Scientists say they have killed nearly all the disease-carrying mosquitoes on two islands in China using a new method.

That is the good news.

The bad news is that the method may cost a lot of money and not work as well in larger areas.

In the experiment, researchers targeted Asian tiger mosquitoes. The insects have white stripes and can spread dengue fever, Zika and other diseases.

To limit the insects' ability to reproduce, scientists first infected a group of mosquitoes with a kind of virus-fighting bacteria. Then they hit them with a small amount of radiation.

The affected mosquitoes were then released onto two small islands near Guangzhou, China. The area suffers from dengue fever.

The scientists reported that, following the insects' release, the number of female mosquitoes responsible for spreading dengue fever dropped by 83 to 94 percent each year.

That drop is similar to what happens after spraying insecticide or using mosquitoes whose genes have been changed.

At times, the new method worked even better than that. Some weeks, researchers saw no signs of disease-carrying mosquitoes.

Zhiyong Xi is with Michigan State University. He led the research team. Xi said that no other mosquito control method has had that kind of total success.

But to achieve that success, researchers had to introduce lots of new mosquitoes onto the islands – up to 4 million each week, over 18 weeks.

Scott O'Neill of the World Mosquito Program says the number of insects needed to control mosquitoes this way is likely too large for most areas.

Biologist Brian Lovett also had concerns. He is with the University of Maryland, just outside Washington, D.C. Lovett said, "You have to keep doing it."

If the process is not repeated, new mosquitoes come in or grow up to replace those that died. Repeating the process could be very costly, Lovett noted.

Researchers from the experiment say the cost will go down as the technology improves. They estimate the cost will soon be about the same as pest sterilization methods, and less costly than some insecticides.

The team is working on a mosquito-control project in an area about four times larger than the islands they used two years ago. Their findings from that first experiment appeared this month in the journal Nature.

I'm Kelly Jean Kelly.

The Associated Press reported this story. Kelly Jean Kelly adapted it for Learning English. Ashley Thompson was the editor.

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insecticide - n. a chemical substance that is used to kill insects

pest - n. an animal or insect that causes problems for people especially by damaging crops

sterilization - n. way to make something unable to produce young