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The problem lasts months at a time, and while it’s not the worst thing that could happen, “it is a major inconvenience,” Coll said.

“You get out of your car and sometimes you have it dripping on you and you take the dog for a walk and you look at their paws when they come inside and it’s caked with the stuff,” he said. “It’s gross, really.”

Coll is asking city staff to do something — spray the trees with pesticide, release swarms of ladybugs or thin and replace some of the trees with other varieties to reduce their attractiveness to aphids. In fairness, that’s pretty much what the city has been doing, as Amit Gandha, a city arborist, explained.

Staff begin by counting the aphids on leaves to find out whether the trees on a given block are infested. If they are, the block will be scheduled for spraying with an insecticidal soap. Incidentally, Coll’s block is on that schedule, and Gandha recognized it by name.

The spray chokes the pests and brings their population down, but the trouble is that aphids reproduce regularly and “just when you’ve done that, there’s more,” Gandha said.

Another control method is to release “biological-control agents,” which in simple terms refer to predatory insects. The city has tried that, too.

“Certain ones we would not release are wasps, because that starts to have other issues like public safety. But ladybugs, we’ve used them many times. They just don’t seem to be able to keep up.”

Photo by Gerry Kahrmann / PNG

There is another option available after staff have tried everything they could — get rid of the trees.