District takes battle against mosquitoes to the street

Night was falling as the five trucks rolled out the gate like a strike team on a mission. Each one was loaded up with chemicals to take on their common foe — the mosquito.

After leaving the Shasta Mosquito and Vector Control District headquarters north of Anderson, the trucks split up and headed for different parts of Redding, Anderson and Shasta Lake to cruise through key neighborhoods.

Each truck carried pesticide and a fogger in the back that sends a plume of mosquito killer some 15 feet into the air and spreads out about 300 feet in all directions.

When the pesticide — in this case Permex 30-30 — comes in contact with mosquitoes, it kills them, said Mosquito District Manager Peter Bonkrude.

Thursday night’s fogging run marked only the second one this year, Bonkrude said. Cool, wet and windy weather has kept crews from effectively using the foggers, he said.

But it’s the wet weather that drives the need for more fogging. The heavy rainfall this past winter has left plenty of standing water, creating good breeding conditions for mosquitoes.

"Those mosquitoes are probably the highest we’ve seen in a long time,” Bonkrude said of the types of mosquitoes that grow in standing water. “We’re already seeing increases in our mosquito traps that we have placed throughout our district, and we definitely anticipate those numbers above what we normally see in our area.”

Another type of mosquito grows in tree holes. They come out in the morning and evening to buzz and bite, which is why the district sends its trucks out in the evening and early mornings.

The pesticide used in the fogger was 30 percent permethrin, according to the manufacturer. Bonkrude said the small amount of pesticide used in ultra-low volume foggers is not dangerous to other bugs or humans.

But if drivers see someone walking along a road, they will stop fogging until the person passes by, he said.

Mosquitoes pose a risk for carrying West Nile virus, Saint Louis encephalitis and potentially dengue, chikungunya and Zika viruses, according to the Mosquito and Vector Control Association of California.

Of those, only West Nile virus has been seen in Shasta County in recent years, according to the California Department of Public Health.

In the past five years there have been eight cases of West Nile virus in humans in the county, according to the state. So far this year there has been one reported human case of West Nile virus statewide (in Kings County), but none so far in Shasta County.

Saint Louis encephalitis hasn’t been seen in mosquitoes in the county since 1997.

Mosquitoes that carry the Zika virus have been found in other areas of the state, but not in Shasta County.

As of April 21, the state reported 534 travel-related cases of Zika in humans — none in Shasta County or elsewhere in the North State. There have been five reported cases of babies born with birth defects — brain damage including microcephaly — caused by Zika.

The tree hole mosquito also carries canine heartworms, a serious health threat to dogs. The best way to protect dogs from this is to give them heartworm prevention medication.

In addition to sending out its fog trucks, the district also sprays areas with standing water and removes standing water and other places where mosquitoes grow.

They also place pesticides in tree holes to kill mosquitoes. Bonkrude said they focus on trees in parks and other areas where people gather.

Last year the district had more than 800 requests to treat mosquitoes on private property and will deliver fish that eat mosquito larvae in ponds and livestock troughs.

District residents can sign up for email and telephone text notification about fogging activity.

During the warmer months the district also conducts aerial surveys, looking for swimming pools that have turned green and become a breeding ground for mosquitoes.

In 2016, the survey found 727 pools that were dirty and needed further inspection. In 2015 the survey found 325 pools that needed follow-up.

Mosquito officials urge residents to eliminate standing water on their property, including flower pots, old tires and buckets. Mosquitoes can lay eggs in water sources as small as a bottle cap, the Mosquito District Association said.

People should install screens on all windows and doors. And when going outdoors, people are urged to wear long sleeves and pants, as well as apply insect repellent.

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