Aerobic and anaerobic soil metabolism of dicamba

Sorption of aged dicamba residues in soil

“…Several investigators have reported that dicamba, a weak acid herbicide (pK a , 1.95),20 dissipated rapidly from soil with half‐lives ranging from days, under favorable conditions, to weeks 21–24. Metabolism by soil micro‐organisms would appear to be the major pathway of dicamba degradation under most soil conditions 21, 22, 25.…”

“…Several investigators have reported that dicamba, a weak acid herbicide (pK a , 1.95),20 dissipated rapidly from soil with half‐lives ranging from days, under favorable conditions, to weeks 21–24. Metabolism by soil micro‐organisms would appear to be the major pathway of dicamba degradation under most soil conditions 21, 22, 25. Dicamba is completely mineralized or is biologically transformed to other compounds, including 3,6‐dichlorosalicylic acid (3,6‐DCSA) (pK a , 1.95)20 by demethylation and this, in turn, can be hydroxylated to give 2,5‐dihydroxy‐3,6‐dichlorobenzoic acid (2,5‐diOH) metabolite,21 both of which may become reversibly or irreversibly bound to soil, competing with dicamba for possible sorption sites 21, 26…”

A Three-component Dicamba O-Demethylase from Pseudomonas maltophilia, Strain DI-6

“…Like a number of other chlorinated organic compounds, dicamba does not persist in the soil because it is efficiently metabolized by a consortium of soil bacteria under both aerobic and anaerobic conditions (1)(2)(3)(4). Studies with different soil types treated with dicamba have demonstrated that 3,6-dichlorosalicylic acid (DCSA), 1 a compound without herbicidal activity, is a major product of the microbial degradation process (2,3,5). Soil samples taken from a single site exposed to dicamba for several years yielded a number of bacterial species capable of utilizing dicamba as a sole carbon source (6).…”

Use of Field Lysimeters To Determine 14C-Dicamba Persistence and Movement in Soil

“…Metabolites monitored are often dependent on the ease of analysis Because of dicamba's (3,6-dichloro-2-methoxybenzoic acid) low sorption in soils at normal pH levels (1)(2)(3), it is a potentially highly mobile herbicide (4)(5)(6). However, mitigating the sorption effects on mobility is the fact that dicamba can be rapidly degraded (7)(8)(9). Degradation products include 3,6-dichloro-2-hydroxybenzoic acid (3,6-DCSA), 3,6-dichloro-5-hydroxy-2-methoxybenzoic acid (5-HO-dicamba), 3,6-dichloro2,5-dihydroxybenzoic acid (2,, and C0 2 (10).…”