Current Tree and Shrub Issues




2-lined chestnut borer.


This is a small wood boring beetle that typically invades stressed oak trees in southern Manitoba and elsewhere in the United States. Oak trees in urban areas and on rural acreages easily become stressed through construction impacts – especially housing – on the oaks’ root systems, through altered land drainage projects that flood out oak stands, and through storage of equipment, hard impenetrable materials over the trees’ root systems.


Construction damage stress to the roots near an oak can cause die back of the branches that is not necessarily related to the insect. However, the borer does eventually find a stressed oak tree, however caused, and will bore into the upper twigs and branches to start its feeding and breeding cycles. It is well known that stored oak firewood will be attractive to adult beetles that will bore into them and produce egg galleries. Pruning two-lined chestnut borer infested branches must start early preferably after the damage first shows up.


Typically the adults feed on living oak wood in the cambial area just under the bark during the summer. It is important that stored oak wood must be covered with plastic sheets such as tarps. This will prevent the adults from entering stored recently cut oak wood and starting egg laying larval galleries. The tarp will also prevent adult beetles in the wood to leave and re-infest trees elsewhere.


Pruning early borer infested wood is essential as part of the borer control program. Contact me if you would like to know more about control procedures as this is a very difficult insect to control as pruning dying and dead wood in the tops of the trees alone cannot control the borers.



2014-08-24 Early 2-lined chestnut borer infestation damage; controllable

Very early feeding at the top of the tree’s crown by the two-lined chestnut borer.



2014-08-24 Advanced 2-lined chestnut borer infestation; oak is dying

Advanced feeding at the top of an oak tree by the two-lined chestnut borer



59 2-lined chestnut borer

Two-lined chestnut borer adult

Bur Oak stressed from advanced 2-lined chestnut borer; cannot be controlled at this stage