Bifenthrin nursery

In laboratory microcosms, ira 5-permethrin was selectively degraded compared to the other diastereomer, cw-permethrin, by six bacterial strains [19]. These strains also preferentially biotransformed 15-cw-bifenthrin over their antipodal l/ -cw-enantiomers, which were more toxic to daphnids [19]. Enantioselectivity was more pronounced for cw-permethrin than for cw-bifenthrin, and was strain-dependent. The (—)-enantiomer of both pyrethroids was preferentially depleted in sediments adjacent to a plant nursery, suggesting that in situ microbial biotransformation was enantioselective [20]. Although all enantiomers of permethrin were hydrolyzed quickly in C-labeled experiments in soils and sediments, the degradates of both cis- and irara-permethrin s -enantiomers were mineralized more quickly than those of the 5-enantiomer, while degradation products of cA-permethrin were more persistent than those of the trans-isomex [185]. Enantioslective degradation of fenvalerate in soil slurries has also been reported [83]. These smdies underscore how enantiomer-specific biotransformation can affect pyrethroid environmental residues, the toxicity of which is also enantiomer-dependent [18-20]. 

Since 1998, as a conq>onent of quarantine practices against red and ittq)orted fire ant (RIFA) infestation, all plant containers at this and other nurseries in this region have been required to be treated with bifenftirin (2-methylbiphenyl-3-yl-methyl(Z)-(lRS)-cw-3-(2-chloro-3,3,3-trifluoropropenyl)-2,2-dimethylcyclopropane-carboxylate). The treatment is typically carried out by incorporating a granular bifenthrin formulation, Talstar , into potting mixes... 

Two synthetic pyrethroid insecticides, bifenthrin and permethrin (3-phenoxybenzyl (lR5)-cis-fra s-3-(2,2-dichlorovinyl)-2,2-dimcthylcyclopropane-carboxylate), are the major runoff constituents considered in our monitoring and evaluation studies. Bifenthrin has a solubility of <1 ppb, and a Koc of240,000 ml g. Permedirin has a solubility of 6 ppb in water, and a Ka- of 100,000 ml g (5). The stroi adsorption on soil suggests that a large fiaction of the pesticide is associated wifii die suspended solids in nursery runoff. This determines that the downstream distribution of these pesticides is closely related to distribution of sediments, and that practices aiming to remove suspended solids from runoff will also be effective in reducing the level of these pesticides. 

Table 2. Concentrations of bifenthrin and permethrin found in surface soils collected from a nursery site...

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