If you happen to see a slim fellow slipping into the backyard of a vacant home in your neighborhood, hold off before calling the police.

If you happen to see a slim fellow slipping into the backyard of a vacant home in your neighborhood, hold off before calling the police.

Chances are it's Eugene Papineau, manager of Jackson County Vector Control, in search of "green" swimming pools that are likely swimming with mosquito larvae. Papineau was issued a blanket warrant on Thursday by Jackson County Circuit Court Judge Phil Arnold to enter onto private land in the county in his pursuit of the disease-carrying insects.

"The warrant gives me the authority to go onto property to check swimming pools found to be green and are potential breeding areas for mosquitoes," Papineau explained.

"If I have to, I can cut locks off gates if the place is abandoned and no one is around.

"The warrant is a real help because our work needs to be done immediately, not in a few weeks," he added. "One pool can create millions of mosquitoes that go throughout the entire neighborhood. This is a public-health issue."

The need for the warrant, which is valid through Oct. 31, was prompted by the district's use of an aerial photography program to find homes with mosquito-breeding pools. Using aerial photographs and a blanket warrant to find problem pools are firsts for Oregon, he said.

Photographs taken during the last week in June over Medford, Central Point, White City and Eagle Point revealed 430 swimming pools that were either green, half-empty and green, murky or questionable. Of those, 172 were green pools while 123 were half-empty green pools.

In comparison, the district checked out only 75 pools last year, the result of calls from concerned neighbors.

Pools that are chlorinated stand out as brilliant blue in color photographs. Green pools, tinted by algae, are prime breeding areas for mosquitoes, which can carry diseases such as the West Nile virus.

The photographs were taken by Aerial Services of Castro Valley, Calif., which specializes in low-altitude photography of residential neighborhoods. Several vector control districts in California have used the service to better identify pools that are breeding mosquitoes, Papineau said.

There are plenty of reasons pools aren't being cleaned. Pumps break. Pool chemicals are expensive. People get older and don't want to spend the time or money.

Home foreclosures also are likely to be a contributing factor, Papineau said.

"I've done pools in the past when people call up and say there has been a foreclosure next to their home and they are worried about the mosquito problem from the pool," he said.

His research shows there are about 1,600 mortgage foreclosures in the county. Some of them may have pools that are no longer used, he noted.

"There is no law that requires people to keep their pools clean," he said, although noting a green pool can be a public health risk.

Papineau, who began working for the district in 1978, and has served as the manager since 1986, prefers to work with people rather than employ the warrant.

"If the owners are home, I don't usually have much of a problem," he said, noting the owners are normally very supportive of mosquito control. "But there are some places that are abandoned for foreclosure or whatever. They may have locked gates and are owned by banks in places like Columbus, Ohio, or Virginia."

Vector district employees treat each breeding area with a floating device that releases a bacteria which, when eaten by the mosquito larvae, kills the larvae. If the water source is a pond or other area regularly used by wildlife for drinking, they employ a short-lived chemical that alters the surface tension of the water, causing the larvae to sink and drown.

One pool he treated last week adjacent to a golf course was full of mosquito larvae. There also was a dead squirrel, which apparently drowned in the pool.

"That was a foreclosure," he said. "It doesn't seem to make any difference whether it is the lower-income section of town or a wealthy section. Pools turn green if they aren't cleaned.

"If someone hasn't chlorinated their pool yet, they should do it now," he added. "Otherwise, mosquitoes will find it."

If that happens, chances are Papineau won't be far behind.

Reach reporter Paul Fattig at 776-4496 or e-mail him at pfattig@mailtribune.com.