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Vector control director describes sudden mosquito explosion, emergency aerial spray and near‑complete mortality
Summary
Northwell Vector Control reported a late‑season mosquito hatch that raised trap counts to thousands per trap; the district used a contingency aerial applicator to treat 15,360 acres, after which mortality trapping returned about 98% adult mortality and one trap tested positive for West Nile virus.
The Northwell Vector Control presenter (identified in the meeting as Greg) told the Morrow County commissioners that a late‑season surge in river water inundation produced an unusually large mosquito hatch and an emergency suppression response.
“We went from that overnight to 3,000 mosquitoes in a trap,” the presenter said, describing routine traps that had previously captured fewer than 100 adults. He told commissioners that other traps showed as many as 6,000 mosquitoes per trap during the event.
The district contracted a contingency fixed‑wing applicator to treat 15,360 acres; post‑mission mortality trapping returned about 98% adult mortality, the presenter said. The district also reported one trap that tested positive for West Nile virus during the season.
Why it matters: The presenter said unusually high John Day Pool river levels flooded low‑lying areas that had not been wet for decades, producing mass hatching of Aedes vexans and related species. Those species are aggressive biters and, in high numbers, present a human‑health nuisance and a secondary risk for vector‑borne disease.
Operational details: The presenter described coordination with neighboring districts and federal agencies and said the district will pursue interagency meetings (including US Fish and Wildlife and EPA representatives) to address recurring flood‑driven mosquito problems tied to reservoir operations. He also described a capital project: the Port of Morrow has deeded three acres for a new vector control facility; bids are out and the project timeline from ground‑breaking is about a year.
Board action and context: Commissioners thanked the presenter for the report and noted interagency support was appreciated at OHV parks and other county facilities. The board did not take formal action on vector control operations at the meeting.
Quote: “Those mosquitoes hatched off… we were getting 6,000 mosquitoes per trap,” the presenter said, summarizing the scale of the event.
