Tiny white moths?
All of a sudden there are thousands of tiny white moth-like creatures in the air, grass and bushes in Lake Oswego. They look like snowflakes but are quite annoying. Do they hurt the foliage? Why are they here? Can they be controlled?
Many other people in our region are seeing similar clouds of the same small white flying insects during the past several months. The insects were recently identified as ash whiteflies, Siphoninus phillyreae, potentially serious pests of woody plants. These insects were first reported to be in the Willamette Valley during 2014. 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 webpage 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 a university entomologist.)
It’s not yet been determined if treatment will be needed during the growing season. If they will be needed, it’s important to know that pesticides are effective only against the new hatchlings but not against the flying adults currently so prevalent. Where the swarms are particularly dense, some people have resorted to using dust masks which are sold by paint and hardware stores.