The smokey-winged ash aphid – that little gray-blue critter flittering around tree-lined residential areas in the Inland Northwest this month – is a harmless but sometimes annoying insect that typically emerges when the weather turns cooler in October, a plant expert said Tuesday.
Dan Lambert, a plant clinic specialist for the Washington State University Master Gardener program in Spokane County, said the aphids come out of the ground this time of year to complete their life cycles by moving from the ground into ash trees where they mate and lay eggs.
Their autumn massing is triggered by humidity, air pressure and day length.
The aphids feed in mature firs in the spring and then go underground during summer where they reproduce asexually. While they might seem to be a nuisance, they are considered to be a part of the natural life cycle in the Inland Northwest and are best left alone, he said.
“It’s one of those environmental wonders,” he said.