Summary. A quantitative study was carried out on the absorption, translocation and metabolism of 2,6–dichlorobenzonitriie‐14G (dichlobenil) in seedlings of Phaseolus vulgaris L. From an aqueous solution dichlobenil is absorbed by the roots and accumulates about three‐fold; metabolism in the roots is of minor importance. From the roots the herbicide is translocated throughout the plant. In the leaves two competitive processes take place: the main part (90%) of the dichlobenil evaporates and another part is metabolized. The principal metabolic pathway is hydroxylation, followed by conjugation, 3–hydroxy‐2,6–clichlorobenzonitriIe and 4–hydroxy‐2,6–dichlorobenzonitrile analogues being formed in a ratio of about 4:1. Hydrolysis of dichlobenil into 2.6–dichlorobenzamide and 2,6–dichlorobcnzoic acid is only a minor metabolic route. From a saturated atmosphere dichlobenil is taken up rapidly through the leaves but little translocation occurs to the roots. Following foliage application more of the applied dichlobenil Is metabolized because evaporation of dichiobenil as a competitive process is virtually eliminated. Absorption, migration ei métabolisme du dichlobenil dans les plantules de haricot

Summary. A study was made of the breakdown of 14C‐dichlobenil (2,6‐dichlorobenzonitrile) added at 2 ppm to a sandy soil containing 4% organic matter. After 8 months more than half the added herbicide had been metabolized. The major conversion product was 2,6‐dichlorobenzamide (95% of total metabolites). Three minor metabolites (each about 1%) were found but could not be identified. The hydrolysis to 2,6‐dichlorobenzamide appears to be a microbiological process. The great stability of the major metabolite was confirmed in a separate experiment in which 14C‐2,6‐dichlorobenzamide was added to the soil at 2 ppm. After 6 months about 90% of the added 2,6‐dichlorobenzamide was recovered. Métabolisme du dichlobenil en sol sableux Résumé. La degradation du 14C‐dichlobenil (2,6‐dichlorobenzonitrile), a étéétudiée, à la concentration de 2 ppm, dans un sol sableux contenant 4% de matiére organique. Après huit mois, plus de la moitié de I'herbicide apporté avait été métabolisé. Le plus important des produits de dégradation fut le 2,6‐dichlorobenzamide (95% du total des metabolites). Trois métabolites mineurs, représentant environ 1% chacun furent trouvés mais ne purent étre identifiés. L'hydrolyse à la 2,6‐dichlorobenzamide semble être un processus microbiologique. La grande stabilityé du métabolite principal fut confirmée dans une autre expérience dans laquelle le 14C‐2,6‐dichlorobenzamide fut ajouté au sol à raison de 2 ppm. Après 6 mois, 90% environ du 2,6‐dichlorobenzamide fut retrouve. Abbau von Dichlobenil in Sandboden Zusammenfassung. Es erfolgte eine Untersuchung über den Abbau von 14C‐Dichlobenil (2,6‐Dichlorbenzonitril), dass in einer Konzentration von 2 ppm einem Sandboden mit 4% organischer Substanz zugegeben worden war. Nach 8 Monaten war mehr als die Halfte des zugefügten Herbizids abgebaut. Das wichtigste Abbauprodukt war 2,6‐Dichlorbenzamid (95% der gesamten Abbauprodukte). Drei weniger bedeutende Abbauprodukte (jedes weniger als 1%) wurden gefunden, doch konnten sie nicht identifiziert werden. Die Hydrolyse in 2,6‐Dichlorbenzamid ist offensichtlich ein mikrobiologisch bedingter Vorgang. Die grosse Stabilitat des wichtigsten Metaboliten wurde in einem getrennten Versuch bestatigt, in welchem 14C‐2,6‐Dichlorbenzamid dem Boden in einer Konzentration von 2 ppm zugefuhrt wurde. Nach 6 Monaten wurden ungefahr 90% des zugefügten 2,6‐Dichlorbenzamid wiedergefunden.

SUMMARY2,6‐Dichlorobenzamide (BAM) induced leaf margin chlorosis (LMC) on the leaves of kale seedlings and apple trees when applied to the roots. The leaf symptoms were similar to those sometimes seen after use of the herbicides chlorthiamid and dichlobenil. BAM was deposited mainly in the margin of the leaf to which BAM was transported via the transpiration stream. BAM appeared to be the causative agent of chlorosis although hydroxy derivatives of BAM were also present in the leaf. Factors possibly responsible for the variations in the occurrence and in the intensity of LMC are discussed.

[14C]Diflubenzuron is readily degraded in various agricultural soils and in hydro‐soil; 50% of the applied dose of 1 mg kg−1 was metabolised in 2 days or less. The chief products of hydrolysis were identified as 4‐chlorophenylurea and 2, 6‐difluorobenzoic acid. A part of the radioactivity, increasing with incubation time, could not be extracted. Release from the soil of [14C]carbon dioxide, derived from both labelled phenyl rings, points to the ultimate mineralisation of diflubenzuron.

2,6-Difluorobenzoic acid, one of the two primary dijlubenzuron metabolites, is rapidly and completely degraded in soil. Times to 50 % disappearance were 9 and 12 days in two agricultural soils. [14C]Carbon dioxide was an ultimate product of the ring-14C-labelled compound. A part of the radioactivity, increasing with time to one third of the applied dose of I mg k g -' , could not be extracted ffom the soil.