Bioassay and biochemical studies of the status of pirimiphos-methyl and cypermethrin resistance in Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Singapore.

Aedes (Stegomyia) aegypti (Linnaeus) and Ae. (Stegomyia) albopictus (Skuse) were sampled from five regions of Singapore (Central, North East, North West, South East and South West) and tested with diagnostic concentrations of the technical grade insecticides, pirimiphos-methyl and cypermethrin. Biochemical assays were performed on the same populations of Ae. aegypti and Ae. albopictus to determine activities of detoxifying enzymes, including non-specific esterase (EST), monooxygenase (MFO) and acetylcholinesterase (AChE). The diagnostic test showed that all Ae. aegypti populations were susceptible to pirimiphos-methyl (mortality = 99 to 100%), but resistant to cypermethrin (mortality = 11 to 76%). Resistance to pirimiphos-methyl was observed in all Ae. albopictus populations (mortality = 49 to 74%) while cypermethrin resistance was detected in most Ae. albopictus populations (mortality = 40 to 75%), except those from Central (mortality = 86%) and South East (mortality = 94%) showing incipient resistance. The biochemical assays showed that there was significant enhancement (P < 0.001) of MFO activity in pyrethroid-resistant Ae. albopictus populations and most Ae. aegypti populations. The biochemical assay results suggested that AChE could play a role in pirimiphos-methyl resistance of Ae. albopictus in South West, South East and North East regions. The small but significant increase in EST activities in Ae. aegypti from all regions suggest that it may play a role in the observed cypermethrin resistance.

Bioassay and biochemical studies of the status of pirimiphos-methyl and cypermethrin resistance in Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Singapore Singapore 138667

Aedes (Stegomyia) aegypti (Linnaeus) and Ae. (Stegomyia) albopictus (Skuse) were sampled from five regions of Singapore (Central, North East, North West, South East and South West) and tested with diagnostic concentrations of the technical grade insecticides, pirimiphos-methyl and cypermethrin. Biochemical assays were performed on the same populations of Ae. aegypti and Ae. albopictus to determine activities of detoxifying enzymes, including non-specific esterase (EST), monooxygenase (MFO) and acetylcholinesterase (AChE). The diagnostic test showed that all Ae. aegypti populations were susceptible to pirimiphos-methyl (mortality = 99 to 100%), but resistant to cypermethrin (mortality = 11 to 76%). Resistance to pirimiphos-methyl was observed in all Ae. albopictus populations (mortality = 49 to 74%) while cypermethrin resistance was detected in most Ae. albopictus populations (mortality = 40 to 75%), except those from Central (mortality = 86%) and South East (mortality = 94%) showing incipient resistance. The biochemical assays showed that there was significant enhancement (P < 0.001) of MFO activity in pyrethroid-resistant Ae. albopictus populations and most Ae. aegypti populations. The biochemical assay results suggested that AChE could play a role in pirimiphos-methyl resistance of Ae. albopictus in South West, South East and North East regions. The small but significant increase in EST activities in Ae. aegypti from all regions suggest that it may play a role in the observed cypermethrin resistance.

New mosquito species records (Diptera: Culicidae) from Singapore.

Nine species of mosquitoes in eight genera are recorded for the first time in Singapore. An additional two species were overlooked in a 1986 checklist for mosquitoes in Singapore, and one was described after 1986. Location and habitat data are provided for the nine new records. With the inclusion of these new records the number of species reported from Singapore is 137.