▶️ Four Rivers Vector Control getting ahead of big mosquito larval hatch


With warmer weather comes mosquito season. This season in Central Oregon is expected to have a larger larval hatch than usual.

“Along the little Deschutes River, the water got higher in the wetlands than it has in a few years and hatched out a lot of dormant eggs. So right now, we’re just busy mopping them up and controlling them to be the best of our ability,” manager of Four Rivers Vector Control District Chad Stubblefield said.

The team uses a naturally occurring bacteria called “bacillus thuringiensis israelensis” (BTI) to kill larvae before they develop into adults. BTI specifically targets and only affects mosquito, black fly, and fungus gnat larvae. It does not harm the environment or other wildlife.

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They use white cups on the end of sticks, called “dip cups,” to scoop samples out of wetlands and evaluate the mosquito larvae population before spraying BTI in the area.

Mosquito eggs can lay dormant for 10-15 years during dry periods, waiting for stagnant water to cover them, creating ideal conditions. Females can lay up to 1,000 eggs in a 7-10 day lifespan. 

“I know a lot of folks are concerned about the number of mosquitoes out here, but repellent makes all the difference in the world,” Stubblefield said. “DEET oil- lemon eucalyptus is a natural alternative. Picaridin is another good one. Just be patient with us because it’s just now getting warm enough at night for us to do our job.”

Four Rivers Vector Control District uses boats, helicopters, and drones to sweep larger mosquito breeding grounds if necessary. 


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