There is "no silver bullet" in the fight against dengue, said Minister for the Environment and Water Resources Masagos Zulkifli in Parliament yesterday.

He was addressing a question from Mr Ong Teng Koon, an MP for Marsiling-Yew Tee GRC, on whether fogging is still an effective tool to combat the Aedes aegypti mosquito.

Mr Masagos said that in areas where there has been a higher incidence of dengue fever, 70 per cent of mosquito breeding habitats were found in homes.

"Even if we carry out more fogging, what residents would usually do is close their windows," he said, adding that destroying mosquito habitats, which are mostly found in homes, would be the best way to prevent dengue from spreading.

However, said Mr Masagos, fogging "can and must" be done to kill adult mosquitoes outside of homes.

He also said Project Wolbachia, a scheme involving the release of sterile male mosquitoes leading to eggs that cannot hatch, is not a "silver bullet" to the dengue situation.

While results from field studies have shown promise, the technology has been tested only in small study sites in Singapore and remains under research and development, the minister said.

The project is now in its third phase, which aims to determine if the suppression of the Aedes aegypti population achieved thus far can be sustained in larger areas.

The current release area, which covers 84 Housing Board blocks in Yishun and another 60 blocks in Tampines, is 3.7 times larger than the release area when the project first started.

However, as field studies require prior systematic design, preparation and historical data for comparison, they are not suited for reacting to current dengue clusters, which are very dynamic.

Mr Masagos added that Wolbachia technology will not replace community efforts, comprehensive mosquito surveillance, source eradication of mosquito breeding habitats, and the spraying of insecticide where necessary to control the adult mosquito population.