Pyrethroid Susceptibility in Methyl Parathion-Resistant Tobacco Budworm in South Carolina12

Abstract
High, stable methyl parathion resistance was found in Heliothis virescens (F.) from cotton in South Carolina; larvae were 260-fold resistant to Florence and 188-fold resistant to Bennettsville in 1978 as compared with a Florence strain collected in 1970. Cross-tolerance was 2- to 6-fold to sulprofos and 14-fold to profenofos. Cross-tolerance to permethrin was ca. 10-fold in 1978; however, it declined to 5.6-fold in 1979 and 3.5-fold in 1980 under practical use of pyrethroids in cotton fields. Fenvalerate susceptibility also increased from 1978 to 1980. Median lethal doses in the resistant Florence strain for the experimental pyrethroids AC 222705 and cypermethrin were 1.54 and 2.40 μg/g, respectively.

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