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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 4/1/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Historically, insecticide resistance detection has been accomplished by insecticide bioassay. This method is labor intensive and incapable of detecting resistance frequencies below 10%. An alternative to bioassay is detection of metabolic resistance through quantification of detoxication enzyme activities toward surrogate substrates. For example, naphthyl esters have long been used to identify hydrolytic detoxication mechanisms in mosquitoes, aphids and similar small bodied insects. Although enhanced metabolism is a major mechanism of insecticide resistance in German cockroaches, the relationship between insecticide resistance level and detoxication enzyme activity toward surrogate substrates has not been explored. Therefore, oxidative, hydrolytic, and conjugative detoxication enzyme activities were measured in 10 German cockroach strains collected recently from the field and exhibiting a range of resistance levels to several pyrethroid insecticides in an attempt to identify relationships that could be exploited for the purpose of detecting insecticide resistance. Resistance levels at the LD50 value varied from 3- to >200- fold in topical bioassays compared with the Orlando susceptible strain. No direct relationship was noted between cypermethrin resistance level (or LD50 value) and cytochrome P450 content aldrin epoxidase, methoxyresorufin O-demethylase, or glutathione S-transferase activity. General esterase (toward the substrate pNPA) did result in a moderately good relationship with pyrethroid resistance (cypermethrin). Perhaps with the exception of general esterase, these results indicate that surrogate substrates provide a poor indication for the presence of metabolic pyrethroid resistance in the German cockroach. |
