Conservationists scramble to protect Rattray Marsh from emerald ash borer
80% of trees in conservation area vulnerable to killer insect

Bramptonguardian.com
April 19, 2014
By David Paterson

Credit Valley Conservation is sounding the alarm over a growing threat to Rattray Marsh, one of the most popular green spaces in Mississauga.

CVC says the vast majority of trees in the conservation area are at risk from infestation by emerald ash borer, an invasive insect that kills almost every ash tree it comes into contact with, and it is calling on the public to help it fight back. 

The bug arrived in Mississauga in 2008 and has since been wreaking havoc on the ash tree population. While ash accounts for roughly 10 per cent of Mississauga's tree canopy, CVC says that in Rattray Marsh it's more like 80 per cent.

That makes the conservation area an all-you-can-eat buffet for the emerald ash borer, whose larvae slowly kill ash trees by feeding on layers beneath the bark that are vital for moving nutrients and water.

For several years CVC managers have been monitoring the alarming spread of the pest, which was first picked up in Windsor in 2005 and has since been moving northward deep into Ontario. Already a handful of the ash trees at Rattray have been infested and without action it will likely kill the majority of ash trees in the marsh.

CVC has now embarked on a program to inoculate healthy trees at Rattray using a compound called TreeAzin, which is derived from the seeds of the tropical Neem tree. Partly developed by Natural Resources Canada, it is injected into the trunk and inhibits the growth of the larvae.

"What we are hoping is that by treating ash trees and also removing trees that have already been infested, the area won't be hospitable for emerald ash borer anymore and they will move on," said Jon MacMull, a spokesperson for CVC.

But at an average cost of $200 per treatment, CVC is facing a hefty bill to protect the ash trees on the 81-acre site. Although an exact figure for the costs of the treatment program was not available, the City of Mississauga says that it has to find $51 million to fund its 10-year plan to treat 20,000 municipally owned trees and remove or replace ones already damaged.

City Council decided to institute a special tax levy to pay for the program but as that's not an option for CVC, it is now reaching out to Rattray's 40,000 annual visitors to help raise funds to pay for the work and recently launched a campaign to publicize the threat to the marsh.

"We're calling on everyone who visits Rattray Marsh to do what they can to save our ash," said MacMull, adding that CVC also wants them on board with the effort to replace trees lost to the infestation.

CVC is planning to hold an information session for residents who live near Rattray Marsh at the end of April in an effort win over their support for measures it is putting in place.

"Rattray Marsh is a community resource. There are going to be some changes because of emerald ash borer and we want to get the community behind the work that we and they, together, are going to be doing to help fight this infestation," said MacMull.  

The information session will be held on April 28 at Green Glade Senior Public School (1550 Green Glade) at 7 p.m.

BATTLING THE BORER
- Mississauga has over 100,000 ash trees on City property. It has started a 10-year program to treat 20,000 of them with insecticide. Dying trees have already been removed in several parks, including Cawthra, Kenollie and Huron.
- The emerald ash borer is native to East Asian and likely reached North America in infested packing crates. It was first detected in Windsor in 2005 and is spreading north. By 2013 it had reached Manitoulin Island.
- The Canadian Forest Service estimates that Canadian municipalities face a bill of $2 billion over the next 30 years to treat, remove and replace all the ash trees affected.