Permethrin plants

Encapsulated fonofos, a soil insecticide, was developed to coat seeds before they were planted (72). Encapsulation reduces oral toxicity 100-fold and dermal toxicity 10-fold while extending activity of the fonofos. Other encapsulated pesticides available include permethrin and parathion (69). Significantly, all commercial encapsulated pesticides are prepared by interfacial polymeri2ation. 

Many investigations of relevant enzymes in transformation of xenobiotics by aquatic species have shown that the similar enzymes observed in metabolism in soil, plant, and mammals play a role, such as esterases and oxidases [10, 159, 160]. Metabolism of pyrethroids has been most extensively studied in fish for cypermethrin (5) and permethrin (15). Aromatic hydroxylation at the 4 -position of the 3-phenoxybenzyl moiety followed by conjugation with glucuronic acid... 

Plant. Metabolites identified in cotton leaves included /ra/js-hydroxypermethrin, 2 hydroxypermethrin, 4 -hydroxypermethrin, dichlorovinyl acid, dichlorovinyl acid conjugates, hydroxydi-chlorovinyl acid, hydroxydichlorovinyl acid conjugates, phenoxybenzyl alcohol, and phenoxy-benzyl alcohol conjugates. Degradation of permethrin was mainly by ester cleavage and conjugation of the acid and alcohol intermediates (Gaughan and Casida, 1978). 

Gaughan, L.C. and Casida, J.E. Degradation of trans- and cis-permethrin on cotton and bean plants, J. Agric. Food Chem., 26(3) 525-528, 1978. 

Pyrethrins are naturally occurring pesticides derived from chrysanthemum plants. They are active against many insects and mites. Over-the-counter liquid and gel preparations of pyrethrins with piperonyl butoxide are available for the treatment of pediculosis (piperonyl butoxide inhibits the hydrolytic enzymes that metabolize the pyrethrins in the arthropod). A synthetic pyre-throid, permethrin (Elimite), is available by prescription. A lower concentration of permethrin (Nix) is available without prescription. Pyrethrins and permethrin are quite safe. 

Pyrethroids are synthetic esters produced to imitate or improve the activity of biological principles of the pyrethrum plant. They are powerful contact insecticides causing rapid knockdown of treated insects. The pyrethroids are extensively used in controlling insect pests on fruit trees, vegetables, and other field crops in space sprays and contact sprays to kill insects infesting homes, industrial locations, and nonfood processing areas and in protection of warehoused food. These compounds include fenvelerate [51630-58-1], (7), R = Cl flucythrinate [70124-77-5], (1) R = CHF20 allethrin [584-79-2] (8) cyfluthrin [68359-37-5] (9) cypermethrin [52315-07-8] (10) deltamethrin [52918-63-5] (11) permethrin [52645-53-1] (12) and tetramethrin [7696-12-0] (13). 

Bioaccumulatlon of some pesticides (fenitrothion, aminocarb, permethrin) with real or potential application in forestry in Canada has been examined in laboratory experiments using larval rainbow trout and common duckweed. Bioaccumulation of an aromatic hydrocarbon, fluorene, has also been examined since some commercial formulations employ hydrocarbon solvents. Laboratory exposures of fish or plants were carried out by placing the organisms in dilute aqueous solutions of C labelled pesticide or hydrocarbon, and by measuring transfer of radioactivity from water to fish or plants. After transfer of fish or plants to untreated water, loss of radioactivity was measured similarly. These measures allowed calculation of uptake and depuration rate constants which were used to predict residue accumulations under various exposure conditions. Predicted residue accumulations agreed substantially with other predictive equations in the literature and with reported field observations. 

There is virtually no literature describing bioconcentration of organic compounds by wild aquatic macrophytes in spite of the facts that these plants are often the major primary producers in shallow inland waters, and are essential habitat components for both aquatic and terrestrial animals. Lockhart et al. (14) provided a regression equation describing uptake curves for a variety of organic compounds by duckweed (Lemna minor) cultures in laboratory exposures. Predictions from the regression equation agreed quite well with field observations on bioconcentration of permethrin in outdoor ponds (15). 

Comparisons among laboratory and field observations are understandably less readily available for aquatic plants than for fish, but some field work has been done with duckweed. The data from pond studies by Rawn et al. (15) with permethrin allow some... 

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]. 

The quantity and quality of food in the diet on which insects are reared may affect their size and survival capacity. Variegated cutworm larvae fed peppermint leaves were more tolerant of the insecticides carbaryl, acephate, methomyl, and malathion than larvae fed snap bean leaves. Increased tolerance for carbaryl and methomyl was also observed in larvae of the alfalfa looper and cabbage looper when they were fed peppermint plants instead of their favored host plants alfalfa and broccoli. Furthermore, fall armyworm larvae fed corn leaves became less susceptible to the insecticides methomyl, acephate, methamido-phos, diazinon, trichlorfon, monocrotophos, permethrin, and cypermethrin than those fed soybean leaves. Although nutrition may play some role in these cases, it was found that enhanced insecticide tolerance caused by these host plants was mainly due to plant allelochemicals, which induced detoxification enzymes in the insects (Yu, 1986). 

In plants permethrin (34) forms metabolites identical with those formed in mammals except for the nature of the conjugating moieties (Gaughan and Casida, 1978). 

Although much is already known about the metabolic pathways of fenvalerate in mammals, plants, and soils, its fate in insects had not been much investigated. Colorado potato beetle was the test organism of a metabolism study in which about 20 metabolites were separated and characterized. Seven different elution systems, with one- or two-dimensional TLC or several developments in the same direction using the same mobile phase, were applied to the separation of the metabolites. Some of them are listed in Table 9 (122). Degradation of cis- and rruns-permethrin in flooded soil was studied using carbonyl- C-cis-, carbonyl- C-trans-, and methylene- C-cis-permethrin. The TLC analysis (123) (Table 9) of soil and water extracts showed a faster degradation of tra/ts-permethrin than of CIS-derivative. 

Pyrethroids are synthetic analogs of derivatives of chrysanthemic acid, 25.6, naturally occurring in plants of the Chrysanthemum genus. The naturally extracted materials, pyrethrin I and II (25.7, 25.8), have been modified for better activity in compounds such as permethrin, 25.9, and deltamethrin, 25.10. They are toxic to cats and to aquatic life but have otherwise generally low toxicity to mammals and are broken down rapidly in the environment. They are widely used as domestic insecticides. You should note that although a single stereoisomer... 

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