Arborists at York University have completed an inventory and assessment of the health and diversity of trees growing on the Keele and Glendon campuses. The inventory and assessment are an integral part of information gathering needed for a long-term strategy to deal with the inevitable destruction of the ash trees growing on the campuses by the Emerald Ash Borer (EAB).
The insect, an invasive species with no natural predators in North America , was introduced from Asia. It is believed to have arrived in the United States in a shipment of untreated wooden pallet boxes from China. Since it was spotted in 2002, it has spread rapidly, killing millions of ash trees in the US and Canada.
When bark is removed, ‘S-shaped’ EAB larvae galleries become apparent. It is this damage that disrupts the tree’s vascular system of the and leads to eventual death
In Windsor, Ont., where it was first found in Canada, the EAB has destroyed the majority of the species of ash trees, with the exception of the blue ash (Fraxinus quadrangulata). In an effort to control or at best slow the spread of this menace, The Canadian Food Inspection Agency (CFIA) — the federal agency responsible for dealing with the such infestations — has embargoed the movement of firewood, nursery stock and mulch from regulated areas of known infestation to areas free of the pest. To see a map of regulated areas, click here.
“In 2002, no one knew what was killing the ash trees in the state of Michigan and Windsor, Ontario,” says John Wilson, manager of campus construction and mailing services, and a certified arborist. “We now know that the Emerald Ash Borer is responsible for the wide spread decline and death of ash trees in that area and has now spread to the Greater Toronto Area, and beyond. Latest reports from CFIA indicate the borer has been found as far west as Sault Ste. Marie and as far east as Laval, Quebec. ”
EAB infested trees by Ian Macdonald Blvd. and Chimneystack Rd. soon to be removed. Photo was taken in Sept. 2012. The first sign of canopy decline appeared in Aug. 2011.
In anticipation of EAB attacking ash trees growing on York’s campuses, Tim Haagsma, manager of Grounds, Fleet & Waste Management, worked with Wilson to develop an immediate strategy. They received some help from Leo Rocc, a forestry student intern from the University of Toronto. Together, the group developed a practical and proactive action plan to deal with EAB.
The suspicion that the EAB was already making its presence known on the Keele campus was confirmed in late June. Adult EAB beetles were seen on trees just east of Ian Macdonald Blvd. north of Chimneystack Rd. Once infested, trees decline and die within a one- to three-year period.
The adult female EAB burrows into trees to lay eggs. The larvae then feed on the tree, ultimately plugging and injuring the tree’s connective tissues, which in turn prevents water and nutrients from circulating within the tree. Adult borers surface from the tree in the spring after leaves have emerged. When the insect chews its way through the bark, it leaves a “D” shaped exit hole, which is evidence of infestation. The canopy of an infected tree shows decline. Dead trees become dry and brittle in a very short time, which poses a serious safety threat. Identifying infested trees and promptly removing them is a vital part of any management plan.
An ash tree located southeast of Osgoode Hall Law School, one of the 32 trees injected with TreeAzin to combat EAB infestation
As part of their strategy, Haagsma and Wilson were able to secure funding to have 32 trees treated with a chemical called TreeAzin, a natural and safe bio-insecticide made from the seeds of the Neem tree. TreeAzin, which must be applied by a trained technician, has been approved by the provincial government for use against EAB and provides two years of protection before it must be reapplied. Injection costs are $7 per centimetre of the tree’s trunk diameter. The average cost to inject the 32 trees on the Keele campus was approximately $300. In many cases, treating large healthy ash trees in strategic locations can be both environmentally and economically justified when compared to the cost of removing and replacing mature trees.
Another element of the action plan will see an additional 32 trees injected with TreeAzin next spring.
Emerald Ash Borer. Photo: Wikimedia Commons
Since it is a fact that untreated trees will eventually die, Haagsma and Wilson’s plan also involves removing and replacing the remaining ash trees over the next five years.
“As a result of the inventory we know that approximately 1.5 per cent of the 97,000 trees that make up York University’s urban forest are ash. This is actually good news,” says Wilson. “In some municipalities in Canada, ash trees account for more than 10 per cent of the urban tree population. There are 519 trees in our open areas and another 800 trees within our four woodlots.”
Another part of next spring’s activity will see the creation of a nursery that will be specifically stocked with a variety of tree species native to the region, says Wilson. The intent is to provide more diversity and stability for the University’s existing tree canopy.
An EAB web page on the University website is in the process of being created to provide regular bulletins to the York community. Until then, Wilson and Haagsma have put together a list of web resources:
- The Canadian Food Inspection Agency
- Bioforest Technologies Inc. (for information on TreeAzin insecticide)
- The City of Toronto Urban Forest (for information on the city’s plan to deal with the Emerald Ash Borer)
- The Emerald Ash Borer Coalition website
- Jim Zwack, a tree expert with the GTA based company Davey Tree, has created a video overview about the EAB
- The Town of Oakville has prepared two videos on the EAB, Emerald Ash Borer 1 and Emerald Ash Borer 2.