments, the last spraying appears to be very significant in terms of final fungicide quantities. Redistribution appears possible, especially in the case of epoxiconazole, though in very small quantities.

Topics: Chromatography, Gas; Epoxy Compounds; Fungicides, Industrial; Methacrylates; Pesticide Residues; Phenylacetates; Plant Leaves; Strobilurins; Time Factors; 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