People passionate about nature

Watch Out for the Emerald Ash Borer

An unwanted hitchhiker has arrived in Manitoba

By: Leah Hodgson, Invasive Species Centre

Have you heard of the tiny green menace that has been spreading across Canada, leaving a wake of destruction? Emerald ash borer (Agrilus planipennis), also known as EAB, has arrived in Manitoba.

Above: Emerald ash borer adult; Debbie Miller, USDA Forest Service, Bugwood.org

The emerald ash borer is native to parts of Asia and was first detected in North America along the Windsor, Ontario and Detroit, Michigan border in 2002 – although it’s estimated to have been introduced to North America in the 1990s. Since its arrival, EAB has spread across southern Ontario and east into Quebec. In 2018, EAB was confirmed present in Edmunston, New Brunswick and Bedford, Nova Scotia – the first Atlantic Canada sightings. Across the border, emerald ash borer is present throughout 35 states, including Minnesota and South Dakota.  

Above: CFIA-regulated areas in Canada; CFIA, 2019

At only 8-14mm long, this invasive species causes an exponentially disproportionate amount of destruction to Canada’s forests. Adults lay eggs in the crevices of ash tree bark, where larvae will then hatch and bore into the heart of the tree to overwinter. Large populations of EAB larvae feeding under the bark disrupt nutrient and water transport, eventually killing the tree. Depending on seasonal temperature, EAB adults will emerge in late spring, leaving a distinct D-shaped hole in the bark.

Above: EAB larvae and tunnels under bark; David Dutkiewicz, Invasive Species Centre

Winnipeg became a Canadian Food Inspection Agency (CFIA) regulated zone for emerald ash borer in December 2017. It has been estimated by Winnipeg forester Martha Barwinsky that Winnipeg is home to 350,000 green ash trees, all at risk from the invasive beetle. While cold weather may slow population growth, as Manitoba thaws EAB will continue to survive – killing up to 99% of the trees it infests.

Above: Ash crown dieback, yellowing leaves, and rapid growth shoots on lower trunk; David Dutkiewicz, Invasive Species Centre

The impacts of this tiny invader cannot be overstated. Ash trees increase property values, provide windbreak and temperature regulation, create wildlife habitat, and mitigate pollution. The loss of this species represents economic, ecological, cultural, and aesthetic loss for Canadian communities. As habitants of this beautiful province, and Canada as a whole, Manitobans each have a responsibility to watch for signs of this invader and prevent its spread. This means buying local firewood, watching for signs and symptoms of EAB infestation, and reporting any sightings outside of regulated areas to CFIA. Together, we form the best protection against invasive species!

Watch for signs of the emerald ash borer:

Above: Vertical crack in ash bark; David Dutkiewicz, Invasive Species Centre

EAB Adults:

  • - 8-14 mm long
  • - Bright metallic green
  • - Long body with flat head
  • - Abdomen beneath the wings is bright coppery-red

EAB Pupae:

  • - 10-15mm long
  • - Creamy white

EAB Larvae:

  • - 26-32mm long
  • - Creamy white-light green body
  • - Small brown head

Above: D-shaped exit hole; Kenneth R. Law, USDA APHIS PPQ, Bugwood.org

Tree Signs & Symptoms:

  • - D-shaped exit holes
  • - Leaf/crown death
  • - Bark deformities
  • - Woodpecker feeding holes
  • - Yellowing leaves
  • - Vertical cracks in trunk
  • - Rapid growth (epicormic) shoots, most identifiable on the lower trunk
  • - S-shaped larval feeding galleries under bark

Above: Rapid growth shoots on lower trunk; David Dutkiewicz, Invasive Species Centre

Learn more about EAB in Manitoba here.