Pearl Rock is a volcanically acidic lava that is sharply cooled by glass ylia and is often used as a building insulation or potted soil additive. However, according to a new study, it is also effective in killing malaria-carrying mosquitoes. At present, people in malaria-prone areas often spray insecticides on surfaces such as mosquito nets around beds. While doing so does kill many of the mosquitoes that fall on these surfaces, pesticides are toxic to people themselves and the environment.
Scientists from North Carolina State University and the Liverpool School of Tropical Medicine recently experimented with a product called Imergard moisture powder in search of a greener alternative. Manufactured by California-based Imerys Alone Minerals, the product is a spray consisting mainly of water and powder pearl rock.
The test was conducted on four groups of cottages in the Republic of Benin, West Africa. The researchers sprayed Imergard on the walls of one group of huts, another with a common insecticide (dewormed chrysanthemums) on the walls of another group, and a combination of the two on the walls of the third group. The fourth group of huts, as a contrast, were not sprayed at all.
As a result, the researchers found that the walls treated with Imegard — whether used alone or in combination with insecticides — initially killed the largest number of malaria-carrying Gambian mosquitoes. But six months after use, the mosquito death rate on the walls of only Imegard was still as high as 78%. By contrast, the mosquito mortality rate on the walls of insecticide-only uses fell to 25 percent over the same period.
The researchers believe that pearl rock particles act as a force attached to insects, destroying the protective lipid layer on its outer cortex. This can lead to the eventual dehydration of mosquitoes and death. In addition, the spray is non-toxic to mammals and is relatively inexpensive, and mosquitoes clearly do not become resistant to it.
“It’s novel to process pearl rock into pesticides,” said David Stewart, co-author of the study and a commercial development manager at Imerys. “This material is not a solution with extreme effectiveness, but a new tool that can be considered as part of a pest management plan. “
The paper was published this week in the journal Insects.