Abstract
Resistance to malathion in Anopheles stephensi from Pakistan was measured at intervals during the first week of adult life. LT50 values for homozygous resistant females decreased four-fold during the first 7 days of adulthood. A decrease in resistance with age also occurred in heterozygotes; the LT50 values of males and females fell sevenfold during the first 5 days of adulthood. The sensitivity to malathion of a susceptible strain increased with age. A biochemical basis for the declining resistance levels was investigated. Resistant and susceptible adults were homogenized at intervals during the first week of adulthood and soluble extracts were incubated with [14C]malathion. The rate of malathion metabolism to mono- and dicarboxylic acids was faster in resistant than in susceptible mosquitoes. The rate of malathion metabolism decreased with age in both strains. A decrease in carboxylesterase activity with age in resistant and susceptible mosquitoes is thus responsible for the increasing sensitivity to malathion. Implications for the monitoring of resistance in the field by diagnostic dosages and for the future use of malathion in mosquito control are discussed.
| Original language | English |
|---|---|
| Pages (from-to) | 239-247 |
| Number of pages | 9 |
| Journal | Pesticide Biochemistry and Physiology |
| Volume | 28 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 1 Jun 1987 |
| Externally published | Yes |