Indoor volcanic-glass spray may be promising new weapon for mosquito control

9 Jun 2020

Image: © panyawat/

Researchers have found that a spray containing volcanic glass shows serious promise for controlling mosquitoes indoors.

With malaria remaining one of the greatest health risks across the globe – killing approximately 400,000 people in Africa alone each year – efforts continue to find the most effective repellent for the mosquitoes that spread the disease. However, mosquitoes are becoming increasingly resistant to the commonly used insecticides such as pyrethroids, requiring the development of new innovations.

Now, researchers from North Carolina University have revealed an indoor spray made by combining volcanic glass with water, which shows serious promise in controlling disease-carrying mosquito populations.

Writing in the journal Insects, they said the volcanic glass used in the spray is perlite, most commonly used in building materials and in gardens as a soil additive. This new insecticide, combined with water, has been dubbed Imergard WP and can be applied to interior walls and ceilings – and perhaps even inside roofs – as an indoor residual spray.

No additional chemicals are needed, so the spray is non-toxic to mammals. More importantly, a recent study has shown that mosquitoes appear to have no resistance to it. The researchers used four different tests to verify the efficacy of Imergard WP.

‘Many die within a few hours of contact’

The control study had no mosquito-prevention spray, the second group had walls of a hut coated with a common pyrethroid, a third group saw hut walls sprayed with Imergard WP, and a fourth group sprayed a mixture of Imergard WP and pyrethroid on walls.

The huts treated with the volcanic-glass spray, with and without pyrethroid, showed the largest mosquito mortality rates. Results showed mortality rates of mosquitoes alighting on Imergard WP-treated walls were greater than 80pc up to five months after treatments, and 78pc at six months.

Mike Roe, corresponding author of the paper, said: “The statically transferred perlite particles essentially dehydrate the mosquito.

“Many die within a few hours of contact with the treated surface. Mosquitoes are not repelled from a treated surface because there is no olfactory mechanism to smell rock.”

By comparison, huts sprayed with the common pesticide had mosquito mortality rates of between 40pc and 45pc over five months, falling to 25pc within six months.

David Stewart, co-author of the paper, added: “This material is not a silver bullet but a new tool that can be considered as part of an insect vector management programme.”

Colm Gorey was a senior journalist with Silicon Republic