Trees sprayed for elm bark beetles


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This article was published 04/09/2020 (751 days ago), so information in it may no longer be current.

City crews were out in South Osborne this past week, spraying trees for a beetle that spreads Dutch elm disease.

The insecticide Pyrate 480 EC (chlorpyrifos) is sprayed directly onto the lower 50 centimetres of each American elm tree trunk, according to David Wade with the City of Winnipeg’s insect control branch.

“There are two or three species of beetle which burrow into the bark at the base of the tree to overwinter,” Wade said. “The beetles carry a fungus that causes Dutch elm disease.”

The Dutch elm disease fungus was introduced into North America in the early 1900s via infected elm wood transported from overseas, and which was first identified in Manitoba in the mid-1970s.

The beetle larvae burrow under the bark and create “feeding galleries” where they also transmit the ophiostoma novo-ulmi fungus to the tree. The first sign of Dutch elm disease shows up mid-summer, according to Wade, when leaves on the affected trees turn yellow.

Weather permitting, the insect control branch crews will treat approximately 10,000 trees. They can’t treat the trees if it’s too windy or raining.

“In combination with the city forestry crews removing elms which have the disease, and our spraying, we are slowing the mortality rate of the elms,” Wade said, adding that homeowners can help keep their trees healthy by watering and fertilizing.

It also helps to spray the elms with a biological insecticide in the spring, when the caterpillars stress the elms by eating the leaves, he said.

Pyrate 480 EC has been approved for use in Canada by Health Canada’s Pest Management Regulatory Agency and will be used in accordance with federally approved label directions by licensed pesticide applicators.

Weekly public service announcements will be issued by the city on Fridays throughout the program indicating which insect management areas will be treated the following week.

Sou'wester Insecticide is applied to the base of an elm tree in Riverview to kill the elm bark beetles.

Treatment will occur between the hours of 5:30 a.m. and 6:30 p.m. Monday to Friday, weather permitting.

For more information, contact 311 or visit the city’s insect control website at


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