Scientists are using an agricultural fungus to kill mosquitos that are responsible for more than 300 million cases of malaria and kill approximately three million people each year in tropical and sub-tropical countries. The researchers say the new technique has several advantages over chemical insecticides.

Researchers are testing a new approach to controlling malaria mosquitos to avoid the use of potentially dangerous chemicals.

In two papers published in the June 9 issue of Science, investigators report using fungi against female mosquitos infected with the malaria parasite. Fungi are used in farming to control insect pests.

In one study co-authored by research ecologist Matt Thomas of Imperial College in London, researchers used an American fungus to treat walls and ceilings where mosquitos rest after a blood meal. Professor Thomas says the fungi fill up the insects rapidly.

"They start to become really sick from day seven onwards. Those mosquitos reduce feeding, so they are less likely to take a blood feed and they are less likely to transmit even before they are dead," Mr. Thomas says.

Professor Thomas says the technique takes advantage of the seven to 14 day window between the time an infected mosquito feeds and goes searching again for another meal. In the study, the fungus killed ninety percent of the mosquitos infected with the malaria parasite.

In a second study, investigators report using a fungus that's used to kill locusts. They treated sheets and hung them in 10 huts in rural Tanzania. The experiment resulted in a modest reduction in the number of malaria mosquitos. But scientists calculated the reduction could translate into significantly fewer infectious mosquito bites in humans.

Wendy Gelernter is a consultant on biopesticides and a member of the Society for Invertebrate Pathology.

Ms. Gelernter says the researchers will have to overcome a number of obstacles before fungi can be used against malaria mosquitos.

"They're going to have to determine how long this fungus is going to actually survive in a hot, humid environment. And hopefully it will survive a long time so it doesn't have to be reapplied too many times," Ms. Gelernter says. "But they've made the first important step in proving it can be done; it's technically feasible"

Ms. Gelernter says the biggest challenge will be finding someone to pay for more extensive studies.