Portland's Mosquito Infestation Linked to Lack of County Spraying and Warm Spring Season.
Portland is experiencing a surge in mosquito populations, with five times the typical number for mid-June. The county was unable to treat large areas with BTI, which is standardly used for mosquito control, due to regulatory issues. The warm spring caused mountain snowpack to melt earlier than usual, which in turn overflowed portions of the Willamette and Columbia Rivers, creating standing water in which mosquitoes breed. To prevent mosquito breeding and biting, Vector Control recommends emptying out standing water, wearing long sleeves and pants, and applying mosquito repellent.