Emerald Ash Borer beetle wreaks havoc on Scarborough ash trees

The Scarborough Garden and Horticultural Society received a visit from a very “green” guest last Tuesday. Fortunately for them it was guest speaker Erin Silverstein, and not an Emerald Ash Borer beetle.

Silverstein is a University of Toronto graduate and has degree in forestry and geography, with deep environmental focus. She is a part of the organization Local Enhancement and Appreciation of Forests (LEAF). The organization has been dedicated to protecting and improving urban forests since 1996 and has helped plant over 7,000 native trees in the GTA.

A large part of this dedication involves educating the public about environmental factors that impact the city’s urban forests. Scarborough’s pressing issue is a pest called the Emerald Ash Borer (EAB).

The EAB is a tiny metallic green beetle that feeds on and kills all species of ash trees. It is believed to have come from Asia on wood packaging, and was initially discovered in North America in 2002 In Detroit and Windsor.

The bug has four distinct life-cycle stages: egg, larvae, pupae and adulthood. Adults feed on the leaves of the ash. They then lay eggs in the bark, which hatch after just a few weeks. A female can lay up to 275 eggs in one year.

There is little hope for the ash trees in Ontario.

— Erin Silverstein

EAB larvae cause the most harm. As they grow and develop, they burrow into the cambium layer of the tree. The cambium is the living tissue of the tree that allows nutrients and water to move up and down the trunk. With thousands of larvae on any given tree, the vascular system of the tree is cut off and the flow of nutrients is interrupted. Thus, the ash dies.

“This is a huge infestation. It’s all doom and gloom,” said Silverstein. “There is little hope for the ash trees in Ontario. The infestation has spread all throughout Toronto.”

There are approximately 160,000 ash trees in Toronto, making up 8.4 per cent of urban canopy cover in the city. Silverstein says the loss of ash trees is most noticeable in Scarborough and North York and is the most devastating in urban areas. Ash trees were readily planted in the past because of their hardiness and ability to withstand harsh environments.

“Most ash trees are expected to become infested and die by 2017,” Silverstein said. “That’s really not that far away. [The beetle] is a fast-moving killer.”

After Dutch elm disease spread through the city in the ’70s and ’80s and decimated many street elms, one of the favourite trees to replace the Dutch Elm was the ash. Now the ash will be destroyed as well.

“It’s a bad turn of luck that this has happened,” said Silverstein.

Unfortunately, early detection of infestation is extremely difficult. By the time symptoms like bark deformities and s-shaped larvae galleries appear in the tree, it is more than likely too late to be saved.

“After signs and symptoms appear, it means that the tree is too far gone,” said Silverstein.

Silverstein says that even though Southern Ontario’s ash trees are ultimately doomed, there are things we can do to prevent the spread of the Emerald Ash Borer into other areas of the province.

Beetles’ range increased by people

Emerald Ash Borer Quick Facts:

  • The Emerald Ash Borer is a beetle that feeds on and kills all species of Ash trees.
  • It’s colour is an iridescent metallic green.
  • It is 1.25 cm long and .32 cm wide.
  • It was initially discovered in North America in 2002 in Detroit and Windsor.
  • It is believed to have come from Asia on wood packaging/crates.
  • It flies but is so small it is often carried by the wind.
  • Most of its spread is by people moving firewood.
  • Ash trees infested by the Emerald Ash Borer die within 2–3 years.
  • Most Ash trees in Southern Ontario are expected to become infested and die by 2017.

Source: arbordoctor.net

Most of the EAB’s spread is to blame on people moving firewood from their homes in the city to other areas of the province. The Canadian Food Inspection Agency has issued Federal Ministerial Orders that prohibit the movement of firewood from specific areas of Ontario. This is to hopefully keep the beetles out of Northern Ontario.

“Let’s try and save cottage country for now,” said Silverstein.

There is a bio-insecticide available called TreeAzin that can be injected into the base of an ash to kill the beetle and its larvae. However, it is very expensive.

The city is using TreeAzin on a case-by-case basis. They will only inject trees that are large and valuable to the urban canopy. Two thousand trees are slated for injections this May. The city plans to remove dead and dying trees on city property, and will replace them with other species.

Silverstein says scientists in Canada and the U.S. are working on introducing some bio-controls, like a species that would help terminate the Emerald Ash Borer. However, this is very early in research.

Silverstein suggests for homeowners with infested ash trees to look into removal and re-planting options. Have a certified arborist test your soils and recommend which type of tree is best to plant in place of an ash.

“When re-planting, remember the bigger the better,” said Silverstein. “Bigger leaves means more photosynthesis, which increases the canopy cover and ultimately leads to a greener, cleaner environment.”

For more information on the Emerald Ash Borer and LEAF’s initiatives, visit yourleaf.org.

4 comments:

  1. It is not “too late” to save ash trees in southern Ontario!

    A strategic EAB management program, properly implemented, saves ash canopy.

    The Coalition for Urban Ash Tree Conservation published the “EAB Managment Statement” in 2011 which concludes that an ash canopy conservation approach ( blending of treatments and removals) is often economically and ecologically superior to the ash tree removal alone option:
    http://www.emeraldashborer.info/files/conserve_ash.pdf

    The Canadian Forest Service’s “Ash Tree Protection Model”- a tool for the ash tree homeowner shows- shows a net positive benefit for the ‘treatment + removal’ approach over the ‘removal alone’ approach for 20 years:
    http://cfs.nrcan.gc.ca/e-bulletin/5

    Municipalites in southern Ontario such as Burlington, Kitchener, Oakville, Oshawa, Richmond Hill, London and Ottawa , for example, have ash tree treatment programs as part of their EAB management.

    There have been several effective new tools in the EAB management toolbox developed in recent years as the science of EAB management evolves ….much of the ‘information’ in this article does not seem to reflect this.

  2. Not every ash borer is an emerald ash borer!
    But all of them attack our ash trees.
    In front of our house, a very large ash tree is showing signs of decline for over 15 years. The tree is infected by a native ash borer the Redheaded ash borer, Neoclytus acuminatus.
    Excellent information can be found here:
    http://www.emeraldashborer.info/files/e-2939.pdf
    Public information should have been started when the first infected trees where found in Toronto. (highway 401& Sheppard Ave.)

  3. Hi Carleigh,

    Thanks for writing this great and informative piece, and for your contribution to the urban forest. I just wanted to note that it’s actually 17,000 trees and shrubs, rather than 7,000, that LEAF has helped plant across Toronto and the surrounding area since 1996!

    Take care and keep up the great work.

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