Soil metabolism of the herbicide isoxaben in winter wheat crops

Rouchaud, Jean; Gustin, F.; Callens, Danny; Vanhimme, M; Bulcke, Robert

doi:10.1021/jf00035a060

Cited by 12 publications

(14 citation statements)

References 6 publications

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“…This growth could explain why the compound did not accumulate in the medium. However, as previously reported,6 the presence of demethoxyisoxaben and of 2‐hydroxy‐6‐methoxybenzamide in soil treated with isoxaben suggests a modification of the phenyl ring before hydrolysis of the amide bond of isoxaben. This hypothesis is supported by the study of a chloridazon‐degrading bacteria transforming metamitron to 2‐dihydroxy‐metamitron which was then cleaved by meta ‐fission 20…”

Section: Resultssupporting

confidence: 72%

“…In their previous study, Rouchaud et al 6 also reported the presence of 3‐(1‐ethyl‐1‐methylpropyl) isoxazol‐5‐ylamine in soil extract, but the compound did not accumulate and they therefore considered the possibility of an unusual mechanism for amide hydrolysis with 5‐isoxazolone accumulation. Our results suggest that 3‐(1‐ethyl‐1‐methylpropyl)isoxazol‐5‐ylamine could be an important intermediary product of the microbial degradation of isoxaben in soil.…”

Section: Resultsmentioning

confidence: 99%

“…These authors observed that N ‐[3‐(1‐hydroxy‐1‐methylpropyl)isoxazol‐5‐yl]‐2,6‐dimethoxybenzamide, the major metabolite detected during their laboratory soil study, reached levels of approximately 20% of the applied isoxaben. In their study, Rouchaud et al 6 identified demethoxy‐isoxaben, 5‐isoxazolone (3‐[1‐ethyl‐1‐methylpropyl]isoxazolin‐5‐one) and 2,6‐dimethoxybenzamide as the three main metabolites of isoxaben in the soil of winter wheat crops treated with the herbicide. Three minor compounds, 5‐aminoisoxazole [3‐(1‐ethyl‐1‐methylpropyl)isoxazol‐5‐ylamine], 2‐hydroxy‐6‐methoxybenzamide and 2,6‐dimethoxybenzoic acid were also detected.…”

Section: Introductionmentioning

confidence: 99%

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Isolation and characterization of efficient isoxaben‐transforming Microbacterium sp strains from four European soils

Arrault¹,

Desaint²,

Catroux³

et al. 2002

Pest Management Science

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Nutrient-agar plates containing isoxaben (500 mg litre(-1)) were used to isolate isoxaben-metabolising bacteria from four European soils incubated with the herbicide under laboratory conditions. In flask experiments, inoculation of a basal salts medium containing nitrogen and [phenyl-U-14C]isoxaben with an isolate (B2b) resulted in 33% recovery of the initial radioactivity as [14C]carbon dioxide after 2 weeks. A major metabolite identified by GC-MS and NMR analysis as 3-(1-ethyl-1-methylpropyl)isoxazol-5-ylamine accumulated both in basal salts and nutrient broth media. 2,6-Dimethoxybenzoic acid, a suspected metabolite of isoxaben, was not detected in either liquid media. However, the capability of the B2b isolate to use 2,6-dimethoxybenzoic acid as a source of carbon was demonstrated. Soil inoculation with the B2b strain resulted in an increase in the recovery of [14C] carbon dioxide from both [phenyl-U-14C] and [isoxazole-5-14C]isoxaben. The metabolite identified as 3-(1-ethyl-1-methylpropyl)isoxazole-5-ylamine only accumulated if the soil was autoclaved before inoculation. This metabolite was rapidly mineralized by the microflora of a natural soil without history of isoxaben treatment. Homology patterns of sequenced 16S rDNA between isoxaben-transforming isolates and reference strains showed that the four isolates identified belonged to the genus Microbacterium.

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Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Isolation and characterization of efficient isoxaben‐transforming Microbacterium sp strains from four European soils

Arrault¹,

Desaint²,

Catroux³

et al. 2002

Pest Management Science

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“…The herbicidal activity of isoxaben was not lost following shallow incorporation into the soil, and> 75% of the compound remained in the top 0 to 7.5 em of the soil (Colbert and Ford 1987). Soil degradation of isoxaben is primarily through microbial activity (Rouchaud et al 1993). Solar breakdown of isoxaben has also been reported in aquatic systems (Mamouni et al 1992).…”

Section: Introductionmentioning

confidence: 98%

Duration of Broadleaf Weed Control with Isoxaben Using Soil Bioassays

Chandran

Derr

1998

Weed technol.

