Emerald ash borer
Emerald ash borer (Agrilus planipennis) or EAB, native to Asia, is a woodboring beetle that arrived here accidentally in solid wood packaging material. It attacks ash (Fraxinus) tree species and is a highly effective tree-killer in North America. It has already killed millions of ash trees since it was first detected in Canada in 2002, and is expected to kill billions more.
Emerald ash borer will have a profound economic and ecological impact on ash-rich regions that it invades since all or most ash trees will be killed. Currently, the only option to prevent the trees from dying from EAB attack is to have them injected with an insecticide known to be effective for EAB. Costs of treating ash trees with insecticide, as well as for removing and replacing the EAB-killed trees, can be considerable. Planning in advance of EAB can help you to better achieve your objectives, and decrease the financial impact of this pest.
Female beetles lay their eggs on the surface of the tree's bark. After hatching, the young larvae tunnel through, and feed under, the bark creating an S-shaped gallery. Since the tissue they consume is the tree's vascular tissue, larval feeding damages the tree and eventually kills it. After developing through the pupal stage, the adult beetle bores its way out of the tree leaving a distinctive D-shaped exit hole in the bark. Adult beetles can be seen from May until late summer, depending on weather and climate.
Read more about EAB biology
EAB emerging from infested ash
Video courtesy of Paul Hambidge
Trees at risk
In North America, all native ash trees (Fraxinus), with the possible exception of blue ash (Fraxinus quadrangulata), are at risk. Mountain ash (Sorbus americana) is not a true ash species so will not be attacked by the beetle. Recently, EAB was found in a small number of white fringe trees in Ohio. Research is being initiated to re-examine whether tree species closely related to ash, such as lilac and privet, could be at risk. There is no scientific evidence at this time that EAB will attack tree species other than ash here in Canada.
The range of EAB in Canada continues to expand and the beetle is now found in five provinces. It is established throughout southwestern, central and eastern Ontario, Manitoulin Island, Sault Ste Marie and Thunder Bay in northern Ontario, southwestern Quebec, Winnipeg, Manitoba, several counties in west and southwest New Brunswick, and Halifax County, Nova Scotia. The expanded area regulated for EAB reflects this range expansion.
Ash trees infested by EAB do not begin to decline until a season or more after they have first been colonized by the insect larvae, making it difficult to detect EAB-affected trees at early stages of infestation. When infested, the crown of the tree will start to thin, especially at the top, becoming worse over time. Epicormic shoots may grow from the base of the trunk. The S-shaped larval feeding galleries and the D-shaped adult exit holes (described above) are seen especially at later stages of infestation when these signs are more common at the lower part of the tree trunk. Evidence of woodpeckers visiting the tree to feed on the larvae is often the most distinctive signal of EAB infestation.
Read more about EAB detection
Follow these links to find out more about EAB and what to do:
- For municipal delegates tasked with finding out more about EAB, how it may affect their community, and options for dealing with it.
- For homeowners trying to decide what to do about the ash tree in the yard.
- For rural landowners making decisions about how to manage ash trees in their woodlot, windbreak or yard.
- For land managers responsible for trees on private land such as school grounds, golf courses, or businesses.
Development of this initiative funded by: