A low-tech mosquito trap might help control the mosquitoes that spread Zika virus, as well as other viruses such as dengue and chikungunya, government researchers said Tuesday.

The traps cut in half the number of cases of chikungunya when they were used in a few neighborhoods in Puerto Rico over the winter, a team at Puerto Rico’s health department and the Centers for Disease Control and Prevention said.

“We think if it’s effective against chikungunya virus transmission, then it should be effective against transmission of other pathogens, such as dengue and Zika viruses,” said Tyler Sharp, an epidemiologist at the CDC’s dengue branch in Puerto Rico.

The trap uses no pesticides or chemical attractants. The mosquitoes can develop resistance to insecticides and have done so in parts of Puerto Rico.

“It’s about the size of a five-gallon bucket,” Sharp said. “It’s basically water, hay and glue.”

Mosquito traps are nothing new — but this one is particularly effective and inexpensive, the CDC team said.

“It’s very important that the bucket is black,” Sharp said. “That’s the color that the mosquitoes are attracted to.”

The water-soaked hay attracts female mosquitoes and the sides of the bucket are coated with glue. When the female mosquitos land to rest before laying their eggs in the smelly water, they get stuck.

The CDC-led team tested the traps in several Puerto Rican communities, they report in a special release of the CDC’s reports on death and disease.

In the communities where there were not traps, 45 percent of the 152 people tested had been infected with chikungunya, the researchers reported. Only 23 percent of the 175 people living in the communities with traps had been infected.

The CDC has licensed the trap technology to Washington state based Spring Star Inc. to make on a large scale, Sharp said.

Although they sound simple, the traps cannot just be made at home, Sharp cautioned.

“How you put it together is very important,” he said. “You cannot just grab a bucket, throw some glue in it and it’ll work.”

For one thing, the wrong type of glue will repel the mosquitoes, he said. And if it’s not designed just right, it could actually act as an incubator for the mosquitoes.

“It is important to note that these traps are not going to solve the Zika outbreak or any future outbreak,” Sharp added.

“They are one tool of many that can be utilized to reduce an individual’s risk of infection with any of these viruses that are transmitted by Aedes aegypti mosquitoes.

They have to be used intensively to work well, Sharp said. “In these communities that have traps … there are three traps per home in about 85 percent of the homes,” he said.

But it might be possible to cluster them in and around the homes of pregnant women in Zika-affected areas, Sharp said.

Zika’s spread across much of central and South America and the Caribbean since late last year. It’s infected hundreds of thousands of people and is now known to cause severe birth defects when it infects pregnant women.

It is almost certain that it can also cause neurological damage, such as the paralyzing Guillain-Barre syndrome. While Zika is rarely deadly, it killed a man in Puerto Rico earlier this year.

There’s no vaccine yet and no specific treatment and the World Health Organization and CDC say the best way to fight it is to get rid of the mosquitoes that spread it. They’re trying a range of options, from insecticides to genetically engineered mosquitoes, mosquitoes infected with bacteria that stop the virus and old-fashioned control of standing water.