While residents gazed toward the sky last week, waiting for planes overhead to resume spraying pesticide, a quieter battle was being waged using trucks on the ground.
Delta breezes had prevented the aerial spraying for days, but the Sacramento-Yolo Mosquito Vector Control District employees used ground-spraying extensively in the Pocket area.
The situation changed Saturday at 8:30 p.m. as planes resumed aerial spraying in south Sacramento for the first time since Aug. 11.
A couple of weeks ago, district officials had covered a large swath in and around Citrus Heights using trucks. And they've ground-sprayed in parts of Galt and in the Elverta-Rio Linda area.
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Tentative plans for the coming two weeks call for hitting several more areas with trucks, including Galt, Davis, Woodland and downtown Sacramento.
"We have consistently done this work in rice fields and agricultural land (in the past), and we have a lot of data from those activities, and it's been very effective," said David Brown, the mosquito district's manager.
Spray applied from trucks contains the same active ingredients as spray applied from the air. The formulation is a little different because it is being applied from a truck going 10 mph instead of a plane going 150 mph, Brown said.
"We've taken these vehicles down to wind tunnels and done tests and determined the best material that creates the best droplet size," said Brown. "The ingredients are still the same - pyrethrins and PBO" (piperonyl butoxide).
Spray from trucks, like the aerial spray, poses no risk to humans, Brown said. However, the same precautions apply: Minimize exposure to the spray by remaining indoors and closing windows.
Additional steps can be taken - covering playground equipment and removing toys from the yard, for example - but they aren't necessary, Brown said.
The district is conducting the spraying to fight infections of West Nile disease. As of late Friday, 58 human cases of the virus had been reported in Sacramento County, the highest number in the state.
The Sacramento-Yolo district launched aerial spraying Aug. 8-10, covering about 50,000 acres in northern Sacramento County. But aerial spraying in southern parts of the county has been hampered since Aug. 11 by brisk Delta winds.
Officials have sprayed from the ground on several nights when they could not spray by air. They finished ground-spraying the Pocket area, for example, while planes weren't flying.
Now, district officials tentatively are planning to start ground-spraying Davis and Woodland in Yolo County. The decision to spray Davis and Woodland from trucks rather than by airplane was based on their geographical size - roughly the size of the Pocket, Brown said.
Woodland resident John Desalernos is happy that the trucks will be coming to his town.
"I think it is necessary," he said Saturday as he sat near downtown Davis. "I think there is a lot of mosquitoes with the weather that we have had - a lot of puddles for them to propagate."
Davis resident Tapua Gwarada said she has been waiting for officials to start spraying in her area for a long time. Calling the planned spraying, "a good thing," she said, "I think they should just do it and get it over with."
Ground spraying isn't quite as unprecedented as aerial spraying in greater Sacramento, but it had been restricted to rural and semirural areas such as Wilton.
"Not in the Pocket area," Brown said. "We haven't done it like that, certainly in recent years."
The vehicles used for ground spraying are normal, midsize trucks, Brown said. They are fitted with a device that, much like an aerosol can, slowly releases pesticide into the air.
At this point, Brown said, it would be best if ground spraying in many parts of Sacramento County supplemented aerial spraying. Applying pesticide from trucks takes a lot longer and it's nearly impossible to cover as much ground.
"We're talking 2,000 square miles," he said. "I can't effectively treat that by ground."
It also takes a lot of drivers. Many drivers work long days on larvicide treatment then go out and spray from trucks at night, when mosquito activity peaks.
"My people are going to burn out," Brown said. "I really want to continue my focus on my larvicide program. I can cover that much more acreage by air and just supplement with quasi-small treatments.
"I can rotate my personnel to do those ground treatments so that I'm not burning them out."
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