Degradation of Several Herbicides in a Soil Previously Treated With McPa

Abstract

Summary. Soil which had received nine previous field treatments of MGPA (33 kg/ha) at intervals of about 6 months, and which had become able to detoxify MCPA more rapidly than untreated control soil, was able to degrade MCPB with equal facility. In contrast, the disappearance rates of phytotoxic residues of dichlorprop (2‐(2,4‐dichloro‐phenoxy)propionic acid), mecoprop (2‐(4‐chloro‐2‐methylphenoxy)propionic acid), fenoprop (2‐(2,4,5‐trichlorophcnoxy)propionic acid) and dicamba (2‐methoxy‐3,6‐dichlorobcnzoic acid), as determined with a bioassay technique, were unaffected by previous treatments of the soil with MCPA. Indirect evidence from these studies suggests that β‐oxidation of MCPB to MCPA did not occur to any significant extent either in the soil to which the roots of the indicator plant were exposed or in the roots themselves. Dégradation de quelques herbicides dans un sol préddenvnent traté avec le MCPA Résumé. Un sol ayant reçu 9 traitements au MGPA (3,3 kg/ha) à des intervalles d'environ 6 mois et qui est devenu capable de dégrader le MCPA plus rapidement qu'un téntoin non traité, s'est montré capable de diégrader le MGPB avec la mêmefacilité. En revanehe, les taux de disparition de résidus toxiques déterminés par des testsbiologiques, du dichlorprop (acide 2‐(2,4‐dichlorophenoxy)propionique), du mécoprop(acide 2‐(4‐chloro‐2‐méthylphénoxy)propionique), du fénoprop (acide 2‐(2,4,5‐trichlorophénoxy)propionique) et du dicamba (acide 2‐méthoxy‐3,6‐dichlorobenzoique) n'ont pas été affectés par les traitements antérieurs avec le MCPA. Comme conclusion indirecte de ces travaux il est suggéré que la β‐oxydation du MGPB en MCPA ne se produit pas à un dcgré significatif dans le sol où les racines desplantes servant d'indicateurs sont plongées, pas plus que dans les racincs elles‐mêmes. Abbau von verschiedenen Herbiziden in einem vorher mit MCPA behandelten Boden Zusammenfassung. Boden, der auf dem Feld in Abstanden von sechs Monaten neunmal mit MGPA (3,3 kg/ha) behandelt wurde und dadurch in der Lage war, MGPA schneiler umzuwandeln als der unbchandelte Kon troll boden, konnte MCPB gleichermassen abbauen. Mit Hilfe von Biotests wurde ermittelt, dass vorausgehende Behandlungen des Bodens mit MCPA dagegen keinen Einfiuss auf die Abbaurate phytotoxischer Rückstände von Dichlorprop (2‐(2,4‐Dichlor‐phenoxy)‐propionsäurc), Mecoprop(2‐(4‐Ghlor‐2‐methyl‐phenoxy)‐propionsäure), Fenoprop (2‐(2,4,5‐Trichlorphenoxy)‐propionsaure) und Dicamba (3,6‐Dichlor‐2‐methoxy‐benzoesaure) hatten. Die Ergebnisse lassen darauf schliessen, dass der β‐Oxidation von MCPB zu MGPA weder im Boden, dem die Wurzein der Testpflanzen ausgesetzt waren, noch in den Wurzeln selbst Bedeutung zukam.

Characterisation of bacterial cultures enriched on the chlorophenoxyalkanoic acid herbicides 4-(2,4-dichlorophenoxy) butyric acid and 4-(4-chloro-2-methylphenoxy) butyric acid

“…However, it is not known whether this process is microbially mediated. Conversion of MCPB to MCPA in soils by a similar mechanism has not previously been recorded, although some studies have unsuccessfully tried to establish the presence of MCPA in MCPB-treated soils [10]. Our results show the production of 2,4-DCP and MCP during degradation by cultures containing 2,4-DB and MCPB, respectively, as carbon sources.…”

Enhanced degradation and the comparative fate of carbamate insecticides in soil

“…Chapman et al (1986b) determined that although one laboratory pretreatment of soil with carbofuran induced rapid degradation of both carbofuran and carbaryl, four pretreatments were needed to induce rapid cloethocarb degradation and oxamyl was not rapidly degraded even after nine carbofuran pretreatments. A range of selectivity of cross-adaptions involved in enhanced degradation has also been reported within the phenoxyacetic acid herbicide class (Kirkland and Fryer, 1972) and the thiocarbamate herbicide class (Wilson, 1984;Skipper et al, 1986;Harvey et al, 1986).…”

“…Pesticide catabolism by adapted soil microorganisms is microbially beneficial in that the pesticide or a hydrolysis product serves as a microbial carbon, energy, or nutrient source (Fournier et al, 1981;Karns et al, 1986;Racke and Coats, 1987;Tam et al, 1987). Enhanced degradation has been reported for a number of insecticides (Sethunathan and Pathak, 1972;Felsot et al, 1981;Read, 1983Read, ,1987Racke and Coats, 19871, herbicides (Newman and Thomas, 1949;Audus, 1951;Kirkland and Fryer, 1972;Wilson, 1984;Gray and Joo, 1985;Skipper et al, 1986), and fungicides (Walker et al, 1986;Yarden et al, 1986).…”

Comparative degradation of organophosphorus insecticides in soil: specificity of enhanced microbial degradation

“…This has 1980). The ephemeral nature of terbufos and phorate in soil has been well documented (Getzin and Chapman, 1960;Suett, 1975;Sellers, et al, 1976;Chapman et al, 1982a,b), and it is terbufos sulfoxide and phorate sulfone that are been true to some extent with the carbamate insecticides (Harris et al, 1984;Felsot, 1986), thiocarbamate herbicides ( Wilson, 1984; Harvey et al, 1986), and phenoxyacetic acid herbicides (Kirkland and Fryer, 1972). However, the enhanced degradation of organophosphorus insecticides in soil has usually been associated with a lesser degree of crow adaptation.…”