An all-out attack combining ground and aerial spraying began this week in the Baker Valley Vector Control District’s fight against an exploding population of mosquitoes.
A mirror image of the Elkhorn Mountains reflected Tuesday in a flooded pasture north of Baker City along Slough Road while pilot Tim Metivier sprayed the area with larvicide from his Cessna 188 spray plane as part of the Baker Valley Vector Control District’s war on mosquitoes. (Baker City Herald/Ed Merriman)
A series of thundershowers last week that inundated farm fields and pastures across the Baker and Keating valleys and other lowland areas, followed by warm weather this week, has created ideal hatching conditions for eggs laid last fall by floodwater mosquitoes, said Jim Lunders, manager of the vector control district.
Mosquito eggs laid 15 to 20 years ago have also hatched in areas where standing water is rare, Lunders said.“If people see flooding not normal in their area, let us know,” he said. “I have a feeling we are going to have a lot of mosquitoes hatching in areas we normally don’t.”
While the recent heavy rains combined with widespread flood irrigation are likely to produce a lot of floodwater mosquitoes, Lunders said a greater danger lies ahead when culex mosquitoes, which carry the West Nile virus, start hatching.
“Flood mosquitoes are a nuisance and an economic problem, but they’re not a health problem like the culex mosquitoes” — including the culex pipiens variety that Lunders expects to start hatching inside the Baker City limits in the next few weeks.
Culex pipiens mosquitoes pose the greatest risk to city residents because the insects lay their eggs in water found in urban areas in buckets, wheelbarrows, used tires, bird baths and other containers.
“I’m bracing myself for a bad container mosquito year in town,” Lunders said. “I know a lot of 5-gallon containers won’t get turned over this year, and that’s not good.
“One 5-gallon bucket with 4 inches of water left next to the patio can produce 300 mosquitoes a day,” he said.
“The reason it’s so important to turn over containers in town is because every one of the mosquitoes in those containers are most likely going to be culex mosquitoes,” Lunders said. “They lay eggs in pretty much anything that can hold water.”
Mike Borisoff, a former Vector Control District employee who lives in Baker City, said he recently found hundreds of mosquito larvae in a landscaping pond in the yard of a vacant home in his neighborhood around Ninth and Church streets.
The water in the pond was about 14 inches deep, Borisoff said. And that was before last week’s downpours.
He also found larvae in buckets and flower pots.
“Everywhere I looked with water there were mosquitoes,” he said.
Borisoff pointed out that even plastic tarps can hold pockets of water that serve as mosquito incubators.
Tires are particularly inviting for the insects, he said, because their black surface acts as a sort of “heat sink” that speeds the mosquitoes’ growth cycle.
Regionally, Lunders said culex mosquitoes are hatching early this spring, and in the Columbia Basin near the Tri-Cities, some culex mosquitoes have already tested positive for West Nile virus.
Reports of mosquitoes carrying West Nile virus in Baker County typically run three to four weeks behind the Columbia Basin, Lunders said.
While the vector control district’s property tax-funded budget is sufficient to deal pretty well with flood mosquitoes, Lunders said money’s been tight since culex mosquitoes carrying West Nile virus arrived in the area about four years ago.
“We are not in very good shape financially right now,” Lunders said. “Dealing with West Nile every year is expensive. That’s hit us pretty hard.”
Application costs for spraying pesticides have doubled, but Lunders said his budget has risen just $8,000, from $310,000 for the current fiscal year to $318,000 for the 2009-2010 fiscal year that begins July 1.
The district cut its contingency fund from $211,000 in the current budget to $161,000, which Lunders said is the bare minimum needed to sustain spray programs until the first tax revenues for 2009-2010 arrive in October.
“West Nile is draining our contingency fund,” Lunders said. “I’d love to kill every mosquito out there that ever hatched from an egg, but that’s not going to happen.
“I’m in a situation now where I have to prioritize. I’d love to spray larvicide on 20,000 acres, but I’ll be lucky to cover 6,500 acres. I have to pick and choose what acres to treat that will have the most impact,” Lunders said.
“Every plane take-off costs $1,800” for aerial applications of (Vectobac) larvicide, and later on when aerial spraying of adult mosquitoes with the pesticide Dibrome is required, each plane take-off costs $17,632, Lunders said.
If people would be vigilant about emptying buckets and other containers that hold water, Lunders said there’d be a lot fewer adult mosquitoes flying around Baker City.
Area residents are asked to look for mosquito larvae or baby mosquitoes and call BVVCD, 523-1151, if they see any larvae floating in standing water.
Lunders also encourages people to call BVVCD if they notice large numbers of adult mosquitoes around their yards, because that information will help the district’s staff locate and treat breeding grounds.
The thunderstorms hampered ground and aerial spraying last week and over the weekend, but the weather cleared up Monday and Tuesday, making larvicide applications possible in Keating Valley and northern Baker Valley.
So far this season, Lunders has been joined in the ground application of larvicide by seasonal staffers JoLynn Neske, a college student who is back for her third summer on mosquito patrol, and rookie David Frazey, who teaches vocational classes at Baker High School during the school year and is trying his hand at mosquito control this summer for the first time.
Neske and Frazey were out on the road Monday and Tuesday dipping cups in ponds and areas where irrigation and flood waters pooled, and where they counted two or more baby mosquitoes per cup, they sprayed Vectobac larvicide granules.
Pilot Tim Metivier made aerial applications this week flying his Cessna 188 Husky spray plane, which carries 800 pounds of larvicide granules loaded into the plane by Becca Fielding.
Metivier said 800 pounds of larvicide applied by air treats about 114 acres.
Later on in the summer when the flood waters clear up, a breed of culex mosquitoes called tarsales is expected to start hatching out in the countryside, extending the West Nile virus threat to areas outside the city, Lunders said.