Asked October 12, 2015, 7:12 PM EDT
Washington County Oregon
Many people in our region have noticed clouds of the same tiny white insects during the past several months. They were recently identified as ash whiteflies, Siphoninus phillyreae, potentially serious pests of ash trees and certain other woody plants. Very little is known at this time about how damaging ash whitefly will be in our region or what sort of management may be needed.
This new webpage (late 2015) for commercial growers has some background information and images of infested leaves: http://oregonstate.edu/dept/nurspest/Ash_whitefly.html. Near the top of the page, notice the link to a local garden show with an interview with an entomologist.
Treatment, if needed, should only be applied when infested leaves are found because that's where the susceptible life stage lives. No action needs to be taken against the flying adults.