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A soil bioassay experiment was conducted in Blacksburg, VA, to determine the effect of isoxaben application timings and rates on duration of weed control. Flats containing soil were imbedded into the field. Isoxaben was applied in the spring, fall, and spring followed by fall (double application) at 0.56, 0.84, and 1.12 kg ai/ha. Flats were moved to a greenhouse at 0, 1, 3, 6, and 9 months after treatment (MAT) and seeded with yellow rocket, buckhorn plantain, and spotted spurge for the bioassays. Weed counts from treated flats were compared to those in untreated flats to determine percent control. Fall and spring followed by fall applications provided approximately 20% greater control of yellow rocket 3 MAT and 30% greater control 6 MAT, compared to a single spring application of isoxaben. Isoxaben at all rates controlled yellow rocket > 70% at 6 mo after fall application. At 3 MAT, fall and spring plus fall-applied isoxaben provided about 15 and 20% greater buckhorn plantain control, respectively, compared to spring application. The two highest rates of isoxaben controlled buckhorn plantain > 70% at 3 mo after fall application, but provided poor control at 6 MAT. Control of spotted spurge was similar among the three application timings for isoxaben and was unacceptable at most evaluation dates. Overall, isoxaben applied at 1.12 kg/ha provided better control of all three weed species for a longer time than the reference herbicide, oxadiazon, applied at 3.36 kg/ha.

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“…Onto each plot, one (and always the same) of the different organic fertilizers treatments schemes 1 to 5 was applied repeatedly during this 30 years period In previous work we observed that the soil persistence of the herbicide diflufenican (1; N-(2,4-difluorophenyl)-2-[3-(trifluoromethyl)phenoxy]-3-pyridinecarboxamide) in winter wheat crop was increased when one of the organic fertilizers green manure, pig slurry or cow manure had been applied some days before sowing. 1 The organic amendments slowed down the whole diflufenican soil metabolism, as the soil concentrations of its herbicide metabolites 2 (2-[3-trifluoromethyl)phenoxy]-3-pyridinecarboxylic acid) and 3 (N-(2,4-difluorophenyl)-2-hydroxy-3-pyridinecarboxamide), and of its non herbicide metabolite 4 (2-hydroxy-3-carboxypyridine) were lower in the organic fertilizers treated plots than in the untreated ones. Application of the organic amendments one month before wheat sowing is frequent in the agronomy practice; especially with pig slurry, as problems exist for the elimination of the animal effluents in regions of intensive pig breeding.…”

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confidence: 96%

Past organic fertilizer treatments: Influence on the herbicide diflufenican soil metabolism in wheat crops

Rouchaud

Gustin

Callens

et al. 1994

Toxicological & Environmental Chemistry

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The influence of several organic fertilizer treatment regimens, applied at the beginning of crop rotation cycles, were compared as to their slowing down effect on the herbicide diflufenican soil metabolism in wheat crops. In a first trial made at the site "Longs Tours", the organic fertilizers treatment schemes had been repeatedly applied in the past since 30 years, according to a 3 years rotation cycle. The following organic fertilizers treatment regimens were compared: treatment (1) no organic fertilizer at all; treatment (2) cow manure; treatment (3) pig slurry + green manure + crop wastes; treatment (4) green manure + crop wastes; treatment (5) straw cereal wastes alone. A spring wheat crop was sown and diflufenican was applied, i.e. 1.6 years after the latest external organic fertilizers application. During the 4 first crop months, the difiufenican soil half-lives were 59, 91, 117, 81 and 70 days in the treatments 1, 2, 3, 4 and 5 treated plots, respectively. During the end period of the crop, the effect of the organic fertilizers treatments disappeared, the diflufenican and its metabolites soil concentrations becoming very low and similar in the organic fertilizers treated and untreated control plots. A second trial was made with winter wheat at the site "Les Pompes". The organic fertilizers regimens however had been applied only one time 1.2 years before sowing and diflufenican application. In this trial, the organic fertilizers treatments had no significant influence on diflufenican soil half-life.

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Soil metabolism of the herbicide isoxaben in winter wheat crops

Cited by 12 publications

References 6 publications

Isolation and characterization of efficient isoxaben‐transforming Microbacterium sp strains from four European soils

Isolation and characterization of efficient isoxaben‐transforming Microbacterium sp strains from four European soils

Duration of Broadleaf Weed Control with Isoxaben Using Soil Bioassays

Past organic fertilizer treatments: Influence on the herbicide diflufenican soil metabolism in wheat crops

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