Vector Control anticipates an average mosquito season for Union & Baker Counties
By Garrett Christensen on Wednesday, April 16th, 2025 in More Top Stories Northeastern Oregon News
UNION & BAKER COUNTIES – Spring is here, with summer not too far behind, and that means the mosquitos are starting to stir. So far, temperatures and moisture levels have been pointing toward an unremarkable mosquito season. Though conditions can quickly change, and the volume and aggressiveness of the bugs could shift in the coming months, Union and Baker County Vector Controls are preparing for what seems to be an average year of mosquitoes.
As temperatures continue to warm, both counties will likely see a routine uptick in mosquito activity as hibernation ends. Mosquitoes that were able to winter as adults will enter a short burst of aggressiveness before attempting to lay eggs and die off. As explained by Union County Vector Control Manager Chris Law:
“Right now, we’re probably going to see a lot of them coming out, but they’ll live pretty short, three to five days, and then they’ll be gone as long as they don’t get a blood meal and find some water to lay their eggs in. That’s why it’s critical that people look around their property, try and find containers that the rainfall is collecting in, and try to dump those out and keep them empty.”
Following the post hibernation activity, mosquito numbers and aggressiveness will likely settle down until temperatures increase over the summer and stagnant water sources begin cropping up, before tapering again in September. For Union County, according to Law, flooding on the Grande Ronde Valley floor is slightly lower than normal, but high elevation snowpack melting off could potentially increase flooding in lower areas of the valley, particularly near the rivers. This will in turn impact water sources, and mosquito breeding, throughout the county.
For Baker County, reservoir levels and snowpack are generally adequate, which could impact mosquito populations once irrigation begins in earnest. The more water left in fields later in the season, the more potential for different mosquitoes, in addition to those that breed from natural floodwaters. As explained by Baker Valley Vector Control Manager Matthew Hutchinson:
“If there is more irrigation water to go out, it also has an effect on some of our permanent water sources. Fields might stay wet longer and it can start growing different kinds of mosquitoes if that water stays out there for a longer period of time. Whereas if it’s just a shorter period of time, a lot of times it’s just floodwater mosquitoes. In general, I’d say I’m expecting a pretty average year to maybe slightly above average.”
Though a nuisance throughout spring and summer, mosquitoes won’t be vectors for sickness until later in the season, around June or July. Only about two local mosquito species of the Culex family can transmit West Nile Virus (itself an avian disease). Those species generally don’t arrive until the summer. That said, for pet and livestock owners concerned about the virus, consulting with a vet to get them vaccinated early is generally recommended as it can allow for a buildup of immunity prior to summer exposure.
Aside from West Nile Virus, no other mosquito born illnesses are on Vector Control’s radar. In Baker County, mosquito pools are tested for Western Equine Encephalitis and St. Louis Encephalitis when testing for West Nile, though the other diseases don’t frequently appear. Law also mentioned that a new species of mosquito, Aedes Aegypti, capable of transmitting other diseases such as Zika Virus has been found in Southwest Oregon but has not been identified in Eastern Oregon.
When mosquito activity and potential for West Nile does begin to increase in late June and early July, vector control agencies will generally begin testing pools on an as-needed basis. Baker County Vector Control is currently working larviciding and did get an upgrade last year in the form of a new treatment drone. Once licensing is complete, the drone will be used to treat larval and water sources.
Aside from vector control activities, the community can do their part in reducing mosquito numbers by getting rid of stagnant water sources. Pet dishes, empty flowerpots, outdoor kid’s toys, practically anything that could hold a small stagnant pool of water could be host to mosquito eggs and should be dried out, or least washed out regularly.
Residents can protect themselves from mosquitoes by ensuring screen doors and windows are in good repair, wearing EPA approved bug repellent, wearing pants and long sleeve shirts when in mosquito heavy areas, and staying inside during peak mosquito hours at dawn and dusk. Even wearing natural colored clothing to avoid visually standing out can help mitigate mosquito bites.
To report mosquito issues or submit service requests, see local vector control offices at:
Union County: https://unioncountyor.gov/vector-control/
Baker County: https://www.bvvcd.org/
Union County Vector Control is also hiring. Contact Chris Law at 541-963-2974 for more information.
