Date of Award

1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

Abstract

Fenvalerate, and cis- and trans-permethrin were hydrolyzed by eggs, larvae, pupae, and adults of P. includens and H. virescens. Hydrolysis (per larva) increased logarithmically to a maximum in last instars for the three pyrethroids in both insect species. trans-Permethrin hydrolysis was maximal in midguts, fat bodies, and cuticles of last instar P. includens in the late feeding stage. Changes in rates of hydrolysis appeared to influence toxicity. The midgut of both P. includens and H. virescens was generally the most active tissue in hydrolyzing the three pyrethroids tested. trans-Permethrin was generally hydrolyzed more rapidly than cis-permethrin or fenvalerate. cis- and trans-Permethrin were apparently hydrolyzed by the same enzyme from P. includens midguts, which had a molecular weight of ca. 80,000, a pI of 4.6-4.8, and a Km of 60 (mu)M. The enzyme was susceptible to inhibition by organophosphates, carbamates, chelators, and sulfhydryl groups reagents, and was closer in properties to leucine aminopeptidase than to alpha-naphthyl acetate esterase. Fenvalerate was hydrolyzed by at least four enzymes, with molecular weights of ca. 60,000, and pIs ranging from 4.6 to 6.8. The best organophosphate, chelating, and trifluoropropanone sulfide inhibitors of trans-permethrin hydrolysis in P. includens midguts were relatively nonpolar. Some significant synergism of trans-permethrin to P. includens was seen for compounds in these groups. Field collected H. virescens and P. includens generally hydrolyzed cis- and trans-permethrin and fenvalerate more rapidly than a lab strain. Feeding the lab strain on cotton or tobacco vs. artificial diet generally caused higher rates of hydrolysis in H. virescens, as did feeding the lab strain of P. includens on a resistant variety of soybeans. A strain of H. virescens from California (Imperial Valley) was more tolerant to trans-permethrin (12.5 X), cis-permethrin (5.4 X), and fenvalerate (2.5 X) than a lab strain, but trans-permethrin was equally toxic to both strains when synergized with profenofos. The rates of cis- and trans-permethrin hydrolysis were generally 2-3 X greater in third and last instars of the Imperial Valley than in the lab strain. Isoelectric focusing indicated increased levels and forms of enzyme activity in the Imperial Valley vs. lab strain.

Pages

383

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