- Biological Activity of Pyrethroid Analogs in Pyrethroid-Susceptible and -Resistant Tobacco Budworms, Heliothis virescens (F.)
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The phenoxybenzyl moiety of conventional pyrethroids is a major site of oxidative metabolism in resistant tobacco budworms, Heliothis virescens (F.). In this study, this group was replaced with known P450 monooxygenase-inhibiting or oxidatively blocked groups. A variety of isomers (1R/1S, cis/trans) of the resulting chrysanthemates were tested as insecticides or synergists against tobacco budworms that were insecticide-susceptible (LSU) or that expressed metabolic resistance to cypermethrin (Pyr-R). A number of compounds with pentafluorophenyl, methylenedioxyphenyl, and propargyloxyphenyl groups were insecticidal, and activity was dependent on both geometric and stereochemical configuration of the acid moiety. Both trans and cis isomers of 1(R)-fenfluthrin, which contains a pentafluorophenyl group, suppressed resistance to cypermethrin in Pyr-R insects, confirming that oxidative metabolism of the phenoxybenzyl moiety is a major mechanism of resistance in this strain. Of the methylenedioxyphenyl compounds, 1R, trans, and cis isomers were toxic and partially suppressed resistance in Pyr-R larvae. Similarly, both trans and cis isomers of α(S),1(R)-propargyloxyphenyl-containing compounds were insecticidal. Finally, α(R),1(R)-cis-methylenedioxyphenyl- and -propargyloxyphenyl- containing compounds were nontoxic but significantly enhanced toxicity of cypermethrin.
- Shan, Guomin,Hammer, Robert P.,Ottea, James A.
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p. 4466 - 4473
(2007/10/03)
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- Synergism by propynyl aryl ethers in permethrin-resistant tobacco budworm larvae, heliothis virescens
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Synergists were used to diagnose possible mechanisms of permethrin resistance in permethrin-selected strains of the tobacco budworm, Heliothis tirescens (F.). In addition to permethrin, these strains of the tobacco budworm were resistant to a-cyano-pyrethroid insecticides, organophosphorus insecticides and DDT. The monooxygenase-inhibiting prop-2-ynyl aryl ethers were the only effective synergists of permethrin among 16 candidates tested. The most effective synergist was l,2,4-trichloro-3-(2-propynyloxy)benzene. Piperonyl butoxide, a common monooxygenase-inhibiting synergist in other species and tobacco budworm strains, was inactive. These results suggested the presence and contribution of an unusual monooxygenase in the enzymatic detoxication of permethrin. DDT cross-resistance, which was not synergized, and broad pyrethroid cross-resistance supported previous evidence for target site insensitivity as a second pyrethroid-resistance mechanism in these strains. The actions of S,S,Stributyl phosphorotrithioate (TBPT) and triphenyl phosphate (TPP) suggested that hydrolytic detoxication, important in methyl parathion-resistance tobacco budworm strains, had little or no role in conferring pyrethroid resistance in these strains.
- Brown, Thomas M.
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p. 323 - 331
(2007/10/03)
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