Nora Atondo, a sanitarian assistant with the Pima County Health Department, searches for mosquito larvae in 2-week-old standing water in front of University Physicians Healthcare Hospital at Kino Campus. A UA College of Agriculture entomologist is looking at treatments for standing water like this.

Photos by David Sanders / arizona daily star

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That mosquito that bit you isn't carrying West Nile... yet

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The post-monsoon squadrons of mosquitoes attacking your ankles are just extremely annoying, not deadly. You'll have to wait a bit longer for that.

The current swarms of highly aggressive mosquitoes — often referred to as "ankle-biters" — are "incompetent vector mosquitoes," says Patti Woodcock, Pima County Health Department spokeswoman.

They don't carry West Nile virus, at least not here.

Woodcock said that although the ankle-biters are shooting blanks in Southern Arizona, they sometimes carry deadly diseases elsewhere. She doesn't know why.

But as we ponder that bit of good luck, Woodcock and other mosquito-program officials and experts expect that the two Culex mosquito varieties that do carry West Nile virus may be breeding like fiends.

Typically, local and state officials say, West Nile doesn't start to show up until late August or into September. Last year there were three West Nile deaths in Pima County. There were 143 confirmed human cases of West Nile virus in the state and 46 in Pima County in 2006.

To date, Woodcock said, Pima County has had only one dead bird — a thrush found near East Prince and North Country Club roads — test positive for West Nile virus. No humans have tested positive.

It may take the mosquitoes carrying West Nile virus longer to build up a population, said University of Arizona entomologist Elizabeth Willott.

She said the ankle-biters can go from egg to pupal stage in six days, but the Culex mosquitoes take a week or more.

"That might be all it takes," Willott said, "but that's just speculation."

Then again, she wonders whether the delay in their emergence might be from the streaks of high temperatures, which may make the breeding water too hot.

The message in all the uncertainty, Woodcock said, is that we're far from over the hump.

Not everyone has been lucky. Craig Levy, an Arizona Department of Health Services epidemiologist, said 18 people in Maricopa County and one person in Pinal County have tested positive for West Nile virus.

"When it does show up," Levy said, "it sometimes shows up with a vengeance."

But Levy isn't jumping to conclusions. He, too, says there are many things that aren't understood about mosquitoes and how they spread disease.

And some of what is known, Levy said, is counterintuitive.

For instance, he said heavy rains can actually slow the mosquito population's growth.

"Rains flush out storm drains, (but) then they start breeding successfully again," Levy said.

And although positive cases popped up earlier than usual, at least in other parts of the state, Levy said reports have been tapering off.

"This year, we don't know what to expect," Levy said.

City and county crews are aggressively treating standing water, Woodcock said, and public-education efforts are going strong.

One of the education efforts is the Midtown Mosquito Pilot Project, being run out of the Tucson Botanical Gardens on North Alvernon Way near East Grant Road.

UA entomologists are monitoring mosquito traps there, and project workers have gone through the adjacent neighborhood knocking on doors and passing out information.

"There's a real misconception in the public that plants are breeding mosquitoes," said Nancy Laney, the gardens' executive director.

Aside from saucers that may collect overflow from flowerpots, Laney said plants are not a problem.

"Plants can often help with mosquito problems because they help water infiltrate (into the ground). It's not producing mosquitoes."

Laney said she became aware of the misconception while listening to audience members at a public meeting.

"Someone said, 'I've completely bladed my whole yard, and I'm still having (mosquito) problems,' " Laney said.

"We don't want people to think they've got to have a bare yard to get rid of mosquitoes."

The most common problem program workers have seen while visiting the gardens' neighbors is from plastic kiddie pools and toys left in backyards collecting water — particularly those left behind walls where they are out of sight and forgotten, Laney said.

Meanwhile, a UA College of Agriculture entomologist is evaluating treatments for standing water.

There are products that work to varying degrees to inhibit growth of mosquitoes in standing water, said Tim Dennehy.

"Mosquito dunks work marvelously," Dennehy said.

But the doughnut-shaped pellets plopped in water to kill larvae typically inhibit mosquitoes only before their later stages.

Dennehy said the test results are just preliminary and won't be published until next year.

So far, he said, vegetable oils advertised for treating standing water don't seem to work.

But some petroleum-based oils are effective.

Bleach was not found to be effective. Common rumored fixes, such as apple cider vinegar and hydrogen peroxide, don't seem to work.

But he said one "folk cure" that does work surprisingly well is dish-washing soap — at least the two brands they tested: Sunlight Ultra Lemon Citrus Burst and Trader Joe's Seventh Generation brand.

Dennehy said they had not yet worked out the concentrations required, however, and that it had to be a balance between too little and enough to create "a bubble bath."