COEUR d’ALENE — The smoky-winged ash aphids are back, and experts say there is not much you can do to control the pesky insects once they take flight.

“It’s pretty tough to get rid of them, especially at this juncture,” said Kenny Bartlett, who has been a licensed pest control operator for 20 years. “Flying insects that are not in their nest are tough to control.”

Bartlett said the aphids begin to swarm ash trees usually at the end of September, and usually last until a hard freeze occurs. He said their life cycle at the adult flying stage is about one month.

Bartlett said there are hundreds of species of aphids, but most of them don't have wings.

“We tend to notice the ash aphids more than the others because they fly,” he said, adding they are more prominent in the newer neighborhoods like Coeur d’Alene Place because a bunch of ash trees are planted there.

“They are just going to keep getting worse as people continue planting ash trees,” he said, adding the best way to deal with them is to call a tree company to come out and treat the trees. “Then hope your neighbor doesn’t plant an ash tree.”

Shawn Bennett, a certified arborist with Grace Tree Service, published a column on the ash aphids in The Press last fall.

“We don’t see many of these pests during the year, as they spend four to five months on an alternate host, Douglas fir. In the warm evenings of autumn, they collect on the trunks of ash trees in a mating aggregation,” he said in the column. “This basic bug orgy is more of a nuisance than anything harmful at this point, however, the eggs that are laid in the bark will hatch.

"The eggs will hatch in the spring and can cause damage to the leaves by curling them, and cause yellowing to Douglas fir later in the spring when they return to their alternate host,” Bennett said.

“The gathering of these bugs on the ash can become so thick this time of year that the trunks look as if they are covered with a fuzzy, blue-gray felt,” he said. “Most people just spray them off with water, but to prevent the leaf damage to the ash, it’s best to spray the trunks with dormant oil in the spring.”

Spraying the trees with water works best in the early morning or late evening hours when the aphids are dormant. The oil treatment in the spring will cook the eggs before they hatch.

Bartlett said there are also products like Merit Tree Spray, which is absorbed through the tree roots.

“But dormant spray is probably the best option,” he said.