Emerald Ash Borer (Agrilus planipennis)
by Arboretum Manager, Ric Jordan
The Emerald Ash Borer, a highly destructive insect that targets and kills exclusively ash trees (Fraxinus sp.), has been positively found and identified on the southern outskirts of Guelph, only a few kilometers from the University of Guelph Arboretum.
The insect was introduced from Asia, and is believed to have first come to the U.S. 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 U.S. and Canada. In Windsor, where it was first found in Canada, essentially all ash species but one are dead with the exception of young saplings. The one species that seems to have some form of resistance to the insect is Blue Ash (Fraxinus quadrangulata ) for reasons not clearly understood at present.
In an effort to control or slow the spread of this menace The Canadian Food Inspection Agency 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 please visit CFIA’s website
However even with a penalty of up to $50,000 for violating the ban outbreaks have shown up in the province of Quebec, the Eastern Counties of Ontario, near Sault Ste. Marie and the latest being on Manitoulin Island in early December.
As arborists develop more and better detection techniques it is hoped that the spread will be somewhat controlled or at least slowed. Prism traps assist in alerting us when the insect has arrived in an area and also help in estimating the population. Branch sampling at present seems to be the gold standard in determining if a tree is home to the beetle.
Another sampling technique has been used by a University of Guelph professor, Steve Marshall and grad student, Phil Careless of the School of Environmental Science. Phil uses a wasp species that feeds its young borer beetles. By watching this wasp’s nests, researchers can see if the female wasps bring in any EABs. www.cerceris.info
If discovered when populations are low enough there is a chemical treatment that has good results although no guarantees of long term survival. Other treatments may come on the market but at present the following link describes the one most used: http://www.bioforest.ca/index.cfm?fuseaction=content&menuid=18&pageid=1026
At present the recommendations are for treatments every two years for perhaps 10 years thus not only allowing the wave of infestation to pass but natural predators to move in and help control the insect.
Single eggs are laid in the crevices of ash bark from May to July and hatch in about 3 weeks. The larvae feed on the phloem and sapwood as they grow in size leaving their characteristic serpentine tunnels which, if populations are high enough, will kill the tree within two to three years. The larvae overwinter in the tree and then emerge from April to June, begin mating and then lay their eggs shortly after emerging. Their emergence hole is a distinctive D-shaped hole.
In preparation for the spring of 2012 and going forward The University of Guelph Arboretum has adopted a management plan that will:
- Educate the public on the community impact through the use of fact sheets/brochures/printed material.
- Chemically preserve some of the large ash in our existing woodlots to ensure the ongoing population of naturally occurring ash within our boundaries.
- Strategically treat a selection of ash in our teaching collections that come from wild sources both in North America and around the globe in the Northern Hemisphere.
- Increase scouting and detection within our Blue Ash gene bank in an effort to evaluate its natural resistance to the pest.
- Remove hazard trees along our woodlot and collection trails as required.
As one can imagine all of this comes at a cost. In discussing treatment costs with other institutions and municipalities the average cost is in the $5 - $5.50 per centimeter diameter at breast height (dbh). So for a mature ash with a dbh of 60 cm (24 inches) the cost could run over $300. However one has to compare that with the costs of removal which could run into the thousands. You can imagine the challenge some municipalities are facing when the ash component of the urban forest numbers in the thousands. The City of Guelph has approximately 9000 ash enumerated as street and park trees and another 9000 in woodlots. This does not take into account private home owner’s trees. Like all jurisdictions events such as this are difficult to plan for and over The Arboretum’s 40+ years of existence we have not faced a situation such as this in our budgeting process. At present it does not look like there is any monetary relief being made through provincial resources so we are creating a line item in our budget to reflect money raised and allotted to this plan.
As Arboretum Director Alan Watson was heard to say after returning from a trip to Pelee Island ‘I have seen the future, and it isn’t pretty’ when discussing the effect the insect was having on municipalities and woodlots in that corner of the province. We plan to ‘change the future’ and at least moderate the effects of this destructive alien pest at The Arboretum.