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This article was published 6/6/2017 (1564 days ago), so information in it may no longer be current.
The tiny, nondescript pests spend their summers on the underside of Winnipeg's leaves, piercing them and sucking out the sugary sap inside. When they finish feasting, the aphids do what you'd expect: they excrete, and they leave behind a sticky coating on your car.
"It's just aphid poo," said Jordan Bannerman, an instructor at the University of Manitoba specializing in aphid parisitoids and biological control of agricultural pests.
The aphid population in Winnipeg usually jumps in June, and the numbers remain high through the summer months.
In Manitoba, aphids can have detrimental effects on crops such as cereal grains and soy beans, but they don't pose any significant threat to trees.
Ken Nawolsky, the city's superintendent of insect control, said that given the relatively low damage that occurs, the aphids don't warrant a widespread response.
Even if aphids are removed from the trees, there's not much hope for keeping them away.
Bannerman said aphids are some of the faster reproducers in the insect world, taking only one week to reach maturity. During the summer stage of aphid development, that reproduction is done through cloning; females are "essentially born pregnant," so within a week they give birth to an identical copy.
"You can never get rid of the aphids," Bannerman said ominously. "You can only limit their numbers."
Nawolsky echoed Bannerman's thoughts.
Though aphids leave cars sticky and sidewalk cement darker with their honeydew residue, Nawolsky and the city are focused on controlling the recent forest tent caterpillar population explosion.
While the aphids suck on leaves, the caterpillars are less careful, biting holes through foliage.
The forest tent caterpillar control program began on May 11, with nightly spraying of trees to remove the bugs from the branches and trunks.
If the caterpillars look new, it's because they last migrated through Manitoba about 15 years ago, Nawolsky said.
"It's our turn to deal with them now," he said.
Luckily, the forest tent caterpillar has a three-year life cycle, and the feeding stage is nearing its close. By the end of the week, the caterpillars will begin the next stage, forming a cocoon and emerging later in the month as moths, he said.
Because the caterpillars aren't frequent visitors to the city, the control program is being funded through the insect control reserve, money allocated specifically to deal with waves of insects such as this one.
Until spraying is complete, Nawolsky said he can't accurately estimate the total cost of the program.
He emphasized one point: the caterpillars, aphids and the cankerworms that dangle from Winnipeg's branches and feed on its leaves don't do any lasting damage. Any defoliation is short-lived, and any honeydew on vehicle windshields can be washed off with high-pressure water.
Bannerman noted that the presence of the insects doesn't pose any health threats to humans.
"They just make a mess. A sticky, mouldy mess," he said.
Ben Waldman covers a little bit of everything for the Free Press.